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2015 Mid-Year Report

Jack Haiston, jhaiston@outlook.com , (970) 420-0943 Tyler Norris, tnorris93@me.com, (513) 288-0258

Loren Christensen, lchristensen92@gmail.com, (719) 580-0750 Nathan Houser, nthnhsr@rams.colostate.edu, (970) 631-4734 Andrew Sullivan, asulliv@rams.colostate.edu, (970) 381-4533

Darrin Minnard, dminnard@rams.colostate.edu, (303) 921-6951 Phil Meister, pem572@rams.colostate.edu, (802) 598-2131

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Table of Contents 1.0 Introduction ............................................................................................................................... 5

2.0 Problem Statement .................................................................................................................... 6

3.0 Objectives ................................................................................................................................. 6

4.0 Constraints ................................................................................................................................ 7

5.0 Design Summary ....................................................................................................................... 8

5.1 Electrical................................................................................................................................ 8

5.2 Accumulator Case ................................................................................................................. 8

5.3 Drivetrain .............................................................................................................................. 9

5.4 Suspension ............................................................................................................................. 9

5.5 Aerodynamics ...................................................................................................................... 10

6.0 Design Decisions .................................................................................................................... 11

6.1 Electrical.............................................................................................................................. 11

6.2 Accumulator Case ............................................................................................................... 12

6.2.1 Accumulator Case Material Type ................................................................................. 12

6.2.2 Accumulator Case Size ................................................................................................. 12

6.3 Drivetrain ............................................................................................................................ 13

6.3.1 Motor Type/Model ....................................................................................................... 13

6.3.2 Chain Adjustment ......................................................................................................... 13

6.3.3 Gear ratio ...................................................................................................................... 14

6.4 Suspension ........................................................................................................................... 15

6.4.1 Suspension Points and Kinematics ............................................................................... 15

6.4.2 Control Arm Components ............................................................................................ 15

6.4.3 Rocker Design .............................................................................................................. 15

6.4.4 Anti-Roll ....................................................................................................................... 16

6.5 Aerodynamics ...................................................................................................................... 16

6.5.1 Sidepod Decision .......................................................................................................... 17

6.5.2 Composite Material Decision ....................................................................................... 17

7.0 At-risk Items and Mitigation Plan........................................................................................... 18

7.1 Funding................................................................................................................................ 18

7.1.1 Competition .................................................................................................................. 18

7.1.2 Motor and BMS ............................................................................................................ 18

7.1.3 Chassis Manufacturing and Machining Stock .............................................................. 18

7.2 Manufacturing Capabilities ................................................................................................. 19

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7.2.1 Suspension .................................................................................................................... 19

7.2.2 Battery .......................................................................................................................... 19

7.3 Sidepod ................................................................................................................................ 19

8.0 Final Concepts ........................................................................................................................ 19

8.1 Electrical.............................................................................................................................. 19

8.2 Accumulator Case ............................................................................................................... 22

8.3 Drivetrain ............................................................................................................................ 24

8.4 Suspension ........................................................................................................................... 27

8.5 Aerodynamics ...................................................................................................................... 28

8.5.1 Meshing Analysis ......................................................................................................... 28

8.5.2 Stress Analysis .............................................................................................................. 28

8.5.3 Airflow Analysis........................................................................................................... 29

9.0 FMEA ..................................................................................................................................... 33

10.0 Design for X .......................................................................................................................... 33

10.1 Cost.................................................................................................................................... 33

10.2 Competition ....................................................................................................................... 33

10.3 Data Collection .................................................................................................................. 33

10.4 Manufacturability .............................................................................................................. 34

11.0 Validation .............................................................................................................................. 34

11.1 Electrical ............................................................................................................................ 34

11.1.1 Simulation ................................................................................................................... 34

11.1.2 Bench-top Testing....................................................................................................... 35

11.2 Accumulator Case ............................................................................................................. 35

11.3 Drivetrain .......................................................................................................................... 36

11.4 Suspension ......................................................................................................................... 36

11.5 Aerodynamics .................................................................................................................... 36

12.0 Work Plan ............................................................................................................................. 36

12.1 Term 1-Work Plan and Status ........................................................................................... 36

12.2 Term 2-Work Plan and Vison ........................................................................................... 37

13.0 Budget ................................................................................................................................... 38

14.0 Appendix ............................................................................................................................... 39

14.1 FMEA ................................................................................................................................ 39

Works Cited .................................................................................................................................. 42

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List of Figures Figure 1: Accumulator Case ........................................................................................................... 8 Figure 2: Drivetrain Components ................................................................................................... 9 Figure 3: Rear Suspension Assembly ........................................................................................... 10 Figure 4: Sidepods ........................................................................................................................ 10 Figure 5: Rotating Motor Mount with Tensioning Rods .............................................................. 14 Figure 6: Outer Control Arm Components (Upper Left, Lower Right) ....................................... 15 Figure 7: Rear Rocker ................................................................................................................... 16 Figure 8: Battery Detail ................................................................................................................ 20 Figure 9: Safety Circuit Schematic ............................................................................................... 21 Figure 10: Front and Back of Accumulator Case ......................................................................... 22 Figure 11: Accumulator Case Side Impact and Rear Impact Safety Factors ................................ 22 Figure 12: Accumulator Case Vertical Load Impact Safety Factor .............................................. 23 Figure 13: Static Heat Transfer of Accumulator case ................................................................... 23 Figure 14: Motor Mounting Plate ................................................................................................. 24 Figure 15: Bearing Side Mounting Plate ...................................................................................... 25 Figure 16: Emrax 207 Torque and Power Curves ........................................................................ 25 Figure 17: Loads and results on motor side mounting plate ......................................................... 26 Figure 18: Loads and results on bearing side mounting plate ...................................................... 26 Figure 19: Loads and Results on Rear Rocker.............................................................................. 27 Figure 20: Rear Anti-Roll ............................................................................................................. 28 Figure 21: Total Deformation and Maximum Shear Strain .......................................................... 29 Figure 22: (a) Airflow Through and Around Sidepod (b) Airflow along Sidepod Curvature ...... 30 Figure 23: Airflow over Nosecone and Wheels ............................................................................ 31 Figure 24: Close View of Airflow Direction Under Nosecone and Around Front Wheel ........... 31 Figure 25: Airflow along Curvature Directed into the Chassis .................................................... 32 Figure 26: Flow through the Radiator ........................................................................................... 32 Figure 27: (a) Simulation Current vs. Time and (b) Current Draw in Failure Mode ................... 35 Figure 28: Project plan for the RREV2 ......................................................................................... 37

List of Tables Table 1: Objectives for the 2016 RREV2 ....................................................................................... 6 Table 2: Constraints for the 2016 RREV2 ...................................................................................... 7 Table 3 : Accumulator Case Material ........................................................................................... 12 Table 4 : Accumulator Case Design ............................................................................................. 13 Table 5: Motor Decision Matrix ................................................................................................... 13 Table 6: Gear ratio data ................................................................................................................. 14 Table 7: Anti-Roll Decision Matrix .............................................................................................. 16 Table 8: Sidepod design decision matrix ...................................................................................... 17 Table 9: Composite Material Decision ......................................................................................... 18 Table 10: Budget ........................................................................................................................... 38 Table 11: Cash Flow ..................................................................................................................... 38

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1.0 Introduction The Society of Automotive Engineers established Formula SAE in 1980. It began as a Baja competition with highly defined rules limiting innovation that could be done. Shortly after the competition was created, a new competition called Formula SAE was purposed to allow for a greater range of innovation among the students competing. Formula SAE is a fictional manufacturing company contracted to design small Formula-style racecar for the amateur racing market. Each team designs, builds, and tests a prototype based on a well-defined compilation of rules purposed both to ensure safety and to promote clever problem solving. The competitions provide teams the chance to demonstrate their abilities with respect to innovation, creativity and engineering knowledge when faced with real world problems and constraints.

Ram Racing was established in 1996 with the original Formula SAE competition, producing and competing with internal combustion cars. Currently, Ram Racing is headed by senior participating in senior design and supported by club members attending Colorado State University. Today’s Formula SAE club is made up of underclassmen from a variety of disciplines, with the majority being Mechanical and Electrical Engineering students. While the main goal of this club is producing a fully functioning vehicle for the 2016 Formula SAE competition in Lincoln, Nebraska, we are also very concerned with teaching the underclassmen good engineering practices and preparing them for a future iteration of our racecar.

During the competition, teams compete in three scored Static Events as well as four scored Dynamic Events. The Static Events include Design Judging, Cost Report, and Project Presentation, as well as a technical inspection that is not scored. The vehicle then competes in an Acceleration, Skid pad, Autocross, and Endurance events during the Dynamic portion of competition.

Ram Racing 2016 has elected to continue with FSAE Electric and build the EV2 car. Our senior design team is utilizing similar EV1 design concepts and lessons learned from last year to increase the performance and reliability of CSU’s electric Formula SAE racecar. Again, the senior design team is a joint project between the Electrical and Mechanical Departments at Colorado State University, which allows for better integration of electrical components and mechanical components.

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2.0 Problem Statement The primary goal of this year’s senior design team is to learn from last year’s difficulties and build the team’s first running electric vehicle for the Formula SAE competition. Due to budget constraints, the team has made the decision to move to a two year competition cycle. Going to competition is a very expensive endeavor and the team decided a better investment would be to save our resources and compete once we have a tested, reliable, and proven car. Additionally, moving to a two year design cycle will provide the team with much more testing time and allow for better battery data acquisition. The additional preparation will give the next team reliable data to begin the next design phase as well as an advantage heading into competition.

3.0 Objectives For the 2016 Ram Racing Electric vehicle (RREV2), the team is focused primarily on producing a tested and competitive car for Edays, as well as acquiring as much data as possible for next year’s team. Although we are not planning on competing this year, the car is still being designed to comply with all the FSAE rules. By designing the car as if we were going to competition, the data acquired will be more useful when designing next year’s car. This will give next year’s team a solid platform on which to build a competitive car for competition.

Table 1: Objectives for the 2016 RREV2

Objectives

Priority Rating

5-Highest 1-Lowest

Method of Measurement (Theoretical)

Method of Measurement (Actual)

Objective Direction Target

Car Mass 1 Model 4 Point Scale Decrease <600 lb Electrical Safety 5 Bench Test Field Test Pass Pass Tech

Packaging 3 Weight Distribution 4 Point Scale Maintain

45-55 Front-rear 50-50 Left-right

Technical Inspection 4.5 FSAE Rules Competition Inspection Pass Pass Tech

Auto Cross Time 2 Lap Sim Field Test/Data Log Decrease 55s (~avg. lap time) on FSAE

course Battery Removal/

Replace Time 4 Creo Model Field Test Decrease 30 minutes

Endurance Length 4 Lap Sim Field Test/Data Log Increase 25 km

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4.0 Constraints As stated above, the FSAE competition has a well-defined and very comprehensive set of rules to which all competition cars must comply. The rules restrict the design a significant amount as well as increase the challenge of the design in making sure the car adheres to these constraints. The following table outlines a few of the more important and challenging rules:

Table 2: Constraints for the 2016 RREV2

Ideally, the FSAE rules would be the primary driving factor behind design decisions, however, the short design cycle of less than one year introduces time constraints that must also be carefully considered and monitored to ensure the team is successful in executing their design.

The decision to reuse the chassis due to time limitations has been a strict constraint set by the team because it limits designs in various areas. However, reusing the old chassis allows for additional manufacturing, assembly, and test time. Furthermore, funding is a constraint unassociated with competition rules. The team is primarily self-funded, which limits some design decisions in an attempt to maintain a reasonable budget. The budget was constructed at the beginning of the design process to include all necessary components and reflects an amount the team believes is achievable. The total budget is outlined in Table 10.

Constraint Method of Measurement Limits Driving Factor

Wheelbase Length in inches >60in. FSAE Rule T2.3, pg 25

Track Width Width in inches >75% wheelbase

FSAE Rule T2.4, pg 25

Power Output Kilowatts <80kW FSAE Rule EV2.2

Accumulator Voltage Volts 300 V DC

Max FSAE Rule

EV1.1.2

Chassis Reused last year’s design Packaging Team decision

Suspension Inches of bounce and jounce 1in in both directions,

min

FSAE Rule T6.1

Funding Amount of money raised >$50,000 Budget

Time Days until E-days April of 2016 Senior design

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5.0 Design Summary 5.1 Electrical Currently, the electrical team is in the simulation and bench testing phase of the project. While the circuit simulation is completed on Simulink, parts are simultaneously being ordered for the benchtop tests of built circuits, which are to begin on December 7, 2015. The battery cells have been chosen and ordered along with the configuration in which they are to be placed. However, there are still a few minor decisions remaining for specific cell group connections.

5.2 Accumulator Case The accumulator case for this year is designed to contain 72 cells in series that will produce 295 Volts to the motor. To effectively supply this power, the battery cells must be cooled, preventing them from any damage. The cooling is accomplished by three large vents as well as cooling fins that disperse the heat away from the batteries. The sidepods are designed to supply enough airflow to effectively cool the batteries and prevent any possible heat related damage. The case is depicted in Figure 1.

Figure 1: Accumulator Case

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5.3 Drivetrain The drivetrain utilizes a new, lighter Emrax 207 motor coupled with a differential, having a 1:1 output ratio by means of a 530 motorcycle chain. The sprocket and differential are offset to improve motor packaging, using unequal length 4340 300M halfshafts to deliver the power to the 13 inch BBS wheels. Using a chain driven design allows gear ratios, ranging from1:1 to 4.5:1, to be changed during testing or competition in order to optimize motor efficiency for different track layouts. The full drivetrain assembly is shown in Figure 2.

Figure 2: Drivetrain Components

5.4 Suspension The suspension for the EV2 reuses the complete front and outer rear (uprights, brakes, spindles, etc.) from the RR13. The salvaged parts will simplify manufacturing as well as lower the cost of producing the EV2. The EV2 will be reusing the EV1 chassis, allowing the rear suspension to be updated. Fitting within the constraints of the rear chassis, the rear suspension points have been altered slightly, fixing major problems with the rear suspension of the EV1. The difficulties include a low ride height, no antiroll system, and too stiff of a rear suspension. The new rear points raise the ride height, while a new rocker is designed and an anti-roll bar is added. Suspension components are seen in Figure 3.

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Figure 3: Rear Suspension Assembly

5.5 Aerodynamics The aerodynamic package will consist of new sidepods and aero fabric. These components will increase the air flow to the batteries and cool a radiator, which in turn cools motor and high voltage controller (HVC). To create a successful electric Formula SAE car, it is imperative that the batteries are cooled to the optimum temperature, making sure battery damage does not occur. The creation of new sidepods and collaboration with the battery case will allow for maximum airflow to the batteries. Considering the main failure of last year, failure due to short circuiting in the battery case, it is even more important to analyze cooling of the batteries for the upcoming car. The success of the sidepod assembly will provide the team with a functional car and sufficient data to evaluate. The sidepods are displayed in Figure 4.

Figure 4: Sidepods

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6.0 Design Decisions 6.1 Electrical Over the course of the past semester, many design decisions were determined based on rules and cost. However, several other decisions were made based on weight, performance, and the implementation of a two year build cycle.

The safety and control circuits are designed primarily based on rules and requirements commissioned by the Formula SAE committee. The rules state only what the circuit must accomplish, not how to accomplish each task. This year, one of the goals is to have all safety circuits pass technical inspection, while remaining simple and reliable. Therefore, we designed the safety circuit primarily using relay logic; this system has been used in industry for many years and has proven to be very reliable. The relays in this circuit receive signals to the coils from other systems such as the Battery Management System (BMS), and Insulation Monitoring Device (IMD) causing the contacts either to open or close depending on the signal sent. This, in turn, will disrupt the safety circuit and cause the battery insulating contactors to open effectively, stopping the vehicle.

Battery configuration was also designed with reference to the rules, due to constraints in regards to monitoring the temperature and voltages of the batteries. For example, thirty percent of the battery cell temperatures must be monitored by the BMS and the thermistor sensors may not be more than 10mm from the negative terminal of the battery cell. There are more inputs into the decision of the battery design; Cost, size, recharge time, current demands for the motor, voltage characteristics, and BMS integration are all variables taken into consideration. The team first looked into off the shelf battery systems, focusing on other aspects of the car. However, the price of a pre-build battery system, for the application, is far too high. As a result, the team considered the successful and failing aspects of the battery from the previous year. The battery manufacturer (Melasta) of last year’s battery cell produced a very high power density battery with discharge and charge rates needed while staying within our budget. From this, we have continued to purchase from this company while choosing a battery cell which has larger tabs and slightly less mass. The decision to become a two year build cycle influenced the choice to make a smaller 72 cell accumulator with less capacity for the purpose of collecting data this year. The valuable data will lead to the use of re-generative breaking and a better cooling design for next year’s build.

The BMS system has also changed from the previous system. Last year’s challenge with connecting the BMS to the battery, while maintaining compliance with the rules was addressed. The thermistor used to measure cell temperature was placed directly on Elithion battery cell electronic boards, thus forcing the boards to touch the battery physically and increasing electrical shorts. This year we are using a system made by Orion, which features remote thermistors attached to the main controller via wires. This system is IP-65 rated and can withstand the rain tight regulation stated in the rules. The new system allows for a more uniform, organized, and professional featuring of the system to the battery cell while maintaining budget.

The choice of the Emrax 207 electric motor is based on weight, packaging, and performance. The motor has a peak torque comparable to that of an internal combustion Formula SAE vehicle, and couples well with the specs of the max battery voltage of 300 Volts mandated by the rules. This motor boasts up to 96 percent efficiency, water cooled, and is only 8 inches in diameter, with a depth of 3.3 inches, allowing for more systems to be implemented in years to come. The High Voltage Controller (HVC), produced by Rinehart, is the controller used to interface the

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synchronous electric motor and analog signals for speed. The team is using the controller because it can be programed to run multiple motor types and motor configurations. Also, this controller will not have to be bought as it is a carryover part from last year.

The choice to use an Atmel Real Time Micro Controller Unit (RMCU) device sprouted from the requirements of a system to analyze torque encoders and found its place in data acquisition. The rules state that more than one torque encoder is to be implemented and all encoders must have values within 10 percent of one another to elevate error detection and motor run away situations. This can be done with some clever circuitry but, we find it beneficial to use the RMCU because it can be used to monitor other systems as well. We have designed the RMCU so that the data coming from the motor controller, BMS, accelerometers, and speed sensors will be recorded so the car may be optimized in future iteration. With the donation of an Atmel AVR 32 bit development board this saved on budget.

6.2 Accumulator Case 6.2.1 Accumulator Case Material Type According to the FSAE rules, the accumulator case can only be constructed out of two materials, steel or aluminum. The battery case material was decided based on last year’s case. Previously, the case was constructed out of aluminum and the team ran into several problems trying to effectively weld the case together. Therefore, the team decided on using a steel case this year for easier welding and thinner material. The use of steel does not add substantial weight to the car. With the addition of a thinner steel, instead of aluminum, the weight of the case would only increase about nine pounds. A brief decision matrix is found in Table 3, below.

Table 3 : Accumulator Case Material

The steel case is the ideal choice for the design because it saves space and is the easiest material to manufacture and weld.

6.2.2 Accumulator Case Size This year, the team was left with minimal battery data and the need to determine the number of battery cells necessary to finish the endurance race at competition. The team weighed the options of either a 144 cell or 72 cell battery case. The 144 case would run half of the batteries in parallel, doubling the run time of the case. The 72 cell case is a much simpler design and saves space for other components in the back of the car. The team also decided to implement an air cooled case, rather than a water cooled design. The water cooled configuration would add significant complexity to the overall car design and would only be necessary if the car was running regenerative braking. A short map of the decision is shown in Table 4, below.

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Table 4 : Accumulator Case Design

The team decided to create a 72 cell, air cooled, battery case due to small size and minimal complexity. One of the main goals of this year’s car is to compile reliable and complete data for future Ram Racing teams. Additionally, the team will not be attending competition this year, so a large case for endurance was not deemed necessary. The case is designed to be adaptable to a water cooled case if the future team considers it essential for regenerative breaking.

6.3 Drivetrain 6.3.1 Motor Type/Model The main improvement to the drivetrain this year is the motor. A new, lighter motor will be used, ultimately providing a better overall fit for the car. A decision matrix is shown in Table 5.

Table 5: Motor Decision Matrix

The Emrax 207 motor proved to be best for our needs. The Yasa 400 motor has a similar power to weight ratio. However, at more than double the price and lack of availability, the Emrax 207 was determined to be a better choice.

6.3.2 Chain Adjustment An additional key design improvement is an improved process of tensioning the chain. Last year’s tensioner was inefficient for the torque output of the motor and was prone to loosening, allowing the chain to contain slack. The new motor was mounted in a way that it can be moved to adjust the tension in the chain. The unique mount eliminates the need for a dedicated chain tensioner. Due to the nature of an FSAE racecar and the frequency at which the driver accelerates and decelerates, the chain tension is very inconsistent. The inconsistent chain tension makes the force on a dedicated chain tensioner very inconsistent, which has a tendency to cause it to loosen or wear at an accelerated rate. By mounting the motor such that the distance between

Motor Value Rank Value Rank Value Rank Value Rank TotalYasa-400 52 2 360 1 90 1 $12,000 3 7Emrax 207 20 1 140 3 65 3 $5,000 1 8Remy 250 108 3 325 2 70 2 $7,000 2 9

Weight(lbs) Peak Torque(Nm) Peak Power(kW) Price($)

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the front and rear sprockets can be changed, the need for a separate chain tensioner is eliminated and the tension in the chain is be more constant.

Figure 5: Rotating Motor Mount with Tensioning Rods

6.3.3 Gear ratio In order to optimize the efficiency of the new motor, the car was analyzed in OptimumLap. Running the car on various tracks provides reliable data and also determines the ideal gear ratio to achieve both quick lap times and low energy consumption. The gear ratios are somewhat limited by packaging, with potential gear ratios ranging from 1:1 to 4.5:1. The data below, Table 6, shows this range of ratios run on a 70m drag strip to simulate the acceleration event as well as a 22km endurance track.

Table 6: Gear ratio data

As seen from the data, lap time and energy used are inversely effected by gear ratio. Due to the emphasis on testing, multiple rear sprockets will be manufactured for use during testing. The variety allows the team to see the actual effect of the gear ratio on energy consumption and lap time. In addition, other effects can be monitored, such as driver preference of location of torque curve in relation to car speed.

Final Drive Ratio [-] 1 1.5 2 2.5 3 3.5 4 4.5 1 1.5 2 2.5 3 3.5 4 4.5Lap time [s] 18.22 15.25 13.39 12.07 11.08 10.29 9.64 9.1 91.6 85.43 82.08 79.88 78.03 76.41 75.04 73.87Average Speed [km/h] 16.22 19.74 22.77 25.47 27.96 30.3 32.51 34.62 46.13 49.8 52.05 53.59 55 56.32 57.51 58.59Energy Spent per lap/run [kJ] 8.63 13.04 17.53 22.12 26.82 31.65 36.61 41.72 140.6 201.3 254.2 293 344.9 397.7 445.2 490.8Total Energy Spent [kJ] 34.52 52.16 70.12 88.48 107.3 126.6 146.4 166.9 2531 3623 4575 5275 6209 7159 8014 8834Top Speed [km/h] 55.02 68.21 79.9 90.8 101.3 111.6 121.8 127.9 55.02 68.21 79.9 90.8 101.3 111.6 121.8 127.9

70m drag 2012 Lincoln endurance

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6.4 Suspension 6.4.1 Suspension Points and Kinematics Inner suspension points were unable to be substantially moved, due to the restriction of reusing the EV1 chassis. The outer points in space, however, can be changed relatively easily, with only slight variations of the outer control arm components. The EV1 rear suspension caused a ride height that was too low and could not be easily raised without negative effects from the camber change. The new points on the EV2 raise the rear ride height 0.5 in from the EV1. The kinematic points on the rear rocker were also changed to more closely match the suspension travel as well as stiffness of the front suspension. All suspension had kinematic simulations ran using Optimum K.

6.4.2 Control Arm Components With the slight change in suspension points, the outer control arm ends require adjustment. The control arm ends follow the same design lineage of the past four cars developed by Ram Racing. This utilizes a pushrod configuration in the rear to help with packaging of drive components and shims for camber adjustment. These control arm ends also utilize the new machining technique used in the EV1, were the rod-end attachment slugs can be removed for easy replacement as well utilize in house machining. Components are shown in Figure 6.

Figure 6: Outer Control Arm Components (Upper Left, Lower Right)

6.4.3 Rocker Design The rear rockers were created using the points from Optimum K to maintain the best ratio to match the front suspension. With the optimum ratio, the rocker was designed to allow easy packaging of an anti-roll system that the EV1 did not include. The rocker was designed to be manufactured in two halves, mounted together as a single unit, utilizing the four mounting bolts to keep the entire part ridged when mounted.

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Figure 7: Rear Rocker

6.4.4 Anti-Roll Two options for the anti-roll are blade style and box style. The blade style uses a blade that can be rotated to adjust the bending moment, altering the stiffness of the anti-roll bar. The box style uses multiple holes that change the moment arm length top to adjust the stiffness of the anti-roll bar. To determine the anti-roll style a weighted decision matrix was used, Figure 7Table 7.

Table 7: Anti-Roll Decision Matrix

6.5 Aerodynamics Another main change to the aerodynamics of the car is the airflow system. The improved system provides cooling air to the battery case and radiator. With increased air intake abilities, the sidepods bring the maximum amount of air to the battery case. One sidepod also is used to hold a

Blade BoxEase of

Adjustment2 0 0

Amount of Adjustment

2 1 -1

Ease of Manufacturing

5 -1 1

Simplicity of Design

4 -1 1

Weighted Total

-7 7

Style (-1,0,1)Catagories Weights (1-5)

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radiator, used to cool the water flowing to the motor and HVC. With increased curvature and a tight fit to the car, air swirls from the sidepod directly to the three air channels in the battery case, cooling the batteries. Aero fabric will be utilized on the chassis tubes to bounce air back into the sidepods where it will then be rerouted to the battery case.

6.5.1 Sidepod Decision The main goal of the sidepod design process is delivering as much air as possible to the battery case. The optimization process was performed in several steps, tuning both the inlet and outlet of the cooling duct to the suit the exterior flow field. This helped create the four main designs, which were then analyzed in fluent. The Pugh matrix shown below, Table 8, illustrates the considered designs as well as the result. As seen in the matrix, the determined solution is determined to be the large air intake opening and curvature option. With the large intake, the air can be rerouted with enough turbulence to follow the curvature of the sidepod into the chassis. Once the cool air reaches the battery case vents, it will cool the batteries to an optimum temperature and protect them from damaging temperature of 60C. The curvature of the sidepod was then created in Creo and analyzed in fluent.

Table 8: Sidepod design decision matrix

6.5.2 Composite Material Decision Since the sidepod is made from consumable material, it is not meant to hold up in a crash. Instead, it completes its function in maximum racing conditions. The target material is fiberglass because of low cost, high tensile strength, high fatigue resistance, and high compression strength. This setup will allow for some flexibility in the sidepods and ensure that they will not break under racing conditions. The Pugh matrix, Table 9, shown below, illustrates the most important materials for design. Fiberglass offers enough flexibility and compression strength to allow air to flow through the inlet with very little deformation in the sidepod. This also helps with the fatigue resistance of the sidepod, since very little deformation occurs it allows for a very long sidepod life.

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Table 9: Composite Material Decision

7.0 At-risk Items and Mitigation Plan 7.1 Funding Formula SAE is a self-funded club aside from the initial fund provided by the Mechanical Engineering Department for the senior design project portion. The initial funding can empty quickly with the cost of competition registration, expensive electrical items, chassis manufacturing, and machining.

7.1.1 Competition Registration cost for Formula SAE Electric Lincoln is $2200. The team set a deadline to raise $5000 to cover the registration fee as well as have a good monetary start to purchase large budget parts needed to compete. Since this deadline was not reached, the team will not be competing in the 2016 competition. The alternative to competing will be in depth testing of electrical and mechanical systems to provide data for the RREV3 car next year. One criteria set for not competing is the full completion and the start of the testing cycle by E-Days.

7.1.2 Motor and BMS The motor and BMS cost a combined $7000. A majority of the cost is from the $5000 EMRAX motor. If we are unable to procure the necessary funds to purchase the new motor last year’s Remy motor will be retrofitted and mounted if we are not competing. This will still allow for a drivable car that data can be pulled from. There is no alternative for the $2000 BMS. The BMS is needed to run the car as well as charge the complete battery pack. Last year’s BMS is unusable due to a catastrophic short that occurred during testing last summer.

7.1.3 Chassis Manufacturing and Machining Stock The chassis from the RREV1 is being reused and retrofitted with different mounting tabs. This frees up the $3000 needed to cope and bend all the chassis tubes. A majority of the machining stock in the past was donated by Woodward and we hope that this will continue this year. If not a plan is in place to reuse parts that are already manufactured.

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7.2 Manufacturing Capabilities The most complicated manufacturing is associated with the suspension and battery. The complexity of the suspension comes from the unique geometry and packaging requirements. The battery complications are mainly rules and safety based.

7.2.1 Suspension The very complicated parts such as the uprights will be reused from the RR13 vehicle. The lower outer control arm of the rear suspension used to require an advanced CNC provided by Woodward. Last year a manufacturing plan was created for these control arm components that allowed the entire part to be manufactured using the standard CNC’s available in house. This simplifies the manufacturing capabilities and allows us to utilize team manufacturing time instead of relying on outside sources.

7.2.2 Battery The battery is a challenge because of the requirements given by the rules and because power cannot be turn off at the battery cell. The most challenging rule is as follows, there must be at least thirty percent of battery cell temperatures monitored at all times with the thermistor less than 10mm from the negative cell. This creates a circuit board mounting problem for the BMS, however we have found a BMS system which allows us to mount the temperature senor off the board and directly on the battery cell. This BMS along with the development of a clamp style connection on a custom battery wiring harness will ease the manufacturing process of the battery and allow the battery to be built in house.

7.3 Sidepod The biggest modes of failure for this year’s sidepods will be failure to cool the batteries and detachment from the chassis. If the sidepods are unable to reroute enough air to the battery case or detach from the car; major damage can occur. If the battery case is not properly cooled and temperatures reach above 60C it could cause permanent battery damage. To protect against this analysis of the sidepods airflow will be done in fluent and a wind tunnel will be utilized with 3-D printed sidepod and battery case models to validate fluent results. If the sidepods were able to detach from the vehicle it could prompt the batteries to overheat and cause irreparable damage or permanently damage the sidepod upon ground impact. To prevent this from occurring, each sidepod will be mounted to the chassis at four distinct points using two quarter turn fasteners on top of the sidepod and two tabs going through the bottom of the sidepod to hold it in place. This will keep the sidepod fixed in place and significantly decrease the chances of detachment from the chassis.

8.0 Final Concepts 8.1 Electrical The high voltage Controller is manufactured by Rinehart Motion Systems, is the PM100-DX model which can take in input power of up to 400 VDC and produce an output of up to 350Vrms AC. For this application, the team will not exceed 300 VDC with an output current of 300 amps. This system takes the DC input and produce a Sine wave or AC signal using DC to AC conversion. The method used to convert the DC to AC is via MCU control and IGBT (Insulated

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Gate Bipolar Transistor) device. This MCU is powered by a low side battery in the range of 8V – 18V and is capable of other function such as CAN communication and can take inputs from the accelerator pedal (Via MCU signal voting algorithm).

The motor chosen is the EMRAX 207 (208 depending on manufacture year), produced by ENSROJ manufactured in Slovenia. The motor can produce 73 ft-lbs of torque when supplied 150 Amps. The motor will be attached to the drive axil using a chain and sprockets as described in the drivetrain section. In future iteration the motor can be daisy chained to produce double the torque or set on each axil to supply higher traction with double the power output. The model chosen will be water cooled and has a resolver in the motor to tell the controller where the rotor is positioned for a more efficient use of power.

Melasta is the manufacturer of the model SLPB9664155, Lithium Cobalt Ion batteries chosen. The prismatic cells and are capable of a 15C discharge rate at 150 Amps continuous and 200 Amps peak. For this reason, the battery cells are paired perfectly for the motor, as the power curve of the motor begins to come into saturation or flatten outs at 200 Amps. The battery cells will be connected in series of 72 to produce a voltage of 295.2 V and 266 V nominal see Figure 8.

Due to the lithium ion chemistry, the batteries must be monitored and kept within a voltage window of 4.2 V to 3.0 V to keep from battery destruction. Previously stated, the BMS was chosen, produced by Orion and will be the 108 cell enclosure with the Thermistor Expansion Module. This system is CAN capable from which the RMCU can collect data.

Figure 8: Battery Detail

According to the rules there is very little that can be controlled with the RMCU. However, there are system such as the encoder checks that may be performed on the RMCU and many other applications that can be monitored and recorded. Atmel is a manufacturer of semiconductor product, and have a line of automotive grade MCU chips along with development boards to use

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as prototype tools. Atmel has donated one of their best RMCU chips already attached to the board for our convenience. This board is capable of analog to digital conversion, digital to analog conversions, CAN communications, audio in and out, local network interfacing, GPIOs (general purpose input outputs) and pulse width modulation. The team has implemented this into the design to monitor and record many of the operations being performed on the car, acceleration, forces acting on the car, to perform brake plausibility checks, and accelerator encoder checks. This information will then be saved for future steps to optimize the cars performance, sent onto the HVC for acceleration, or dashboard to display status of the vehicle.

The Formula SAE rules specify a Bender, A-Isometer to be used for monitoring the potential insulation between the high voltage and low voltage systems. The system uses the IR 155-3203 model from last year’s design.

All these main components interact with the master safety circuit (MSC) to shut off the accumulator power to the tractive system in the event there is a fault in any system see Figure 9. The MSC has three emergency-stop switches, one in the cockpit compartment and one on either side of the vehicle for manual shut off. Both the high voltage and low voltage systems have master switches and for added safety the high voltage has an easy disconnect immediately after the accumulator plugs. In the event there is a crash the Formula SAE rules specifies a specific mechanical resetting crash senor (Sensate) to be used and incorporated into the MSC.

Figure 9: Safety Circuit Schematic

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8.2 Accumulator Case The initial problem for the accumulator case was finding a way to cool the batteries as well as having a water tight case. The problem was solved by having large cooling vents in the back of the case to make sure efficient air flow will pass through the case. The case aslo includes several heat sink fins that seperate the batteries and direct the heat from the batteries to the cooling vents. The battery case has to be small enough to fit behind the driver seat so the side pods could cool the case and prevent the batteries from heating damage.

Figure 10: Front and Back of Accumulator Case

Figure 10, above, shows the final designs of the case including the 72 battery cells that will make up the battery pack. The top part of the case is used to hold the high voltage fuses and relays.

Figure 11: Accumulator Case Side Impact and Rear Impact Safety Factors

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Figure 12: Accumulator Case Vertical Load Impact Safety Factor

Figure 11 and Figure 12 show the safety factor of the battery case after the allowable load is applied. According to FSAE rules, the battery case must withstand a load of 40g (1100lbf) in the longitudinal direction and the lateral direction. The forces and safety factor of the longitudinal and lateral directions are shown in Figure 11. The rules also state that the battery case has to be able to withstand a vertical load of 20g (550lbf). Figure 12 resembles the analysis of a vertical load on the battery case. The case is designed to be structurally sound and will be able to withstand the loads required by the FSAE rules committee.

Figure 13: Static Heat Transfer of Accumulator case

Figure 13 models the heat transfer of the accumulator case when there is no air flow going through the batteries and the cells are only being cooled by the outside air. It is essential that the batteries stay below a temperature of 140℉. If they exceed this temperature the batteries could

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be permanently damaged. The air flow that will be provided by the side pods should be more than enough to keep the batteries cool enough to stay away from damaging temperatures.

8.3 Drivetrain The main design problem with the RREV2 drivetrain was mounting the unique Emrax 207 motor. The motor is unique because the outer casing of the motor spins. This means the motor must be mounted to a single plate on the back of the motor and a shaft support on the front, rather than multiple mounting points on the sides of the motor.

Figure 14: Motor Mounting Plate

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Figure 15: Bearing Side Mounting Plate

Figure 14 shows the mounting plate on the back side of the motor. The plate will be waterjet cut from ½ inch 6061 aluminum and mounts to the motor using 6 M8 bolts. The other side of the motor is supported by a sealed roller bearing on the ¾ steel shaft as seen in Figure 15. These two plates are mounted to the frame via tabs welded directly to the frame. In order to simplify the chain tensioning system, this entire assembly will rotate about the bottom mounting holes (a) to tighten the chain. To achieve this, the front lower mounting holes (b), are slotted and the upper holes (c) are attached via threaded rods.

Figure 16: Emrax 207 Torque and Power Curves

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Analysis was done on the plates using FEA (Finite Element Analysis). The Emrax 207 motor produces 140 Nm (103 ft-lbs) of torque (Figure 16). Figure 17 shows the motor side plate loaded with the appropriate torque loads on each of the six holes as well as the force from the tension in the chain. This final design of the plate yields a Safety Factor around 8.61.

Figure 17: Loads and results on motor side mounting plate

Figure 18 shows the bearing load applied to the bearing side mounting plate. The plate has a safety factor of 8.34.

Figure 18: Loads and results on bearing side mounting plate

A keyed #50 sprocket will be used to drive the 530 motorcycle chain and transmit the power to the rear wheels. The sprocket used will be purchased from surplus center and will use key and keyway sizing according to specifications which exceed the tensile strength of the 530 motorcycle chain used (9700lbs).

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The chain, rear sprocket, deferential, CV joints, half shafts, and hubs are being reused from the RREV1 which utilized a motor with higher peak torque so no analysis was done on these components.

8.4 Suspension The suspension on this year’s EV2 will consist of the full front suspension and outer rear suspension from the RR13 car. This restricts the front to a pull-rod configuration and the rear to a push-rod system. The reuse of the EV1 chassis restricts design, though the major problems have been addressed. The ride height has been increased by 0.5 inches and the upper control arm chassis points have been lowered by 0.25 inches. The EV1 also had a problem with the rear suspension being extremely stiff and has been addressed with a redesign of the rear rocker. To match the motion ratios of the front and the rocker, tabs will be fixture to ensure the system is in plane.

The outer control arm components (Figure 6) will be produced in three parts, two rod connections and the main body. This allows the parts to be manufactured in house and allows for an inexpensive replacement of control arms when damaged. The parts will be made from aluminum billet and round stock.

The rocker (Figure 7) will be manufactured in two halves then mounted together to form the full rocker. The rockers will also be manufactured in house using aluminum billet.

Figure 19: Loads and Results on Rear Rocker

The 600lb load was determined using the approximate 1.5 inch of damper travel expected with three degrees of body roll of the car and an estimated spring stiffness of 400 lb/in. This allows for some wiggle room, as this is the stiffest spring available for the dampers ran and 300-350 lb/in springs are used on the rear of the previous FSAE cars.

The anti-roll will be a box style adjustable system made from steel. The adjustment comes from multiple holes allowing for a variable moment arm length. The arms will be welded to a steel torsion rod and mounted using aluminum mounting blocks and brass bushings.

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Figure 20: Rear Anti-Roll

8.5 Aerodynamics The failure of last year’s car was caused by a short circuit in the batteries, which fried the BMS and caused the car to be unusable. To fix that problem the team will be forcing a maximum amount of air across the battery case to significantly reduce the chance of battery damage. A first step in the process was to improve the aerodynamic shape of the racecar in the vicinity of the cooling air inlets. To ensure battery damage does not occur they will need to be cooled below 60C at all times. This year’s sidepods will be validated with ANSYS to determine the stresses and deformation of the sidepod at max speeds and forces of a Formula SAE car. Fluent will also be utilized to show airflow through the sidepod and validate that it will be going directly to the battery case. 3-D printed models of the sidepod and battery case will also be put into a wind tunnel and analyzed to verify where the airflow will be directed.

8.5.1 Meshing Analysis To create accurate force analysis in ANSYS and airflow in fluent the meshing must be correct or the results will be skewed. The team used different meshing schemes for the three different scenarios that were analyzed. The first model used was for stress and deformation analysis of the sidepods at maximum racing conditions. The next condition analyzed was airflow routing in fluent and a finer mesh was needed to observe better results. Finally a symmetrical bluff body model of the chassis and sidepod was created to analyze the turbulence through the sidepod and to analyze what occurs when aero mesh is applied to the chassis tubes to assure maximum airflow to the battery case. All three models utilized hex dominant meshing on the sidepod to assure that brick meshing was utilized in ANSYS. Brick meshing was desired since it is the best option for thin 3-D models since the sidepod will only be .3 in thick and made from fiberglass.

8.5.2 Stress Analysis The sidepods are a consumable product and are therefore meant to hold up under racing conditions and not a crash. In ANSYS the design was put through 2 G’s of force on the front to simulate maximum racing conditions with wind speeds and sharp cornering of the vehicle. The

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sidepods will be fixed to the chassis at four distinct points to prevent movement and detachment from the racecar. Since fiberglass is being utilized in the fabrication of the sidepods, it is important to analyze the deformation and strain since the stress analysis of a composite is very hard to calculate, unless all material properties are known. They also heavily depends on the directionality of the fibers that are laid out and are not known until fabrication. For this reason the safety factor analyzed in ANSYS is purely theoretical and the integrity of the sidepod will be determined by the deformation and maximum shear strain put on it with 2 G’s of force. The strain energy may be used as a fatigue failure criterion for different composite materials. The area under the stress strain graph is the strain energy per unit volume. The goal is to build a sidepod out of a composite material that will deflect minutely and not break under racing conditions. The target material is fiberglass because of its material properties and how it deforms under compression and tensile forces. This setup will allow for some flexibility in the sidepods and ensure that it will not break under racing conditions.

As seen below in Figure 21 the max deformation of the material will occur on the left side of the sidepod, which has the thinnest wall so that a maximum amount of air can be brought to the battery case. The maximum deformation that will occur is 1.56e-4 in, which is due to the high stiffness and compressive strength of the composite and will have no problems with brittle fracture. Figure 21 above also shows the maximum shear strain on the sidepod, which is 3.51e-5 in/in. This is acting on the air intake flap and is due to air being forced into the curvature of the sidepod. This is a very minimal strain and will not cause brittle fracture on the sidepod because of the composites compression and tensile strength.

Figure 21: Total Deformation and Maximum Shear Strain

8.5.3 Airflow Analysis Two different models will be analyzed in fluent to verify the airflow. The first is just a sidepod to show the maximum amount of air entering through the inlet and how it will exit with the chosen curvature. The second model is a symmetry bluff body of the chassis with the sidepod fixed in place to show the air swirl as it is redirected off the aero mesh and back into the sidepod where it exits into the chassis headed towards the battery case.

Fluent was first utilized in the design process to determine which sidepod design would bring in the most air. The decision process was then refined further by showing the flow path through the

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sidepod and where it would exit into the chassis. This data was then put into a Pugh matrix to determine the final sidepod design as shown in Figure 4.

When analyzing the sidepod design it was also important to consider the cooling of the radiator, which will be placed in one of the sidepods. A sidepod with a big inlet and sufficient airflow is imperative when cooling a radiator. The heat rejection of a radiator is a function of velocity across the radiator core and a semi-empirical relation is given by the Petukhov and Popov correlation:

𝑁𝑁𝑁𝑁 = .023 𝑅𝑅𝑒𝑒𝑛𝑛 ∗ Pr ̂ .4

It can be seen that in order to achieve the highest heat rejection at the lowest possible drag the velocity distribution at the front face of the radiator must be uniform. Therefore, the purpose of the sidepod curvature is to ensure an even velocity distribution at the front face of the radiator and also balance the pressure distribution at the inlet and outlet such that the lowest overall drag can be achieved while maintaining a sufficient flux. The ideal shape and size of the inlet is based on the flow in front of the duct with considerations on the pressure needed to drive the flow through the radiator.

To make the simulation and optimization as realistic as possible a fully detailed CAD symmetry geometry of the car was used. The complete hexahedral core meshing contains 1.8 million elements to fully analyze the flow around the car (Figure 22). The airflow to the car was solved using fluent 16.2 and a realizable k-epsilon model with second order discretization schemes for momentum, kinetic energy and dissipation rate. A k-epsilon model was used because it is proven to give accurate results in road vehicle aerodynamics applications. A virtual wind tunnel was used to simulate a free stream velocity of 60 mph with the car going straight. Velocity inlet condition was used at the inlet and a pressure outlet condition was used for the exit of the tunnel. Stable body forces and mass flow rate were used through the sidepod inlet.

Figure 22: (a) Airflow Through and Around Sidepod (b) Airflow along Sidepod Curvature

Figure 22a) depicts airflow through and around the curvature of the sidepod using velocity vectors to show direction. It is important to note that the air velocity will increase along the inlet curvature causing a pressure drop and therefore more air is drawn into the sidepod. Figure 22b) shows the reaction of the airflow along the curvature. It is important that the air is sloping downward along the curvature and exiting the bottom left. This is good because the air will need to slope downward into the chassis in order to be vented directly towards the low mounted battery case.

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Figure 23: Airflow over Nosecone and Wheels

Figure 23 and Figure 24 display the movement of air along the curvature of the nosecone and wheels utilizing arrow vectors to display direction. The air will not only flow underneath the nosecone but also around the front wheel and will be directed towards the sidepod. This allows a maximum amount of air to be funneled through the sidepod curvature and towards the battery case.

Figure 24: Close View of Airflow Direction Under Nosecone and Around Front Wheel

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Figure 25: Airflow along Curvature Directed into the Chassis

Figure 25 displays the direction of the airflow along the curvature of the sidepod. This is important because it shows where the air will enter the chassis and eventually reach the battery case. The vectors show a sloping motion down and to the right, which is consistent with the flow through the sidepod as shown in Figure 22a).

Figure 26: Flow through the Radiator

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Figure 26 utilizes a velocity path line to provide an image of the flow around the sidepod and also through the radiator. The airflow speeds up as it reaches the inlet curvature of the sidepod and immediately slows down once it enters the radiator creating a swirl of air. Providing extra space between the radiator and sidepod wall increases the mass flow rate and decreases the backpressure caused by the radiator. The radiator is angled at 70 degrees to increase the pressure on the radiator face. By angling the core, the effective cross sectional area that air travels through is dramatically increases, thus reducing the airspeed through the radiator and increasing the cooling capabilities.

9.0 FMEA The FMEA analysis is used to evaluate each major component by the risks or failures it may have. After each component was identified and failure points were determined, the team elaborated on each failure, assigning the consequence a system of rank to govern the severity and likelihood of occurrence. In addition, the team prepared a mitigation plan for each area of the various components to determine how the problems will be solved.

The major mechanical FMEA components were the control arm, rocker, drivetrain, sidepod, as well as many electrical additions, BMS, IMD, RMCU, HVC, MSC, ACC, and motor. In general, failures focused on performance and safety precautions. The mitigation plans were largely aimed at remaking failed parts or replacing pieces as necessary. Details of FMEA can be found in14.0 Appendix.

10.0 Design for X 10.1 Cost The team is very limited by cost and overall funding. Though the team received some funding from the school, it is a minimal amount compared to the total cost of the project. With the design of each component, cost was a focus point. Manufactured parts were cost conservative, but some electrical and main components are simply expensive. One severe example of the design for X, cost focus, is the decision to extend the build time to two years. This decision, though it included many factors, was largely cost based. The team decided to save money by moving to a two year cycle.

10.2 Competition Though the team is not attending competition this year, most designs are still going to be a part of the future competition car, due for completion next year. Due to the compounding design cycle, the competition rules are still a large factor in completion of the project. The objectives and constraints are largely based on these principles. Many of the electrical components as well as details of the other designs are drawn from competition rules.

10.3 Data Collection Above all else, the main purpose of the testing this year is to get reliable and complete data for next year’s design team. Due to the lack of information for the previous electric car, the team has overcome many hurdles in an attempt to compensate for the gap. To advance next year’s design,

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the team aims to compile data, mainly for batteries. The testing of the car has been thoroughly planned and heavily weighted in the scheduling and design processes to achieve this goal.

10.4 Manufacturability In addition to other design goals, the team plans to design for manufacturability. Though some pieces are being sent out for manufacture, several are being produced in house. An example of this design for manufacturability principle is in the battery case. Previously, the team had run into several problems with welding when using an aluminum case. To compensate, the team has changed the design and chosen an easily wieldable material, steel. More than being aware of manufacture processes, the team has chosen common, reliable materials to also save time and cost of manufacture.

11.0 Validation 11.1 Electrical 11.1.1 Simulation For prototype evaluation of the electrical components, simulation of electrical systems is accomplished via Simulink with bench-top testing of physical circuits for physical confirmation of functionality. Bench-top circuit tests are scheduled to begin December 7 and continue through winter break. If problems in the circuit are present, redesign around new components and schematics in consultation with team electrical safety advisors will be conducted.

Utilizing time-delayed closing of safety switches and subsystem activation times, Simulink demonstrates the expected behavior of the system per initial design considerations. The LV Battery demonstrates an expected current draw of approximately 4 Amps, with a voltage drop of .001 Volts, as both safety switches and subsystems are activated. Figure 27a clearly shows the classic stepped response of current draw as subsequent systems activate. While Figure 27b shows the step response under failure conditions. As subsystems turn on the current draw steps up and when a failure is detected the system shuts down and current draws are stepped down as the subsystem shuts off. Not demonstrated here is the HV system, which has proven very difficult to model due to lack of knowledge including HV control parameters, motor dynamics, and pre-charge/discharge circuitry, without physical testing; most parameters provided by the vendor are not sufficient to get a detailed account of system behavior. In addition to the lack of physical parameters, modeling of any system cannot take into account the real-world physics of electrical components: variation of windings of inductive cores for relays, battery noise, parasitic capacitance of inductor cores for motor, relay, and subsystem components, temperature effects, subsystem time-dependent behaviors, switch bounce, as well as a myriad of other facets cannot be modeled effectively.

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Figure 27: (a) Simulation Current vs. Time and (b) Current Draw in Failure Mode

11.1.2 Bench-top Testing With the limited nature of modeling accuracy, bench-top testing becomes paramount to effective electrical system design. Through bench-top building of the real-world circuit, we can effectively step through each scenario that can be expected and check the response of the system against the system requirements.

To begin bench-top testing, each subsystem is wired individually and tested while monitored by oscilloscopes and multi-meters. The subsystems will then be given all expected inputs for both failure and normal operation. Once the desired outputs have been achieved for each subsystem the systems are interconnected into the respective electrical systems of the low voltage and high voltage systems independently, and tested to reveal the system outputs. These low and high systems are tested until they consistently produce the appropriate output response for each input. After the low and high voltage systems show appropriate responses they will be interconnected and run through the tests again. At the end of each test-run in each phase (sub system and interconnected systems) the circuit will be evaluated and modified as needed to achieve the response required from the over-all system. Performing these tests in phases will reduce any necessary redesign time as problems reveal themselves more easily and frequently with incremental testing.

11.2 Accumulator Case Structural validation for the accumulator case is not easily done without building multiple cases and the fixturing necessary to impart the maximum force on them. The case is designed to withstand a force of 40g’s, this would only happen if another formula driver crashed into the back of the car during the endurance race. The accumulator case is also fully protected by the structure of the chassis and a force that large on the case is highly unlikely.

The air flow though the accumulator case will be validated by 3D printing the accumulator case as well as the side pods that direct the flow into the case. The 3D printed compensates will be

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placed in a wind tunnel with a smoke machine in order to visualize the flow through the side pods. This will ensure that the accumulator case is getting the proper amount of air flow to effectively cool the battery cells.

11.3 Drivetrain Validation for the drivetrain will primarily be done during testing in March. Testing outside of the car was decided against due to lack of funding and time. The components in the drivetrain that were designed all have a relatively large Safety Factor and the components that were purchased all have torque/load ratings that are accurate and well above what is needed.

Failure of any of the drivetrain components should be fairly detectable (cracking or deformation) and in the event of a full failure the consequences are small being only an inoperable car or in an extreme case minor damage to other components.

11.4 Suspension Like the drivetrain, the suspension components will be primarily tested while testing and tuning the completed car. Tensile pull tests will be performed on sacrificial carbon tubes with bonded rod ends, this will test and verify bond gap and epoxy bond strength.

11.5 Aerodynamics To validate all fluent calculations and air flow analysis 3D printed models of the sidepods and battery case were made and will be put into a wind tunnel and analyzed. These 3D printed models will be a scaled down version of the actual part and the airflow will be analyzed in the wind tunnel to prove they are completing their task. The sidepods are meant to bring the maximum amount of air to the battery cases air channels and therefore cooling the batteries. We will be using a grey smoke to show that the air will flow around the wheels and into the sidepods, which will reroute the air to the battery case.

12.0 Work Plan 12.1 Term 1-Work Plan and Status Overall the project is on track with the exception of bench testing and battery case manufacturing. The team reserved enough cushion time over winter break to be able to get back on schedule. The rolling chassis will be completed by the end of break as well as a manufactured battery case. Extensive benchtop testing will take place on the electrical components to ensure all components are tested and ready to be placed into the car. The main factors in falling slightly behind have been budget and electrical oversight. By changing the project to a two-year design cycle for competition, we were able to reallocate some funding to get back on track with purchasing components. Three ESA’s (Electrical Safety Advisor) were also obtained to help oversee benchtop testing and circuit assembly.

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Figure 28: Project plan for the RREV2

12.2 Term 2-Work Plan and Vison The biggest hurdle for nest semester will again be funding. The Orion battery management system is the next large money purchase the team will make when more funding is available and will be incorporated into the battery assembly. With the accumulator assembled the BMS can then be bench top tested with the already benchtop tested safety circuits. The motor will be ordered after the BMS when more funds have been accumulated and will be tested with the remaining systems in the car. Once all components have been purchased and tested with the system we will then integrate all subsystems into the vehicle frame.

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13.0 Budget This year’s budget is based off of rebuilding all of the electrical components of the car. The

budget is much larger than expected due to the team having to purchase new batteries and a new BMS. Fortunately, the team does not have to weld a new chassis so that saves on some of the

expenses.

Table 11 demonstrates the cash flow from sponsors as well as the large components that have been purchased by the team thus far. The table shows how much money we still need to raise in order to have the base components for the car. In order to reach this goal, the club has a business team that are contacting potential sponsors.

Table 10: Budget

Table 11: Cash Flow

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14.0 Appendix 14.1 FMEA

Battery Management System

Formula = (Rank/40)*R.O.D.*

D

Function Performance StandardsFunctional

Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40)Rate of

OccurrenceDetectibilit

y

Risk Ranking(1 = Lowest; 100 =

Highest)

Normalized Rank (1= high, 0 = low) Mitigation / Redesign Plan

BMS Controller Damaged Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Battery Cell(s) non-functional

Battery cells explode/catch fire OR BMS has unclearible erroor,

BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable 0 (E), 2 (S), 10 (O), 4 (NO) 5 1 0.40 0.0889

Microboards on cells Damaged Battery cells explode/catch fire

Vehicle Non-Functional, ACC Unusable 0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

BMS Controller Damaged Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Battery Cell(s) non-functional

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 6 1 0.40 0.0889

Microboards on cells Damaged

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Disconnect Accumulator from LiPO Charger if charge current

exceeds rate of Z A

Charger Does Not Disconnect

BMS Controller/Current Sense Damaged

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

BMS Controller Damaged Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Charger/HVC Does Not Disconnect

BMS Controller/Temperature

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Battery Cell(s) Over-temperature from

Charge/Use

BMS turns off, BMS Failure Indicator Light

Vechicle Shuts down for cool down period

0 (E), 2 (S), 2 (O), 2 (NO) 9 1 1.35 0.3000

IMS Trips Due to Short of HV to LV system, IMS Failure

Vechicle Shuts down until Error is Corrected

0 (E), 2 (S), 2 (O), 2 (NO) 1 1 0.15 0.0333

Battery cells explode/catch fireVehicle Non-Functional, ACC

Unusable 0 (E), 2 (S), 10 (O), 4 (NO) 1 1 0.40 0.0889

Monitor Temperature of 4.2 V LiPO cell

(Primary)

Disconnect Accumulator from LiPO Charger/HVC if

temperature of 30% of cells exceed 60⁰C

HVC Does Not Disconnect

Validate inter-cell connection of 4.2 V LiPO cells via TAP

(Primary)

Validate series/parallel connection of cells to prevent damage main BMS Controller

TAP Gives False Validation TAP/BMS Damaged

Monitor State of Voltage of 4.2 V LiPO

cell (Primary)

Disconnect Accumulator from LiPO Charger if X% of

accumulator cells exceeds 4.2 V

Charger Does Not Disconnect

Balance Y cells to equal Voltage Cell(s) Do Not Balance

Monitor Current Output of 4.2 V LiPO

cell(s)(Primary) Disconnect Accumulator from HVC if operating current

exceeds Z A for T seconds

HVC Does Not Disconnect

Monitor State of Charge of 4.2 V LiPO

cell (Primary)

Disconnect Accumulator from LiPO Charger if accumulator exceeds 300 VDC (Nominal)

Charger Does Not Disconnect

Balance Y cells to equal Charge Cell(s) Do Not

Balance

IMD Formula = (Rank/40)*R.O.D.* D

Failure Modes Failure Effects Consequence Category Rank (Total out of 40)Rate of

Occurrence

Detectibility

Risk Ranking(1 = Lowest; 100 = Highest)

Normalized Rank (1= high, 0 = low) Mitigation / Redesign Plan

AIR Fails to Open Battery cells explode/catch fire, IMD Failure Indicator Light, Electric Shock

Vehicle Non-Functional, ACC Unusable , Injured Personel

2 (E), 2 (S), 10 (O), 2 (NO)

2 1 0.80 0.1778

IMD Damaged Battery cells explode/catch fire, IMD Failure Indicator Light, Electric Shock

Vehicle Non-Functional, ACC Unusable , Injured Personel

2 (E), 2 (S), 10 (O), 2 (NO)

2 1 0.80 0.1778

AIR Fails to Open Battery cells explode/catch fire, IMD Failure Indicator Light, Electric Shock

Vehicle Non-Functional, ACC Unusable , Injured Personel

2 (E), 2 (S), 10 (O), 2 (NO)

2 1 0.80 0.1778

IMD DamagedBattery cells explode/catch fire, IMD

Failure Indicator Light, Electric ShockVehicle Non-Functional, ACC

Unusable , Injured Personel2 (E), 2 (S), 10 (O), 2

(NO) 2 1 0.80 0.1778

Real-time MicroController

Formula = (Rank/40)*R.O.D.* D

Function Performance Standards

Functional Failures

Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurrence

Detectibility

Risk Ranking(1 = Lowest; 100 = Highest)

Normalized Rank (1= high, 0 = low)

Mitigation / Redesign Plan

Data Sent to RMCU but Not Received

Data not recovered Data Not Recovered 1 (E), 1 (S), 2 (O), 1 (NO)

1 3 0.38 0.0833

Data Sent and Received by RMCU but improperly handled

Battery cells explode/catch fire

Data Not Recovered 1 (E), 1 (S), 2 (O), 1 (NO)

1 3 0.38 0.0844

Potentiometers Out-Of-Range No Signal Sent To HV Vechicle Doesn't Move 1 (E), 1 (S), 2 (O), 1 (NO)

10 1 1.25 0.2778

Potentiometer Cease To Work No Signal Sent To MCU/HV

Vechicle Doesn't Move 1 (E), 1 (S), 2 (O), 1 (NO)

10 1 1.25 0.2778

HV Controller Ceases To Work No Signal Sent To MCU/HV

Vechicle Doesn't Move 1 (E), 1 (S), 2 (O), 1 (NO)

10 1 1.25 0.2778

Signal Wiring Damaged/ EMF Interference of Signal

Bad Signal Sent To MCU/HV

Vechicle Responds Erratically 1 (E), 1 (S), 2 (O), 1 (NO)

10 1 1.25 0.3086

Monitor State Of Sensors (Primary)

Accept Real-time Signals and write data to Removable Storage

Data Not Recorded

Encode Accelerator Pedal as a Torque

Signal to HV (Primary)

Vote Potentiometers (2+) of Accelerator

Pedal by +/- 10% and pass voted signal to

HV

Accelerator Pedal Does Not

Work

HVC Formula = (Rank/40)*R.O.D.* D

Function Performance Standards Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurren

Detectibility

Risk Ranking(1 = Lowest; 100 =

Normalized Rank (1= high, 0 = low)

Mitigation / Redesign Plan

Waveform Skewed Circuitry Damaged Poor/None Locomotion, Motor damaged

Vehicle Does Not Move, Motor Windings Damaged, HV must

1 (E), 1 (S), 10 (O), 5 (NO)

1 1 0.43 0.0944

Circuitry Fails to Convert DC to AC

Circuitry Damaged Poor/None Locomotion, Motor damaged

Vehicle Does Not Move, Motor Windings Damaged, HV must

1 (E), 1 (S), 10 (O), 5 (NO)

1 1 0.43 0.0944

Voltage Diminished Circuitry DamagedPoor/None Locomotion,

Motor damaged

Vehicle Does Not Move, Motor Windings Damaged, HV must

be ReplacedRepaired

1 (E), 1 (S), 10 (O), 5 (NO) 1 1 0.43 0.0944

Does Not Precharge Circuitry Damaged HVC Damaged due to Inrush current

HVC Damaged 1 (E), 1 (S), 10 (O), 5 (NO)

1 1 0.43 0.0944

Does Not Discharge Circuitry Damaged HVC Stays Charged Potential Shock Hazard 1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Rate Skewed Circuitry Damaged None Vehicle Unaffected 1 (E), 1 (S), 1 (O), 5 (NO)

1 1 0.20 0.1000

Does Not Receive Signal Communication Error/Line Noise

Poor/None Locomotion Vehicle Does Not Move, HV must be ReplacedRepaired

1 (E), 1 (S), 10 (O), 5 (NO)

1 1 0.43 0.0956

Does Not Enable Circuitry Damaged Poor/None Locomotion Vehicle Does Not Move, HV must be ReplacedRepaired

1 (E), 1 (S), 10 (O), 5 (NO)

1 1 0.43 0.0956

Convert VDC to VAC (Primary)

Convert 300 VDC to 300 VAC 3 Phase in Real-Time with No

Power Lag

Provide Pre-charge/Discharge

Circuitry (Primary)

1st Stage: 92% of HV Batt. Voltage 2nd Stage: 100% HV

Batt. Voltage ; All current under 5 Amps during Precharge

Provide Run-enable Capability (Primary)

Allow Power from HV Batteries to Motor after all

subsystems/disconnects enter “Ready to Run”

Page | 40

Master Safety Circuit

Formula = (Rank/40)*R.O.D.*

DFunction Performance Standards Functional

FailuresFailure Modes Failure Effects Consequence Category Rank (Total out of

40)Rate of

OccurrenceDetectibili

ty

Risk Ranking(1 = Lowest; 100 =

Highest)

Normalized Rank (1= high,

0 = low)Mitigation / Redesign Plan

Electrical Shock, Subsystem Damage, Vehicle Does Not Start, Subsystem Failure Indicator Light

Vehicle Non-Functional, Subsystem Must Be Replaced, Injured Personel

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

Electrical Shock, Subsystem Damage, Vehicle Does Not Shut Off, Subsystem Failure Indicator

Injured Personel, Components Must Be Replaced, Vehicle Unsafe

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

Component DamagedElectrical Shock, Subsystem Damage, Subsystem Failure

Indicator Light

Injured Personel, Components Must Be Replaced, Vehicle Unsafe

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

AIRs DamagedElectrical Shock, Subsystem

Damage, Vehicle Does Not Shut Off, Subsystem Failure Indicator

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 6 1 2.70 0.6000

Component Damaged

Electrical Shock, Subsystem Damage, Vehicle Does Not Shut Off, Subsystem Failure Indicator

Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

2 1 0.90 0.2000

Short Circuit upon Disconnect Removal

Electrical Shock, Subsystem Damage, Vehicle Does Not Shut Off, Subsystem Failure Indicator

Light

Injured Personel, Components Must Be Replaced, Vehicle Unsafe

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

Allow for Disconnect of LV Batteries from All

Subsystems

Short Circuit upon Disconnect Removal

Subsystem Damaged Components Must Be Replaced, Possible Subsystem Damage

1 (E), 2 (S), 10 (O), 5 (NO)

2 1 0.90 0.2000

Subsystem Does Not Signal Failure during

Failure

Electrical Shock,Batteries Explode/Catch Fire, Subsystem

Damaged

Vehicle Non-Functional, Subsystem Must Be Replaced, ACC Unusable,

Injured Personel

1 (E), 2 (S), 10 (O), 5 (NO) 0.90 0.2000

Light is Damaged Electrical Shock Personel Injured1 (E), 2 (S), 10 (O), 5

(NO) 2 1 0.90 0.2000

Connect/Disconnect Subsystems

(Primary)

Systematic “Start-up” Procedure for Vehicle

Subsystem Failure

Subsystem Damaged

Disconnect of HV Batteries from HVC

Does Not Disconnect HV Batteries from

HVC

Does Not Disconnect LV Batteries from LV Batteries

Indcate Subsystem Status vis Dash Light

Accumulator

Formula = (Rank/40)*R.O.D.*

Function Performance Standards Functional Failures

Failure Modes Failure Effects Consequence Category

Rank (Total out of 40)

Rate of Occurrence

Detectibility

Risk Ranking(1 = Lowest; 100 =

Normalized Rank (1= high, 0 = low)

Mitigation / Redesign Plan

BMS Controller Damaged Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Battery Cell(s) non-functional Battery cells explode/catch fire

OR BMS has unclearible erroor, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 6 1 2.70 0.6000

Microboards on cells Damaged Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

BMS Controller Damaged Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Battery Cell(s) non-functional Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

6 1 2.70 0.6000

Microboards on cells Damaged Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000Disconnect Accumulator

from LiPO Charger if charge current exceeds

rate of Z A

Charger Does Not Disconnect

BMS Controller/Current Sense Damaged

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

BMS Controller Damaged Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Charger/HVC Does Not

Disconnect

BMS Controller/Temperature Sense Damaged

Battery cells explode/catch fire, BMS Failure Indicator Light

Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

AIR Fails to Open Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Battery Cell(s) Over-temperature from Charge/Use

BMS turns off, BMS Failure Indicator Light

Vechicle Shuts down for cool down period

1 (E), 2 (S), 10 (O), 5 (NO)

9 1 4.05 0.9000

IMS Trips Due to Short of HV to LV system, IMS Failure

Vechicle Shuts down until Error is Corrected

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Battery cells explode/catch fire Vehicle Non-Functional, ACC Unusable

1 (E), 2 (S), 10 (O), 5 (NO)

1 1 0.45 0.1000

Monitor Temperature of 4.2 V LiPO cell

(Primary)

Disconnect Accumulator from LiPO Charger/HVC if

temperature of 30% of cells exceed 60⁰C HVC Does Not

Disconnect

Validate inter-cell connection of 4.2 V LiPO cells via TAP

(Primary)

Validate series/parallel connection of cells to

prevent damage main BMS Controller

TAP Gives False Validation TAP/BMS Damaged

Provide 160 DAC Continuous 250 DAC Maximum (Primary)

Disconnect Accumulator from LiPO Charger if X%

of accumulator cells exceeds 4.2 V

Charger Does Not Disconnect

Balance Y cells to equal Voltage

Cell(s) Do Not Balance

Monitor Current Output of 4.2 V LiPO cell(s)(Primary)

Disconnect Accumulator from HVC if operating

current exceeds Z A for T seconds

HVC Does Not Disconnect

Provide 300 VDC Nominal (Primary)

Disconnect Accumulator from LiPO Charger if

accumulator exceeds 300 VDC (Nominal)

Charger Does Not Disconnect

Balance Y cells to equal Charge

Cell(s) Do Not Balance

Motor

Formula = (Rank/40)*R.O.D.*

Function Performance Standards

Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurrence

Detectibility Risk Ranking(1 = Lowest; 100 =

Normalized Rank (1= high, 0 = low)

Mitigation / Redesign Plan

DC not properly converted to AC

Poor Performance Vehicle Non-Functional, Motor Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Motor Overtemperature

Poor Performance Vehicle Non-Functional until Motor cools down

1 (E), 2 (S), 10 (O), 1 (NO) 9 1 4.05 0.9000

Motor Windings Damaged

Poor Performance Vehicle Non-Functional, Motor Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

HVC Damaged Poor Performance Vehicle Non-Functional, HVC Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

DC not properly converted to AC

Vehicle Does Not Move Possible Motor Winding Damage 1 (E), 2 (S), 10 (O), 5 (NO) 10 1 4.50 1.0000

Motor Overtemperature

Vehicle Does Not Move Vehicle Non-Functional until Motor cools down

1 (E), 2 (S), 10 (O), 5 (NO) 9 1 4.05 0.9000

Motor Windings Damaged

Vehicle Does Not Move Vehicle Non-Functional, Motor Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Subsystem Failure Vehicle Does Not Move Vehicle Non-Functional, Subsystem Failure, Subsystem

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

AIRs Open Vehicle Does Not Move Vehicle Non-Functional, Subsystem Failure, Subsystem

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Traction System Damaged

Mechanical Failure Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 10 (O), 5 (NO) 6 1 2.70 0.6000

Differential Damaged Mechanical Failure Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 10 (O), 5 (NO) 6 1 2.70 0.6000

Motor Windings Damaged Vehicle Does Not Move

Vehicle Non-Functional, Motor Unusable 1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Subsystem Failure Vehicle Does Not MoveVehicle Non-Functional,

Subsystem Failure, Subsystem Damaged

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Motor Overtemperature Vehicle Does Not Move

Vehicle Non-Functional until Motor cools down 1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

AIRs Open Vehicle Does Not Move Vehicle Non-Functional, Motor Unusable

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000Motor Windings

DamagedVehicle Does Not Move Vehicle Non-Functional, Motor

Unusable1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Motor Overtemperature

Vehicle Does Not Move Vehicle Non-Functional until Motor cools down

1 (E), 2 (S), 10 (O), 5 (NO) 1 1 0.45 0.1000

Provide Locamotion to

Vehicle (Primary)

Operate at 300 VAC, 160 AAC

(Nominal)

Non-optimal Voltage/Amperage

No Voltage/Amperage

Drive Rear Differential

Motor Does Not Power

Motor Does Not Spin

Page | 41

Control Arms

Formula = (Rank/40)*R.O.D.* D

FunctionPerformance

Standards Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurrence DetectibilityRisk Ranking(1 =

Lowest; 100 = Highest)

Normalized Rank (1= high, 0

= low)

Bond failure Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 10 (O), 3 (NO) 2 1 0.8 0.1778

Rod Failure Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 10 (O), 4 (NO) 2 1 0.85 0.1889

Cracked Rod End Weaken of suspension components

Vehicle Functional but not advisable

1 (E), 2 (S), 10 (O), 3 (NO) 1 1 0.40 0.0889

Failed Rod End Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 10 (O), 3 (NO) 1 1 0.40 0.0889

Detachment of Carbon rods

Rod end failure

No play, Maintain

attachment point lengths

Attach the outer

suspension components to

the vehicle

Rocker Formula = (Rank/40)*R.O.D.* D

Function Performance Standards Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurrence Detectibility Risk Ranking(1 = Lowest; 100 = Highest) Normalized Rank (1= high, 0 = low)

Bending Bending Structure Weaken component, Possible seizing of suspension

Vehicle Functional but not advisable

1 (E), 1 (S), 8 (O), 3 (NO)

1 1 0.325 0.0722

Structure Fracture Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 8 (O), 3 (NO)

1 1 0.35 0.0778

Hole Fracture Vehicle Does Not Move Vehicle Non-Functional 1 (E), 2 (S), 8 (O), 3 (NO)

1 1 0.35 0.0778

Bending of Tabs Possible seizing of suspension Vehicle Functional but not advisable

1 (E), 1 (S), 8 (O), 3 (NO)

2 1 0.65 0.1444

Bearing Failure Possible seizing of suspension Vehicle Functional but not advisable

1 (E), 1 (S), 8 (O), 2 (NO)

2 1 0.6 0.1333

Unatachment of Components Fastener Failure Vehicle Does Not Move Vehicle Non-Functional

1 (E), 2 (S), 6 (O), 1 (NO) 2 1 0.5 0.1111

BreakingWithstands Force

Out of PlaneTransfer Force

Transfer Wheel movement to the coilover damper

Anti Roll Formula = (Rank/40)*R.O.D.* D

Function Performance Standards Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40) Rate of Occurrence

Detectibility Risk Ranking(1 = Lowest; 100 = Highest)

Normalized Rank (1= high, 0 = low)

Bending Poor Performance

Functional with altered performans

1 (E), 1 (S), 2 (O), 1 (NO) 2 2 0.5 0.1111

Fracture Poor Performance

Functional with altered performans

1 (E), 1 (S), 2 (O), 1 (NO) 1 1 0.125 0.0278

Detachment Poor Performance

Functional with altered performans

1 (E), 1 (S), 2 (O), 1 (NO) 2 2 0.5 0.1111

Twisting Poor Performance

Functional with altered performans

1 (E), 1 (S), 2 (O), 1 (NO) 2 2 0.5 0.1111

Bending Poor Performance

Functional with altered performans

1 (E), 1 (S), 2 (O), 1 (NO) 2 2 0.5 0.1111

FracturePoor

PerformanceFunctional with altered

performans 1 (E), 1 (S), 2 (O), 1 (NO) 1 1 0.125 0.0278

Blade failure

Bar Failure

Adjustable

L and R connection

Link Left and right suspension

together

DrivetrainFormula =

(Rank/40)*R.O.D.* D

Function Performance StandardsFunctional

FailuresFailure Modes Failure Effects Consequence Category

Rank (Total out of 40)

Rate of Occurrence Detectibility

Risk Ranking (1 = Lowest; 100 =

Highest)

Normalized Rank (1= high, 0

= low)

Mitigation / Redesign Plan

Chain breaks Car Immobility Vehicle Non-Functional 1 (E), 2 (S), 4 (O), 1 (NO)

3 1 0.60 0.1333

Chain derailment

Car Immobility Vehicle Non-Functional 1 (E), 2 (S), 4 (O), 1 (NO)

2 1 0.40 0.0889

Motor mounjt breaks

Car Immobility/Motor damage Vehicle Non-Functional

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

Bolt or tab breaks

Car Immobility/Motor damage Vehicle Non-Functional

1 (E), 2 (S), 10 (O), 5 (NO) 2 1 0.90 0.2000

Transmit torque from motor to

rear wheels

Effectivly transmit power to rear wheels Chain failure

Hold motor in placeMotor mount

failure

Sidepod

Function Performance Standards

Functional Failures Failure Modes Failure Effects Consequence Category Rank (Total out of 40)

Rate of Occurrence

Detectibility

Risk Ranking(1 = Lowest; 100 = Highest)

Normalized Rank (1= high,

0 = low)

Mitigation / Redesign

Plan

Quarter turn fasteners failure

Fail to Cool Batteries/ Possible crack

Vehicle Functional but not recommended

1 (E), 2 (S), 2 (O), 5 (NO)

1 1 0.25 0.0556

Sidepod tabs failure

Fail to Cool Batteries/ Possible crack

Vehicle Functional but not recommended

1 (E), 2 (S), 2 (O), 5 (NO)

1 1 0.25 0.0556

Cracked sidepod Fail to Cool Batteries Vehicle Functional but not recommended

1 (E), 1 (S), 2 (O), 5 (NO)

1 3 0.23 0.0500 Remake Sidepod

Sidepod movement Fail to Cool Batteries Vehicle Functional

1 (E), 1 (S), 2 (O), 1 (NO) 6 3 0.13 0.0278

Cooling the batteries

Effective airflow to battery case

Detachment from chassis

Failure to provide effective cooling to batteries

Page | 42

Works Cited

[1] SAE International, "FSAE Online," [Online]. Available: http://www.fsaeonline.com/content/2015-16%20FSAE%20Rules%20revision%2091714%20kz.pdf. [Accessed 28 September 2014].

Consequence Ranking Environmental Safety Operational Non-Operational Rate of Occurrence Detectability

1 No Impact on Environment. No Potential for Causing Injury.

Has no adverse effect on production.

Repair costs between $10 - $100 Once per BU lifetime Becomes evident immediately

upon failure

2Failure has potential for injury that only requires

first aid.

Causes an immediate slowdown of up to 2 hours

Repair costs between $100-$500

More than once per lifetime, but less often

than every 4 years

Becomes evident within one hour after failure

3 Causes an immediate slowdown of up to 1 shift

Repair costs between $500 -$1000

Once Every 2 to 4 Years

Becomes evident within one shift after failure

4 Causes an immediate shut down of a major unit for up to 2 hours

Repair costs between $1000 -$2,000 Once Every 1-2 Years Becomes evident within 2 days

after failure

5 Causes an immediate shut down of a major unit for up to 1 shift

Repair costs between $2,000 -$5,000 Once Every Year Becomes evident within 1 week

after failure

6 Causes an immediate shut down of a major unit for up to 24 hours

Repair costs between $5,000 -$10,000 Once half year Becomes evident within 2

weeks after failure

7 Causes an immediate shut down of a major unit for up to 3 days

Repair costs between $10,000 -$15,000 Once Every Quarter Becomes evident within 1

month after failure

8 Causes an immediate shut down of a major unit for up to 1 week

Repair costs between $15,000 -$25,000 Once Every Month Becomes evident within 3

months after failure

9Failure has potential for

injuries resulting in permanent disability

Causes an immediate shut down of a major unit for up to 10 days

Repair costs between $25,000 -$50,000 Once per week Becomes evident within 6

months after failure

10

Failure would cause a major discharge/release requiring

evacuation of presonnel, extensive clean up and

notification

Failure has high potential for fatality

Causes immediate complete shutdown of a major unit for a time long enough to deplete inventory

and result in a loss of sales

Repair costs exceed $50,000 Daily Becomes evident within one year after failure

Failure could result in minor environmental impact

including hazardous dust spill in secondary containment

Failure has potential for reportable incident.

Failure may result in discharge/release requiring

state or EPA notification. Failure of equipment that is

required for reporting purposes.

Failure would result in a discharge/release requiring state or EPA notification and

NOV.

Failure has potential for reportable incident with

lost time.