regenative braking system for illini formula electric
TRANSCRIPT
REGENATIVE BRAKING SYSTEM FOR
ILLINI FORMULA ELECTRIC
By
Nick Meinhart
Joshua Seibert
Final Report for ECE 445, Senior Design, Fall 2015
TA: Zitao Liao
9 December 2015
Project No. 08
ii
Abstract
The regenerative braking system is a combination of a logic circuit and current equipment on Illini
Formula Electric’s vehicle. The logic circuit determines whether or not regenerative braking is
possible based on current conditions of the vehicle’s state. The two variables that are used in
making this decision is the current battery charge level and speed. The battery charge must be at a
level in which overcharging will not occur and the speed of the vehicle must fall within a range in
which the vehicle is moving fast enough to create a charge and slow enough to not violate any
voltage or current limits. In order to create the charge the present vehicle’s motor is used and the
electric drive is used to rectify and deliver the charge. Testing of the logic circuit has produced
favorable results, but testing with the current vehicle has yet to take place.
iii
Contents
1. Introduction .....................................................................................................................................................................................1
1.1 Purpose ......................................................................................................................................................................................1
1.2 Objective ....................................................................................................................................................................................1
1.3 Function .....................................................................................................................................................................................1
1.4 Benefits.......................................................................................................................................................................................1
2 Design ..................................................................................................................................................................................................2
2.1 Battery Charge Circuit ........................................................................................................................................................3
2.2 Frequency to Voltage Circuit...........................................................................................................................................4
2.3 Speed Control Circuit ..........................................................................................................................................................6
2.4 AND Gate/MOSFET Circuit ..............................................................................................................................................7
2.5 12 to 5 Volt Convertor ........................................................................................................................................................8
2.6 Battery ........................................................................................................................................................................................8
2.7 Drive ............................................................................................................................................................................................8
2.8 Motor ...........................................................................................................................................................................................8
3. Design Verification .......................................................................................................................................................................9
3.1 Battery Charge Circuit ........................................................................................................................................................9
3.2 Frequency to Voltage Circuit........................................................................................................................................ 11
3.3 Speed Control Circuit ....................................................................................................................................................... 12
3.4 AND Gate/MOSFET Circuit ........................................................................................................................................... 13
3.5 12 to 5 Volt Convertor ..................................................................................................................................................... 13
3.6 Drive ......................................................................................................................................................................................... 14
4. Costs.................................................................................................................................................................................................. 15
4.1 Parts .......................................................................................................................................................................................... 15
4.2 Labor ........................................................................................................................................................................................ 15
5. Conclusion ..................................................................................................................................................................................... 17
5.1 Accomplishments............................................................................................................................................................... 17
5.2 Uncertainties ........................................................................................................................................................................ 17
5.3 Ethical considerations ..................................................................................................................................................... 17
5.4 Future work .......................................................................................................................................................................... 18
References .......................................................................................................................................................................................... 19
iv
Appendix A Abbreviations ..................................................................................................................................................... 20
Appendix B Requirement and Verification Table ...................................................................................................... 21
Appendix C Other Figures ...................................................................................................................................................... 24
1
1. Introduction
1.1 Purpose
Regenerative braking systems are used in today’s electric and hybrid vehicles in order to
capture and recover the kinetic energy that is lost as heat during conventional braking with
rotors and brake pads. These systems help improve the efficiency and driving range of the
vehicle per full charge of the battery. This project is to develop a regenerative braking
system for the Illini Formula Electric vehicle (IFE). The current vehicle is fully electric with
two batteries, a single drive system, and single motor. However, the vehicle’s range is
dependent on the combined charge capacity of the two batteries. With the addition of a
regenerative braking system, the range and efficiency of the current vehicle would
increase. The system we have planned in developing would be a system that recaptures
energy while the vehicle is coasting or braking. Conventional braking would still be present
and used when the driver uses the brake pedal.
1.2 Objectives
Increase the driving range of the Formula electric car given normal driving
conditions
Add a minimally invasive system without major modifications to the existing car
Add the least amount of weight possibly while still achieving significant gains
1.3 Functions
Stores kinetic energy of braking that can be used later as electrical energy
1.4 Benefits
Extends driving range of vehicle
Decreases wear on brakes
2
2 Design
This system consists of existing components present on IFE’s current vehicle and a
controller used to determine if regenerative braking can take place or not. An overall
system diagram can be seen in figure 1. The controller for regenerative braking can be
broken down into 4 simple logic circuits and a single 12 to 5 volt converter. The logic
circuits consist of the battery charge circuit, speed control circuit, frequency to voltage
circuit, and the AND gate/MOSFET circuit. The two variables that the controller takes in as
input is the charge level of the battery and the signal from the hall sensor. Both of these
sensors are currently part of IFE’s vehicle. A detailed diagram of the controller can be seen
in figure 2. Regenerative braking is activated by pulling the regen pin of the drive to
ground. This pin is number 26 of the drive. The battery will then begin to receive charge
from the motor and the vehicle will slow.
Figure 1: Overall System Block Diagram
3
2.1 Battery Charge Circuit
The battery charge circuitry takes in as an input the signal that gives the current charge
level of the battery. The sensor is already part of the current vehicle’s signals. This sensor
provides a voltage level that indicates the charge of the battery. The maximum voltage of
the sensor is 5 volts at a full charge and drops off linearly as the charge of the battery
drops. This circuit will use this signal and compare to a set voltage level of 4.5 volts. This
means that regenerative braking will only take place once the charge of the battery drops
down to 90% or below in which the battery charge sensor will be outputting 4.5 volts or
less. This will ensure that the battery will not be overcharged by using regenerative
braking with batteries already at full charge. The maximum charge present on the battery
for regenerative braking was a value that IFE gave as a specification for their vehicle. This
circuit can be seen in figure 3.
Figure 2: Controller Block Diagram
4
2.2 Frequency to Voltage Circuit
The Frequency to Voltage Circuit takes in the signal from the Hall Effect sensor on the gear of
the driveshaft of the vehicle. The circuit then produces a voltage as an output depending on the
frequency of the signal. This is done by using the LM2907 logic chip with two addition resistors
and capacitors. In addition, there is also a reference voltage that must be set in order to
accurately determine the frequency. This is so the logic chip knows when the signal falls low and
goes high. This circuit can be seen in figure 4.
Figure 3: Battery Charge Circuit
Figure 4: Frequency to Voltage Circuit
5
In order to determine the values of the two capacitors in two resistors, the following
equations were used.
Vout = Vcc ∗ frequency ∗ C1 ∗ R1 1
frequencymax =R2
C1 2
Vripple =Vcc
2∗C1
C2∗ (1 − R2 ∗ Frequency ∗ C1) 3
These equations were provided on the datasheet of the LM2907 logic chip. In equation 1,
Vout is the voltage value being sent to the Speed Control Circuit, Vcc is the voltage value of
the voltage source powering the circuit. In equation 2, frequency max is the maximum
attainable input frequency. In equation 3, Vripple is the ripple amount of the voltage during
a change in frequency. It corresponds to the amount of time it takes for the voltage to
stabilize. The first step to selecting these components was to determine the maximum
frequency which corresponds to the maximum speed limit of the car. The upper limit of the
motor speed desired for regen, given by IFE, was 5000 RPMs. With the car having a 3 to 1
gear ratio and 42 teeth on the gear of the drive shaft, this corresponds to a frequency of
1166.67 Hz. This was found by converting the 5000 RPMs to rotations per second, dividing
by 3 to get drive shaft rotation, and multiplying by 42 as this will be the amount of times
that the hall sensor will output a high signal. Then by using equation 1 and 2, we could plug
in values for the desired Vout, Vcc, frequency and frequency max. Here frequency and
frequency max are the same at 3500 Hz and Vout is lower than Vcc in order to not operate
the circuit near the cutoff range of obtainable maximum frequency. We arbitrarily chose 3
volts for Vout as this is far under our maximum limit of Vout. This leads three unknowns in
which we decided to assign a value to C1. We picked small values that could be obtained at
the ECE shop as this will lead to a small voltage ripple as can be seen in equation 3. The
value for C1 that we ended up choosing was 3.9 nF. This will lead to R1 and R2 to be 50 kΩ
and 160 kΩ respectively. As it can be seen C2 does not impact frequency max or Vout, so we
were free to choose C2 when calculating Vripple in equation 3. We choose to go with a
value much larger that C1 in order to minimize Vripple. This value was 1.0 µF. Figure 5
displays the plot of the Vripple and Vout with the relationship between voltage and
frequency.
6
As it can be seen, when the frequency increases, Vout increases and Vripple decreases. This
is the desired operation of this circuit and thus is used to determine speed. The output
voltage, or Vout, is then sent to the Speed Control Circuit.
2.3 Speed Control Circuit
The Speed Control Circuit, seen in figure 6, determines if the vehicle is going at a speed that
would allow for regenerative braking. This circuit will use two comparators with one
determining if the vehicle is going fast enough and the other determining if the vehicle is
going slow enough. If the car is going too slow, the driver may not want a braking action as
they might be simply trying to position the vehicle into a spot such as the starting position
in a race. This will also eliminate the chance of regenerative braking when crew members
are pushing the vehicle in which the crew will not have to overcome the braking force.
Speeds that are too fast are speeds in which the voltage created by the motor would be too
high and damage the batteries. The voltages that are set as comparison values with the
input from the Frequency to Voltage Circuit are based on the speed of the vehicle.
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 2 4 6 8 10
Fre
qu
en
cy (H
z)
Voltage (V)
Vout and Vripple Plots
Vripple
Vout
Figure 5: Vout and Vripple Plot
7
2.4 AND Gate/MOSFET Circuit
The AND Gate/MOSFET Circuit is the last part of the overall logic circuit. This circuit takes
in the three inputs; one from the battery charge circuit and two from the speed control
circuit. The circuit then produces a signal via the output of the AND gate and then the
signal is then sent to the gate of the MOSFET. The MOSFET will close and pull the regen pin
of the drive to ground with a high signal and remain open with a low signal. This circuit can
be seen in figure 7. This circuit also includes a 1 kΩ resistor which is used simply as a pull
down resistor to ensure that the gate of the MOSFET does not float high. This value was
arbitrarily picked and tested.
Figure 6: Speed Control Circuit
Figure 7: AND Gate/MOSFET Circuit
8
2.5 12 to 5 Volt DC Convertor
The 12 to 5 Volt DC Converter is to step down the voltage of the available 12 V system on
IFE’s vehicle in order to provide the Battery Charge Circuit the correct voltage for
comparison. This convertor was purchased from Super Bright LEDS.
2.6 Battery
The battery component is already part of the current electrical system of the car. This
component actually consists of two batteries each of which are capable of 50 amp
discharge current, and 10 amp charge current. Each individual battery consist of smaller
cells that have a voltage level of 4.1 V at maximum charge and a 3.7 nominal voltage level.
There already exists a battery level sensor that we plan on using in order to determine if
the battery can accept any charge.
2.7 Drive
The drive is a variable frequency electric drive by Sevcon. The model is Gen 4 Size 8.The
drive is already being used in the current electrical system of car with it primary purpose
being to convert the DC voltage from the battery to AC voltage for the motor. This
component will be used in the regenerative braking design as a rectifier as it also has the
ability to rectify the AC voltage from the motor to DC voltage. This component will also be
used in limiting the current to a maximum of 10 amps. This restriction will inhibit the
regenerative capabilities, but is required in order to not damage the batteries. This is done
by the drive and is enabled by software present on the drive.
2.8 Motor
The motor/generator is an existing component on the vehicle by YASA Motors. The motor
is a 4 pole, permanent magnet, synchronous motor. This motor has a maximum rpm of
7500 at 340 Newton meters. This motor is ideal for regenerative braking as the rotor
requires no excitation current in order to create current in the rotors. This is because of the
permanent magnet which will provide the flux. The back electromotive force (EMF) of the
motor is 0.062 Vrms/rpm.
9
3 Design Verification
Testing of our design involved testing each circuit of the controller individually. Once all
four circuits were working as expected, we tested the controller as a whole. Once this was
done, we were finally able to assembly the controller on the PCB.
3.1 Battery Charge Circuit
Testing of the battery charge circuit first took place on the breadboard. The variable resistor of
this circuit was set to only drop 0.5 V. This sets the comparison voltage at pin 3 to 4.505 V
which relates to 90% battery charge. This was a specification given by IFE. Once the
potentiometer was adjusted, a secondary voltage from a voltage supply was applied to pin 2 of
the circuit which represented the battery charge sensor. This voltage was initially set at 0 V and
was increased by 0.5 V until the voltage was 5 V. At each 0.5 V increase, the output voltage of
pin 1 was measured. As the results show in table 1, the output of the circuit was high with a
simulated battery sensor voltage from 0 to 4.5 V. Once 5 V was reached, however, the output
voltage dropped to 39 mV which corresponds to a low voltage output. From these results, it was
concluded that the Battery Charge Circuit functions properly.
Later it was tested how sensitive the comparator was around the cutoff voltage for regenerative
braking, or the set comparison voltage. This testing was to see if the circuit would bounce the
output high and low when a voltage from the battery sensor was equal to or approximately equal
to the comparison voltage. This was tested by increase voltage by 0.001 V from 4.5 V till the
output went low as can be seen in figure 8. It was also tested by decreasing the voltage by 0.001
V from 4.510 V till the output went high as can be seen in figure 9. As the results show, the
comparator does very well and keeps a steep fall off point. From these results, we concluded that
the circuit would not bounce as the circuit output falls by 5 V over a 0.003 voltage span
.
Table 1: Battery Charge Circuit Testing Results
Simulation Voltage (V) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Comparator
Output (V) 5.01 5.01 5.01 5.01 5.01 5.01 5.01 5.01 5.01 5.01 0
10
Figure 8: Battery Charge Circuit characteristics with increasing voltage
Figure 9: Battery Charge Circuit characteristics with decreasing voltage
11
3.2 Frequency to Voltage Circuit
Testing of the Frequency to Voltage Circuit started by holding pin 8 to ground rather than
hold it to some voltage by means of the potentiometer. This was to make sure the circuit
would work with general inputs and then we would adjust the circuit for the Hall Sensor.
The circuit was then given an input of a square wave, at 1 Hz, and 2 V peak-to-peak with a
function generator. The starting frequency was 1 Hz as this was as low as the function
generator could go. Here the output voltage was then recorded at pin 4. The frequency was
then adjusted up to 500 Hz and the output was recorded again. This was done till the
frequency was up to 4000 Hz in 500 Hz increments. As it can be seen in figure 10, the
theoretical curve produced by equation 1 fits almost exactly on top of measured curve.
With this, the potentiometer was adjusted to hold a voltage of 0.5 V at pin 8 and the square
wave was changed to have an offset value of 1V. This was to test the circuit and make sure
that it would work without an input signal that goes negative. This is why the
potentiometer is needed so as the circuit knows when the signal rises and falls. The results
can be seen plotted in figure 11 and it can be seen that the results are similar as those seen
in figure 10.
With these results, it can be seen that the circuit outputs an increased voltage value with
increased frequency. It was then concluded that this circuit works as expected.
Figure 10: Theoretical and Measured Output Curves
12
3.3 Speed Control Circuit
The testing for this circuit was similar to that of the battery charge sensor circuit which
first began by setting the values of the potentiometers. The potentiometers were adjusted
until voltages of 8.8 V and 0.85 V were obtained at pins 2 and 5 respectively. The voltages
were set far apart to test the range of the comparators. Once the potentiometers were set,
an input voltage simulating the input from the Frequency to Voltage circuit was applied to
pins 3 and 6. This voltage was first set at 0 V and was incremented up to 10 V in 1 V
increments. The results that should be expected is that pin 3 should output an high voltage
of roughly 12 V while the voltage at pin 3 is below 8.8V and the voltage at pin 5 should have
a low voltage of about 0 V until the voltage at pin 6 is above 0.85 V. Table 2 records these
results. As it can be see, the circuit worked as expected.
Table 2: Speed Control Circuit Results
Input simulation voltage (V)
0 1 2 3 4 5 6 7 8 9 10
Low voltage comparison output (V)
0.02 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9
High voltage comparison output (V)
11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 0.02 0.02
Figure 11: Frequency to Voltage Results with adjusted potentiometer
13
3.4 AND Gate/MOSFET Circuit
The AND Gate/MOSFET Circuit was tested first by making sure that the 3-input AND gate
was working properly. This was done by applying 5V to pin 14 and ground to pin 7. Then
the voltage output of pin 6 was measured while pins 3, 4, and 5 where given varying inputs
of 0 V and 5 V. Table 3 gives the results of all 8 possibilities. From these results, it was
concluded that the AND gate was working correctly.
To test the MOSFET, pin 1 was given 5 V while pin 2 was tied to ground. Then the voltage
difference across the MOSFET was measured to be 1 V. This seems high, but is expected to
still work as switch for the drive. Then 5 V was applied to pin 3 of the MOSFET and the
voltage difference was measured between pin 1 and 2. This voltage was found to be 0.09 V.
This is an acceptable voltage to the pin of the drive to ground to allow regen.
Once the two components of the circuit were verified to be working, the output of the AND
gate was tied to the gate of the MOSFET and the circuit was tested again. This was to see if
the AND gate could switch the MOSFET on and off. While applying 5 V to pins 3, 4, and 5,
the voltage across the MOSFET was found to be 0.09 V. This means the MOSFET was closed.
It was then concluded that this circuit worked as intended.
Table 3: AND Gate Testing Results
3.5 12 to 5 Volt Converter
Testing of the voltage converter was simple. Voltages of 11 V, 12 V, and 13 V were applied
to the leads of the converter while the output was measured. It was found that the
measured output voltage for the input voltages were 4.92 V, 5.01 V, and 5.1 V respectively.
We then concluded that the converter worked.
pin 3 voltage (V)
0 5 0 5 0 5 0 5
pin 4 voltage (V)
0 0 5 5 0 0 5 5
pin 5 voltage (V)
0 0 0 0 5 5 5 5
pin 6 voltage (V)
0 0 0 0 0 0 0 5
14
3.6 Drive
Testing of the drive unfortunately could not take place. This was due to complications of
other vehicle components that rendered the car inoperable. Testing for this vehicle was
simply to run the motor up to 500 RPM and then let the motor idle down. This was to be
done with pin 26 tied to ground. During this test, the current of leads on the batteries
would be measured. A negative current would have indicated that current was flowing into
the batteries and thus regenerative braking was programmed correctly on the drive. This is
a test that will have to be done in the future.
15
4. Costs
The total cost of the project, including parts and labor, is $29,329.10. The cost is broken
down between parts and labor in the following sections.
4.1 Parts
This part list included all the parts used in making the controller. Other parts, such as the
drive, motor, and battery were not included as they were already being used by IFE.
Table 4 Parts Costs
Item Part Number/Value
Manufacturer Quantity Unit Cost ($ each)
Actual Cost ($ total)
Comparator LT1017CN8 Linear Technology 2 $2.42 $4.84 IC Frequency
to Voltage LM2907N-8 Texas Instruments 1 $1.79 $1.79
12/5 V Converter
LVC-12V5-3A Super Bright LEDs 1 $9.95 $9.95
N-MOSFET* MPF102 Fairchild Semiconductor
1 Obsolete $0.00
3-input AND Gate*
SN74LS11N Texas Instruments 1 $0.81 $0.00
Capacitor* .0039 µF TDK Corporation 1 $0.24 $0.00 Capacitor* 1.0 µF Murata Electronics 1 $0.10 $0.00
Potentiometer* 500 kΩ BI Technologies 3 $1.61 $0.00 Potentiometer* 1 MΩ BI Technologies 1 $1.61 $0.00
Resistor* 160 kΩ Ohmite 1 $0.71 $0.00 Resistor* 50 kΩ Ohmite 1 $0.70 $0.00 Resistor* 1kΩ Ohmite 1 $0.70 $0.00
Wire* 16 AWG - 3 ft $0.11/ft $0.00 Alligator Clip* BU-60S Mueller Electric 6 $0.45 $0.00
Total $16.58
It is important to note here that this table only represents the cost of the item and does not
include shipping or taxes. All items noted with an asterisk were obtained in the ECE shop
and thus were obtained for free.
4.2 Labor
The labor was calculated assuming a $33.50 hourly rate for both team members and an
estimated 175 hours of work. Then a multiply of 2.5 was applied to cover insurance and
other business related cost that comes with the typical engineering position. This comes to
a total cost of $29,312.50. Table 5 summarizes the labor cost.
16
Table 4: Labor Cost
Engineer Hourly Rate
Total Hours
Total = Hourly Rate X 2.5 X Total Hours
Nick Meinhart
$33.50 175 $14,656.25
Joshua Seibert
$33.50 175 $14,656.25
Total $29,312.50
17
5. Conclusion
5.1 Accomplishments
Although there were unexpected obstacles and delays along the way, a functional control
circuit was designed and successfully built for the IFE team. Since there were some
setbacks that prevented testing and data collection, a debugging/explanatory manual was
constructed and provided to the team along with a safety manual. All requirements for
regen to take place have be met and verified through lab simulations.
5.2 Uncertainties
Throughout the semester, many obstacles would arise. The first was the low voltage
problem with the IFE car. This made the motor unable to spin, therefore hindering our
ability to perform test with the circuit on the car. Second was the unexpected differential
leak. The leak prevented the car from being run at reasonable race speeds, but the IFE
team was able to get the car running for a short period of time. The differential leak
worsened and finally had to be removed from the car and sent back to the manufacturer for
reconstruction. This further complicated our work because the signal from the hall sensor
connected to the gears could not be extracted for testing. Another major uncertainty that
became present late in the semester was controlling pin 26 on the drive. Working with IFE
team members, it was believed that a simply high/low voltage could be applied to pin 26 to
control regen. However, it was discovered that the pin must be pulled to ground in order to
operate regen. This meant designing an entire new circuit that needed to be added to the
PCB. The problem was solved with the addition of the MOSFET to the output of the AND
Gate to properly pull the pin to ground.
5.3 Ethical considerations
Below is a partial list of the IEEE Code of Ethics
1. to accept responsibility in making decisions consistent with the safety, health, and
welfare of the public, and to disclose promptly factors that might endanger the public or
the environment;
2. to avoid injuring others, their property, reputation, or employment by false or
malicious action;
3. to be honest and realistic in stating claims or estimates based on available data;
18
4. to improve the understanding of technology; its appropriate application, and potential
consequences;
5. to maintain and improve our technical competence and to undertake technological
tasks for others only if qualified by training or experience, or after full disclosure of
pertinent limitations;
The first two topics listed above are our biggest ethical issues for the project. It is
extremely important that our added design does not cause harm to any member of the IFE
team or damage their car or components in anyway.
The third topic is also very vital in our testing phase. Data collected while testing must be
accurate. This means the test must not be bias or that data is not altered to give a more
desired reading than what is actually measured.
The last two topics on the above list pertain to our personal development. The goal of this
class is to further develop our understanding of design, engineering and specifically
electrical engineering. We must further our understanding of each throughout our project.
The fifth topic also relates to topic concerning interacting with the IFE car. For our project,
we will need to alter the programming of the drive on the car. Responsibility must be taken
and ensure that changes are only made with consent from an appropriate IFE team
member.
5.4 Future work
Due to the complications with the IFE car, initial proposals of testing and collecting data
were unable to be accomplished this semester. The first step of future work will be to test
the control circuit with the IFE car. Once installed, test will need to be performed and
resistance values altered on the variable resistors. Data will need to be collected to
determine the top effective speed for regen. Once this is determined, values on components
in the frequency to voltage circuit will most likely need to be changed. IFE is being
supplied with any extra parts not used on the current PCB for many reasons. The first is in
case a component fails, it can be replaced quickly. Secondly, with all the testing that will
need to be done and the possibility of changing components in the frequency to voltage
circuit, it may be easier for the IFE team to duplicate the current PCB. This task will be
easier with the spare parts instead of the ones currently being used.
19
References
[1] Linear Technology Micropower Dual Comparator, datasheet, Linear Technology, Inc.,
2008. Available at: http://www.linear.com/product/LT1017
[2] LM2907 Frequency to Voltage Converter, datasheet, Texas Instruments, 2013. Available
at: http://www.ti.com.cn/cn/lit/ds/symlink/lm2917-n.pdf
[3] SN74LS11 Triple 3-Input Positive-AND Gates, datasheet, Texas Instruments, 1988.
Available at: http://www.ti.com/lit/ds/symlink/sn54s11.pdf
[4] MPF102 N-Channel RF Amplifier, datasheet, Fairchild Semiconductors, 2004. Available
at: https://www.fairchildsemi.com/datasheets/MP/MPF102.pdf
[5] Gen 4 Size 8: Applications Reference Manual, Rev 3.2, Sevcon, 2006.
[6] Seki H., Ishihara K., Tadakuma, Susumu. “Novel Regenerative Braking Control of
Electric Power-Assisted Wheelchair for Safety Downhill Driving”, Industrial Electronics,
IEEE, Vol.56, pp 1393-1400. Feb. 2009
20
Appendix A Abbreviations
Unit or Term Symbol or Abbreviation
ampere electromotive force farad
amp EMF F
hertz Illini Formula Electric kilohm kilovolt millivolt nanofarad ohm root-mean-square rotations per minute
Hz IFE
kΩ kV mV nF Ω rms rpm
volt V
21
Appendix B Requirement and Verification Table
Component Requirements Verification Verified
(Y or N)
Battery Charge
Circuit
This component should
provide a signal that is used to
determine if regen should be
allowed or not. The signal that
is sent out should be within
normal logic voltage ranges
(5V±0.5 for high and 1V±0.5
for low).
Set voltage comparison level
should be 4.5V±0.1 (indicates
90% battery charge) while
other voltage level will vary.
1. Apply a 5 volt signal to the
step down resistors and measure
voltage going into the
comparator for 4.5V.
2. Apply a voltage signal of
4.45 V to other input of
comparator and measure output
for ~5V.
3. Apply a voltage signal of
4.55V (or 4.65V if set level is
4.6V) and measure for output
~1V
Y
Speed Control
Circuit
This component should
provide 2 digital signals that
will both be used to determine
if regen is allowed or not.
These signals come from the
comparators and should be
12V±0.5 for a high signal and
0V±0.5 for low. The input
signal comes from the
frequency to voltage circuit
and will vary depending on
speed of the car.
1. Apply a 12 volt signal to the
variable step down resistors and
measure voltages going into the
comparators.
2. Adjust variable resistors till
desired voltage is less than or
equal to the voltage coming out
of frequency to voltage circuit
for top speed frequency
(8.5V±0.5) is read into top
comparator and desired voltage
is greater than or equal to
voltage coming out of frequency
to voltage circuit for low speed
frequency (0.88V±0.5) is read
into the bottom comparator.
3. Measure voltages into
comparators.
4. Apply a voltage (1-8V)
between the two set voltages to
the other comparators input and
measure for high output on both
comparators (12V±0.5).
5.Apply a voltage above the high
set voltage to other comparators
inputs and measure for a high
output (12V±0.5) on low
comparator and low voltage
output on high comparator
Y
22
(0V±0.5)
6. Apply a voltage below the low
set voltage to other comparators
inputs and measure for a low
output (0V±0.5) on low
comparator and high voltage
output on high comparator
(12V±0.5)
Frequency to
voltage Circuit
This component consist of the
Texas Instruments chip
LM2907, two capacitors, and
two resistors. The function of
this circuit is to take in the hall
sensor input and output a
certain voltage level depending
on the frequency of the circuit.
This circuit takes 12V to power
and output a DC voltage the
changes linearly with a change
in frequency.
1. Apply 12V to power the
circuit at pins 5 and 6
2. Apply a square wave with a
function generator. Set the
frequency at 100 Hz and set
amplitude to 2 V and offset of
1V
3. While measuring DC voltage
of pin 4 (or 7) increase the
frequency of the function
generator. The voltage should
increase.
4. While measuring the DC
voltage of pin 4 (or 7) decrease
the frequency of the function
generator. The voltage should
decrease.
6. Voltage output does
depending on voltage powering
the circuit. At 12V, pin 4 should
output 0.75±0.15 Volts at 375
Hz and should output 8.5±0.15
volts at 3750 Hz
Y
12/5 Volt
converter
This component should take in
12V±1.0 and output 5±0.5V.
The 12V will be supplied by
the existing 12V system on the
vehicle.
1. Apply 12V to the input and
measure the output for 5±0.5V
2. Apply 13V to the input and
measure the output for 5±0.5V
3. Apply 11V to the input and
measure the output for 5±0.5V
Y
23
AND Gate
with MOSFET
This circuit is uses an 3 input
AND gate that takes its inputs
from the battery charge circuit
and speed circuit. The AND
gate will then send a high
voltage to the gate of the
MOSFET which will then pull
pin 26 of the drive to ground
voltage.
NOTE: This verification is to be
done on the breadboard
1. Apply 5 volts to pin 14 of the
AND gate and ground pin 7.
Apply a voltage of 5V to pins 3,
4, and 5 and measure for a
voltage of 5±0.5 V from pin 6
2. Apply 5 volt to the drain of
the MOSFET(pin1) and ground
to the source (pin 2). Measure
the voltage difference between
the two pins. This should be ~1
volt.
3. Apply 5V to the gate (pin 3)
and measure the voltage
difference between pins 1 and 2.
Should measure ~0V or less than
the voltage measure before.
4. Attach pin 6 to the gate of the
MOSFET and apply 5 volts to
pins 3, 4, and 5. Measure the
difference between pins 1 and 2
of the MOSFET. Should
measure below 1 volt.
Y
Drive
This component takes in the 3
phase AC voltage from the
motor in regen and outputs DC.
This component needs to limit
the current to a maximum of 9
amps in order to not damage
the batteries. This component
also will be taking in the signal
to allow regen or not. This
drive will have to programed
for these requirements to be
met
1. After programming drive and
putting car on jack stands,
accelerate vehicle up to a speed
where the motor is spinning at
5000 rpms. Then let off
accelerator and measure current
flow from regen. Should be ~9A
2. Attach output signal from
controller and test three different
mode and measure currents in all
three modes.(no regen ~0A, low
regen ~5 amps, high regen ~9A)
N
24
Appendix C Additional Figures
Figure 12: PCB Circuit Diagram
25
Figure 13: PCB Board Diagram