Table of Contents

Project Scope ……………………………………………………………………………………………. 1 Logbook ………………………………………………………………………………………………….. 1

o Gantt chart for project process ……………………………………………………..3o Project emails records ………………………………………………………………….. 4o Project QFD ……………………………………………………………………………………. 11

Literature and Patent survey …………………………………………………………………… 12 Brainstorming/concept generation and free hand sketches ……………………… 13

o Early Lego model ............................................................................... 16 Design Feasibility Analysis ………………………………………………………………………… 16 Final design concept selection ………………………………………………………………….. 17

o Gripper ………………………………………………………………………………...………. 17o Two degree of freedom …………………………………………………………………. 18o Differential gear system & worm gears …………………………………………. 19o Stationary base ………………………………………………………………………………. 20o Touch sensors and Timing ……………………………………………………………….20

Project QFD ………………………………………………………………………………………………… 2 Lego Mindstorm Program …………………………………………………………………………… 21 Fem Report & Images ………………………………………………………………………………… 22

o Loads ………………………………………………………………………………………………. 22o Constraints ……………………………………………………………………………………… 23o Structural results ……………………………………………………………………………..24o Images …………………………………………………………………………………………….. 25

Maintenance Guide ……………………………………………………………………………………… 26 Safety Factor Calculation ……………………………………………………………………………… 27 Bibliography …………………………………………………………………………………………………. 28

Document scope

The project required a device to be built that could grab 3 different sizes of tires one at a time from 1-3 separate input locations, rotate the tire 180 degrees around an axis parallel to the shop floor, then place the tire on a single universal output location. Two tires of same size must be stacked on top of each other, only two motors can be used, and bonus marks are given if the device can service more than one input location.

After brainstorming and generating a concept, a design was created using NX Unigraphics, as well as a Lego prototype used to prove functionality.

LogbookTask Name Duration Start FinishRobot Arm Project 49 days Mon 26/09/11 Thu 01/12/11First Meeting-Getting to know the group members -Exchanging contact information -Deciding on where and when to meet next

1 day Mon 26/09/11 Mon 26/09/11

Project Overview-Discussion of the project requirements -Assigning the roles and splitting the parts for completion -Deciding who has the needed skill level to complete a certain task

1 day Wed 28/09/11 Wed 28/09/11

Brain Storming Session-Brief session on deciding what will be done for the design of the robot arm-Drawing up some sketches and sharing ideas for making a workable deign- Literature review on the existing robot designs

1 day Mon 03/10/11 Mon 03/10/11

"Drop Box" File Sharing Initiated-group members can now share the files with the group members online

1 day Wed 05/10/11 Wed 05/10/11

Preliminary Prototype- First prototype made with LEGO- Helped to orient the efforts and get on the same page

Milestone Fri 21/10/11 Fri 21/10/11

Preliminary Design, Basic Prototype, and Skill Gathering- Determining what skills need to be obtained to complete the project - Working with the basic prototype and improving it based on the set requirements

1 day Fri 21/10/11 Fri 21/10/11

Project Clarification 1 day Mon 24/10/11 Mon 24/10/11

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-Briefing on what needs to be completed and where the team Working on Prototype-Working with LEGO to make a good design 3 days Sun 06/11/11 Tue 08/11/11

Working on Prototype 1 day Tue 08/11/11 Tue 08/11/11Working on Prototype 1 day Sun 13/11/11 Sun 13/11/11Functional prototype made- The final prototype is established Milestone Mon 14/11/11 Mon 14/11/11

Making parts in CAD-Creating the parts for the real-world robot arm based on the prototype

6 days Tue 15/11/11 Tue 22/11/11

CAD parts are finalized-The parts are ready for drafting Milestone Tue 29/11/11 Tue 29/11/11

Drafting parts in CAD 2 days Tue 29/11/11 Wed 30/11/11CAD Drafting is Complete Milestone Wed 30/11/11 Wed 30/11/11FEM Simulation of Holding Jaw 3 days Mon 28/11/11 Wed 30/11/11FEM Simulation is Complete Milestone Wed 30/11/11 Wed 30/11/11Motion Simulation of the robot assembly 2 days Tue 29/11/11 Wed 30/11/11Motion Simulation is Complete Milestone Wed 30/11/11 Wed 30/11/11

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Gantt Chart for the Project Progress:

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Project QFD

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Literature and patent surveyThe JP 6262699 is a device used to grab tires one by one from a rack, and then move them to a

pre-determined location. The hand has 4 fingers that grab the tire from an upright position. This allows the arm to grab a fairly wide variety of sizes of tires compared with our concept which grabs tires from a horizontal position using two fingers. The JP 6262699 also has a much wider range of motion due to it having 3 joints each with their own axis of rotation yielding six degrees of freedom, allowing the device to be used in a more diverse range of operations. Our design would have a similar range of motion if we had more parts to work with, and weren’t limited by only being allowed to use 2 motors. Although the JP 626699 has a wider range of motion, it is only capable of rotating from 0-90 degrees around the Y-axis, meaning it cannot flip tires over 180 degrees as our design must. Both designs only have one arm and one hand, and can only move on tire at a time. Both designs must be installed in the floor, meaning there is little to no mobility.

The CN 101691033 is a robot for handling tires on a catenary coating line. A ball screw drives a moving seat and upper components along moving direction of catenary, a waist rotates with respect to the moving seat, a lower arm swings with respect to the waist, an upper arm swings with respect to the lower arm, a wrist rotates and swings with respect to the upper arm, and a pneumatic wheel gripper is located at the end of the wrist. This creates a much greater degree of freedom than our design, allowing for a wider range of motion and greater diversity of applications. A fixed camera is used to dynamically locate position of valve holes. This allows tires to be transported to and from unfixed points since the camera is able to gather the information required to determine the orientation of each part of the robot. This means the process can be changed without needing to alter the design or reprogram the

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robot. Our design would require alterations and reprogramming if the process were to be changed. The design is reliable and quick in gripping and handling, and is very accurate in positioning. The design must be installed to the floor resulting in little to no mobility. Also, the design only has one arm/hand, so it can only move one tire at a time.

Brainstorming/Concept Generation & Freehand Sketches

The project required a device to be built that could grab 3 different sizes of tires one at a time from 1-3 separate input locations, rotate the tire 180 degrees around an axis parallel to the shop floor, then place the tire on a single universal output location. Two tires of same size must be stacked on top of each other, only two motors can be used, and bonus marks are given if the device can service more than one input location.

The group agreed the simplest design of a gripper is simply two fingers that close in on either end of a horizontally oriented tire. A four fingered “claw” type approach was briefly considered, but was considered infeasible using only the given Lego. Either both fingers could move towards each other

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simultaneously, or one mobile finger could move towards the other stationary finger. The decision to have to parallel fingers move towards each other at the same rate would be made further down the road when more constraints and interdependencies were known.

In order to flip the tire over 180 degrees, the tire could be flipped by rotating a wrist, or by rotating the entire arm. It was agreed to make the entire arm flip to best comply with the project specifications.Flipping the entire arm requires a great deal more torque than rotating the tire using a wrist. Using a worm gear assembly was suggested then later implemented to compensate for this, since worm gears are capable of generating relatively large amounts of torque.

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The group agreed that all three input locations would be serviced in order to get the maximum possible bonus marks. This creates the challenge of requiring three distinct types of motion from two motors. In order to create three types of motion (opening/closing gripper, flipping the tire, and moving tire from input to output location) using only two motors, one of the motors must create two types of motion while the other creates one. The exact route we would take to do this could not be known during the brainstorming stage, but it was agreed that a differential gear system would be used to create two ranges of motion from one motor. The specific mechanics involving the differential gear system were worked out while building the model in order to ensure our ideas would comply with the limited supply of parts. The first motor would simply rotate the entire assembly around the Z-axis to move the arm from input locations to output locations, and the second motor would both flip the tire and open/close the grippers.

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Early Lego model:

This model was an early attempt to use one motor to both open/close the gripper, and flip the tire over. This concept was scrapped because it did not function very well, was unreliable, and the group wanted to try using a differential gear system.

Design Feasibility AnalysisThe design is very simple, functional, and cost effective, making it particularly feasible. The arm

has only two degrees of freedom when compared with the usual 6 degrees of freedom of modern industrial robot arms, but it still completes its required tasks without a hitch. Reducing the degrees of freedom to the minimum number greatly simplifies the design and reduces the total number of parts. These both decrease the overall cost of the design, and makes tasks such as maintenance much simpler.

The design does not allow for any dynamic changes such as altered location of input/output conveyor, but this is acceptable and feasible within the scope of the project.

The technology used in the system is extremely simple and feasible. Input from two seperate touch sensors are sent to a controller, which in turn tells the motors how to move for the given situation. Such a simple system avoids potential complications.

From an economic standpoint, the design is very feasible. It is comprised of 17,000 kilograms of aluminum (compared with max tire weight of 50 Kg) and consists of 39 unique components, resulting in a total cost of around $30,000-$50,000 per production. More complex robot arms used for similar purposes typically cost in excess of $100,000, making the design particularly economically feasible. The project required a device to be built that could grab 3 different sizes of tires one at a time from 1-3

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separate input locations, rotate the tire 180 degrees around an axis parallel to the shop floor, then place the tire on a single universal output location. The design meets all of these specifications, and is much cheaper than alternatives, which suggests sales would be excellent with proper marketing. Using an estimated sale price of $50,000-$60,000, it would only take 1-2 years for a company to warrant buying the machine when compared with hiring an employee to perform this task.

Final design concept selectionRobotic arm with 2 degrees of motion 2-prong parallel gripper, 360 degrees of motion in X-Y plane, and 180 degrees of motion in Z-Y plane.

Gripper:

The 2-prong parallel gripper was chosen for our design over other considered grippers. This option effectively accomplishes our given mission, while remaining relatively simple to achieve. Using the 4-bar mechanism to keep the two prongs parallel, we achieve the desired movement and sufficient equal pressure on a tire from both prongs.

Another feature of the gripper is the driver thatrotates the gears of the 4-bar mechanism. A high-torque worm-gear is used to give good grip strength on the tire, while at the same time back-pressure from the gripper cannot rotate the worm-gear. This is because the angle of the worm is set so that the friction between the gear and the worm is too great for the gear to overcome without massive amounts of torque. Effectively, the worm-gear locks the grippers until the worm-gear itself is driven when prompted.

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Two Degrees of Freedom:

The required task for the robotic arm requires only two degrees of freedom*; one along the XY-plane rotational around the Z-axis, and one in the YZ-plane rotational around the X-axis. We designed our robotic arm to accomplish this with an optimal/idealrange of motion around both axes.Once the gripper has picked up a tire, the robotic arm has the capacity to place the tire in the same orientation or rotated 180 degrees, and also allowstires of identical size to be stacked one on top of each other at the output location

*Although the gripper moves in the X or Y direction (depending on which input/output is being serviced) while opening/closing, it can be simply regarded as open or closed.

A rotation of 180 degrees is possible in the YZ-plane around the X-axis in order to flip the tires over 180 degrees

A rotation of 360+ degrees is possible around the Z-axis in the XY-plan in order to service all 3 input and 1 output location(s)

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Differential gear system & work gears

The use of a differential gear system allows the motion from the motor to not only produce a differential in speed along its axis, but it also provides a secondary rotation when the axial rotation is unable to continue. Once the grippers have closed on a tire, the worm gear locks the gripper closed as well as stops rotation of the central shaft. Due to the internal gear structure of the differential, the outer casing of the differential, which acts as a gear, rotates when the central shaft locks. This complicated mechanism makes one motor capable of two functions that require rotation, closing the grippers then rotating the arm about the X-axis.

Separate worm-gear systems are used on either end of the differential system to drive the gripping and flipping of the tire. This is to lock each sub mechanism in place when the worm gear is not being driven. The gear interactions can be best viewed below.

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Stationary base

The base of the robot is fixed in the ground to greatly increase stability and load capacity. This allows full motion to take place at ground level without any issues of clearance. Since the base constrains the rest of the robotic arm, it is required that it be stable and not affect the movement of the rest of the arm. For this reason, we placed the base and the motor controlling the rotation around the Z-axis just below the surface of the ground. This will require a pit to be prepared before installation.

Touch Sensors and Timing:

The motion of the robotic arm is limited and controlled by timing the voltage applied to the motors as well as touch sensors to detect the position of the arm. When initialized, the robotic arm will move into position opposite the output conveyor (input 2), which has a touch sensor that signals the motor to stop. The arm will then either pick up a tire at this position by closing the grippers, or rotate about the X-axis to flip the tire over to the output location. The required timing and application of voltage to the motor for each respective task has been calculated and programmed in to the controller. When the arm has a tire within the gripper, it then rotates around the Z-axis back to input2 using timed rotation, and then rotates around the X-axis 180 degrees until it contacts a second touch sensor. When the second touch sensor is triggered, the gripper motor is signalled to open and release the tire. This system provides the arm with the ability to adapt to different conveyor positions, different numbers of conveyors, and with the possibility of a different output position.

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Lego Mindstorm Program:

Lego mindstorm program to pick up the tire twice from all conveyor belts, speed of the motor B has been adjusted according to angle we need, and timing has been set to pick up the tire from side conveyor belts.

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FEM Report and Images:Loads

Step NameNumber of

referenced loadsLoads

Subcase - Static Loads 1

1

Pressure(1) TypePressure - Normal pressure on 2D elements or 3D element faces

Solver Card Name

PLOAD4

Layer 1

Applied to 18 Polygon Face

Description

Pressure 9607.73 N/mm^2(MPa)

Method Constant

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Constraints

Step Name Number of referenced constraints Constraints

Subcase - Static Loads 1 2

Fixed(1) Type Fixed - Fixed

Solver Card Name SPC

Layer 1

Applied to 1 Polygon Face

Description

Fixed(2) Type Fixed - Fixed

Solver Card Name SPC

Layer 1

Applied to 1 Polygon Face

Description

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Structural Results

Coordinate System : Absolute RectangularNumber of load cases : 1

Subcase - Static Loads 1 : Number of Iterations = 1

Displacement (mm) Stress (mN/mm^2(kPa))

X Y ZMagnitu

deVon-

MisesMin

PrincipalMax

PrincipalMax

Shear

Static Step 1

Max

1.563e+004

5.467e+003

4.192e+002

1.650e+004

6.248e+008

1.017e+008

7.231e+008

3.351e+008

Min

-2.317e+0

02

-9.775e+0

02

-1.825e+0

03

0.000e+000

4.146e+003

-7.714e+0

08

-1.938e+0

08

2.384e+003

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ImagesStress:

Displacement:

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Maintenance Guide

WARNING: All energy sources MUST be tagged AND locked out before any maintenance.

Pre-Production: Before running the machine for full time production for the first time, it is important to run the pre-programmed break in cycle once or twice. This program runs a gentle cycle that lightly works in the gears to avoid the damages that can occur when running the system at full capacity immediately after assembly.

On a daily basis, the pre-production diagnostic program should be run. This is a program that assesses the state of the system by moving the arm in a variety of motions. There are also a variety of maintenance functions that hold the assembly in a certain position then lock in place. This allows for easy accessibility to inner components. Once these programs have run, the machine MUST be locked out and tagged.

Production Maintenance: All gears and axles need to be lubricated every 4-6 months to preserve longevity of product life as well as ensure optimal performance.

The differential gear system wears faster than the regular gears, and the worm gears wear even faster than that. These parts should be routinely expecting biannually, and will usually need to be replaced on a 10 year maintenance schedule.

Many joints are under extreme levels of stress and need to be inspected daily for strain and signs of degradation. Under ideal conditions, the joints in the jaw assembly should be placed in a 2 year maintenance replace cycle, however, diligence is required upon inspection to report and/or replace in case of degradation.

The base contains ball bearings, which require daily inspection and frequent lubrication. The bearings should be placed on a 2 year maintenance replace cycle.

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Bibliography

Machine Design; Apr 17, 1997; 69, 8; ProQuest Science Journals. pg. 132

AMSoil. Advertisement. AMSOIL Synthetic Motor Oil Diesel Motorcycle Engine Transmission. Web. 28 Nov. 2011. <http://www.1st-in-synthetics.com/change_gear_lube_after_break_in_period_for_long_differential_life.htm>.

Explanation of break in period and importance of lubrication to prevent differential wear

Espacenet - Home Page. Patent Archive. Web. 25 Nov. 2011. <http://worldwide.espacenet.com/>.Used to research existing patents on similar products

"Arms E- Robotics Technology." Electronic Tutorials, Electronic Kits, Electronic Tutorials,Electronic Hobby Kits, News. Electronicsteacher.com. Web. 30 Nov. 2011. <http://www.electronicsteacher.com/robotics/robotics-technology/arms.php>.

Used to gain information on typical industrial robotic armsWilcher, Don. Lego Mindstorms Mechatronics. Google Books. Web. 23 Oct. 2011.

<http://books.google.ca/books?id=iTvKboAoT5sC>.

Used to learn about programming the controller"Engineering and Applications Factor of Safety Review." Engineersedge.com. Web. 26 Nov. 2011.

"Differential Gear System." Gears. Web. 27 Nov. 2011. <http://www.gearinfo.com/Differential-Gear-System.html>.

Used to learn about how to use differential gear systems

"SCIENCE :: PHYSICS: MECHANICS :: GEARING SYSTEMS :: WORM GEAR Image." Visual Dictionary Online. Web. 25 Nov. 2011. <http://visual.merriam-webster.com/science/physics-mechanics/gearing-systems/worm-gear.php>.

Information on how to use a worm gear

Thibault, Ray. "The Ins and Outs of Worm Gears." Machinerylubrication.com. May-June 2001. Web. 28 Nov. 2011.

More information on worm gears

"How Industrial Robot Is Made - Material, History, Used, Parts, Components, Industry, Machine, History, Raw Materials, The Manufacturing Process of Industrial Robot, Quality Control, The Future." How Products Are Made. Web. 29 Nov. 2011. <http://www.madehow.com/Volume-2/Industrial-Robot.html>.

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Details on common industrial robots

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