Collisionless Rimless Wheel (Wired) P13211Week 9 Detailed Design Review

Meeting Purpose1. Review project details and engineering “numbers”2. Review of energy calculations3. Review of all part analyses3. Review of Bill of Materials Review Topics1. Project description2. System structure3. Energy Calculations4. Chosen Design5. Chosen Materials6. Bill of Materials

Meeting Date: November 2nd, 2012 Meeting Time: 12 noon - 2:00pm Meeting Location: 09-2130 Proposed Agenda:

Start Time

Topic Required Attendees

12:00 Project description, goals, and deliverables

Dr. Gomes, Dr. Slack, Dr. Hanzlik

12:10 System Structure Dr. Gomes, Dr. Slack, Dr. Hanzlik

12:20 Energy Calculations Dr. Gomes, Dr. Slack, Dr. Hanzlik

12:40 Chosen Design Dr. Gomes, Dr. Slack, Dr. Hanzlik

1:05 Chosen Materials Dr. Gomes, Dr. Slack, Dr. Hanzlik

1:25 Bill of Materials Dr. Gomes, Dr. Slack, Dr. Hanzlik

1:45 Questions/Clarifications Dr. Gomes, Dr. Slack, Dr. Hanzlik

Team Members

Name Role

Owen Accas Mechanical Engineer

Daniel Crossen Mechanical Engineer

Madeline Liccione Electrical Engineer

Rebecca Irwin Electrical Engineer

Hao Shi Mechanical Engineer

Project Motivation & BackgroundAs robots become more and more integrated into our daily lives, the energy consumption has become a critical issue for robotic design. Energy efficiency for robotic walkers has garnered much research attention from the robotics community. Cost of transport (CoT) is usually used as a measure for locomotion energy efficiency, and is defined as energy used/(weight moved x distance travelled). The rimless wheel is very promising as a candidate for low cost-of-transport robotic transportation. Previous research efforts at RIT’s Department of Mechanical Engineering have led to a prototype rimless wheel that can walk down an 8 degree incline without an external power source. Project StatementThe goal is to design, build, and test a rimless wheel that is capable of walking at least 25 steps across level ground with minimal energy consumption while collecting data of the dynamics of the motion. Objectives1. Design and build a rimless wheel that can walk at least 25 steps across level ground2. Achieve at least 40 trials with 25 steps per trial3. Record and analyze relevant dynamical variables as functions of time4. Record and archive videos of successful trials5. Achieve CoT of 0.1 or less Deliverables1. A rimless wheel that can walk at least 25 steps across level ground2. Data collected on the angular motion and position of the inertia wheel and rimless wheel3. Videos of successful trials4. User manual Assumptions & Constraints1. Assume all materials we choose are available to us (will investigate post SDR)

2. Assume lead times for custom parts will be less than the length of MSD II (will investigate post SDR)3. Size, weight, and exotic materials must be constrained4. Power usage should be constrained5. Cost should be less than $900, ideally less than $800 Issues & Risks1. Material lead times and manufacturability2. Material flaws3. Effectiveness of actuation4. Technical errors Expectations for Detailed Design Review1. Assessment of the feasibility of our proposed system2. Mutual understanding between the customer, the project guides, and the team about the objectives and deliverables of the project3. Obtain critical feedback on our performance as of this review Customer Needs While the PRP gave an initial list of 9 customer needs, we scheduled a meeting with Dr. Gomes in order to get a better list, and to hear exactly what he wanted, with no solutions attached. We came up with the following list of 11 customer needs:

Customer Needs Number Importance

Detail

CN1 1 Collect data to prove periodic motion across level ground

CN2 2 Collect current/voltage of battery

CN3 1 Record angular velocity of the spokes and wheel (theta_dot)

CN4 1 Record angle between the two (theta_relative)

CN5 2 Record current/voltage to actuators

CN6 1 Have periodic motion

CN7 1 25 steps ('infinite' walking distance)

CN8 2 Resolution needs: aim for 100 Hz

CN9 1 Reduce energy loss (both electrical and mechanical)

CN10 1 Be portable

CN11 1 Aiming for .05 or .1 Cost of Transport

CN12 2 Be rigid

Engineering Specification

Function Specifications (metric)

Unit of Measure

Marginal Value

Ideal Value Customer Needs

Satisfied

Owner

S1 System Largest dimensions

m ≤ 1.5 ≤ unpowered prototype

CN10 Owen

S2 System Weight Lbs ≤ 20 ≤ 5 CN9, CN10 All

S3 System System cost $ < 900 < 800 CN9 All

S4 System Number of steps

Integer ≥ 20 >=25 CN6, CN7 Maddie

S5 System Resolution of angular velocity

data

deg/sec 1 ≥ 0.1 CN1, CN3, CN8

Becky

S6 System Resolution of angular position

data

deg/sec 0.5 ≥ 0.1 CN1, CN4, CN8

Becky

S7 System Total cost of transport of

device

Unitless 0.1 0.01 CN9, CN10, CN11, CN12

All

S8 System Data sampling rate

Hz ≥ 100 ≥ 500 CN1, CN2, CN3, CN4, CN5, CN8

Maddie

S9 System Operational time between charges for

system

Hours 0.5 1.5 CN9 Becky

S10

System Amount of data for onboard

storage

Hours 0.1 0.5 CN1, CN2, CN3, CN4,

CN5

Maddie

S11

System Safe for user and observers

Binary Yes Yes CN12 All

S22

System Number of 25 step trials achieved

Integer ≥ 40 ≥ 50 CN6, CN7 All

S23

System Training time (1st time)

Hrs 0 <0.5 CN1 All

Proposed Design1. Frame material

● Carbon fiber plates● Thin walled steel braces● aluminum axle

2. Number of spokes/points of contact per side● Decided on 5 for ease of comparison with current prototype● 4 seemed like the most challenging/desirable number, but analyses done by previous

students indicates that the amount of force needed to actuate the system may be too large to surmount

3. Actuation Mechanism● String drive (strings wrapped around motor)● Rotating axle rigidly connected to the bike wheel

4. Data Processing and Control● TI microprocessor + custom controls work○ Complete control over motor control system; best way to ensure optimal power consumption○ May be too difficult and time-consuming to program and configure from scratch● TI modular motor control kit○ Will not have to program a microcontroller from scratch○ Can simply plug in a microcontroller card; all of the motor driving and problems (back emf, optical isolation, etc.) are taken care of○ Different kits for different types of motors○ Biggest drawbacks are large size, nonuniformly distributed mass and high cost● Gyrosensors are most viable option for relative angle and angular velocity measuring

5. Slippage Reduction● High friction feet (using PC non-slip pads)

Detailed Block Diagram

Proposed Design CAD Drawing Description● 2, pentagon-shaped carbon fiber plates● 5 Thin-walled steel supports at the ends of each of the points● Aluminum mounting plates to mount the axle to the fiber glass plates● similar string/spring set up as prototype, but the string is now attached to motors inside the axle● 2-part axle: smaller diameter axle to hold the bike wheel bearing-connected to the larger one to hold the motor● motor inside the axle on one side of the bike wheel, meant to add torque to the bike wheel through the axle, which is connected to the frame by bearings● batteries mounted on outside of bike wheel for increased inertia (modeled currently as 9V batteries, but will most likely go with a better alternative)● all connections between plates will be hollow for installing wires, excluding the middle axle● We will be adding high friction feet/pads onto the end of each of the pointsIncreased surface area provided by plates gives more area for electronics (electronics currently not modeled on cad drawing● Plastic Inserts inside foam so as to not crush the foam when tightening fasteners

Proposed Design CAD Drawings

Proposed Design Schematics and Component Specific Block DiagramsCustom schematics are still being finalized and will be presented at the time of the review.

Closed loop with feedback sensor motor control system that is the basis for each control system. The feedback sensor will likely be an encoder packaged with the motor.

TI LaunchPad Microcontroller Development Platform, Page 1

TI LaunchPad Microcontroller Development Platform, Page 2

Block diagram of internal workings of L3GD20 3-axis gyroscope

Very basic motion control algorithm not including the clutch system

Bill of Materials (previous design)

Already ordered/Already have obtainedReady to order/Know where we are ordering fromDo not know where we are ordering from/Do not know what we need (not good condition)

Bill of Materials (new design)

Already ordered/Already have obtainedReady to order/Know where we are ordering fromDo not know where we are ordering from/Do not know what we need (not good condition)

(Hand out will be provided with larger font)