1kg Motor Module, First Generation

P08208 – Mechanical Design P08205 – Electronics, Controls & Support05.16.08

RP1

MSD II

20073

Team Breakdown

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Subsystems Team 205 Team 208

Drive -- AndrewMatt

Steer Art Matt

Yoke Eric James

Platform ArtEric

--

Controls BrendanPhil

--

Electronics Jonathan Bryan

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WHAT IS A MOTOR MODULE ?

DRIVE

MODULAR MOUNTING

STEER

aka “MM”

1kg

10kg

100kg

OFF THE SHELF MOTOR MODULES

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RP100( Wired ) RP10

( Wired )

Sister projects!

RP10( Redesign )05.16.08

RP1( Wireless )

RP10Redesig

n

Wireless!

Robust!

Autonomous!

Smaller! Lighter!

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FORMATOverview

Project SpecificationsSystem Level

Subsystem Contributions208: Drive / Steer / Yoke205: Support / Electronics / Controls

Closing CommentsResultsStrengths & WeaknessesFuture of RP1

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Steering

Drive Train

Upper Yoke

Lower Yoke

MECHANICAL DESIGN OVERVIEW

Computer

Wireless TransceiversMicroprocessor

PWM Motor Controller

RP1 Motor Module05.16.08

Circuit Board

ELECTRONICS & CONTROLS OVERVIEW

CRITICAL REQUIREMENTS

• Transport 1kg Payload• Robust = Withstand Tabletop Drop• Wireless Communication• Power Motors with a PWM Signal• Open Source & Open Architecture• Reflect Design of the RP Family• Modular Design for Multiple End Uses

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EXPECTATIONSo Quantity

1, Functioning Platform & Motor

Module3, Motor Modules

o Speed @ max efficiency 38 in/s

o Drop Test Repair Time < 20 min

o Battery Life 1 hour +

o Modular Design05.16.08

1 2 3

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• Responsibilities: – Design modular drivetrain system

• Multiple modes of motor operation– Design and build a robust drivetrain

• Challenges of MSD II– Drivetrain friction losses– The need for a belt tensioner?– Machining knowledge inadequacy– Failing drop testing– Unforeseen assembly woes– Differences between analytical solutions and

testing results

Drivetrain Subsystem

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Gearbox Selection Process• Using the chart to the left a

motor gearbox can be selected from velocity requirements that ensures efficient motor operation

Efficiency vs. Velocity

40

45

50

55

60

65

0 20 40 60 80 100 120 140

Velocity (in/s)

Efficiency (%)

5:1

14:1

19:1

27:1

51:1

71:1

100:1

139:1

189:1

• Similarly a motor gearbox can be selected for max motor power

Power vs. Velocity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 20 40 60 80 100

Velocity (in/s)

Power (W)

5:1

14:1

19:1

27:1

51:1

71:1

100:1

139:1

189:1

5:1 REV

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Final Drivetrain Design

IG-32GM 24V Motor

27:1 gearbox reduction

Steel couples with setscrewsStainless steel drive axles

Steel miter gears

Aluminum spacers with thrust bearings1:2 synchronous drive pulleyAluminum axle with keyway for wheel

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Strengths & Weaknesses

• Strengths– Modular gearbox options– Multiple opportunities to change gear ratios– Belt protects critical drive components– Easy assembly of drive components

• Weaknesses– Lack of belt tensioner limits modularity– Size of motor increases RP1 size– Limited availability of motor gearboxes

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• Responsibilities: – Design a steering system capable of infinite

rotation– Implement, build and integrate with all RP1

subsystems

• Challenges of MSD II– Total re-design including custom turntable,

starting week #1• Also incorporated re-vamp of tensioning system

– Subsystem integration– Belt Sizing– Friction!

STEERING SUBSYSTEM

It’s Alive!

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Strengths & Weaknesses• Strengths:

– Robust steer system– Custom turntable is light, smooth, and easy

to access/assemble– Infinite rotation– Intuitive and efficient belt tensioning

• Weaknesses– Side load from belt drive system causing

misalignment– Extreme sensitivity to belt length– Tendency of steer system to force rotation of

drive shaft, and vice versa– Friction!– Demands tight tolerances

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DRIVE & STEERING

Q & A

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YOKE SUBSYSTEM

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Responsibilities: – Responsible for structural skeleton of RP1– Design a rigid and robust framework– House all other sub-systems within framing – Provide protection against a drop to the floor

Challenges of MSD II:– Maintaining machining tolerances during mass

production– Lack of experience with machining equipment

early in MSDII– Developing precise and efficient machining

techniques

YOKE SUBSYSTEM

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Drop Test on Side

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Drop Test on Wheel

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Damage to Axle

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Strengths & Weaknesses

• Strengths– Robust: designed for impact– Concentrates force of impact from drop

in lower axle– Easily assembled and disassembled

• Weaknesses– Size: minimally smaller than RP10– Lower axle fails in drop test but can be

quickly replaced

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• Responsibilities: – Design a prototype platform

• Includes area for 1kg payload• Includes area for platform electronics• Testing the functionality of 1 MM at a time• Built-in wheels to allow for platform travel

– Design a modular mounting system• Must be capable of attachment to platform• Must meet design spec for attachment

• Challenges of MSD II– Use of materials readily available for platform– Having a low center of mass for drivability

PLATFORM

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PLATFORM EFFORTS

Mounting Time:

50 sec

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STRENGTHS & WEAKNESSES

• Strengths– Easy to make prototype platform– Very quick and efficient mounting

• Weaknesses– Made of plywood and boards– Structural support questionable when using

substantial weight– Requires a square-shaped cut-out– MM must mount in the designated forward

direction for index to work properly

YOKE & PLATFORM

Q & A

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• Responsibilities– Provide components for motor control

• H-bridge• Boost & Buck PCB• Interface PCB• Wiring & Connectors

– Design and implement power supply

• Challenges of MSD II– PCB board design– Integration of all electrical components

Electronics

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Electronics

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Electronics

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Printed Circuit Boards

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PCB Build

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• Strengths– Capacity for 2 MM’s– Integration of all electrical components– Single connection with platform

• Weaknesses– Takes time to locate broken components

on PCB– PCB Corrections– PCB has no output diode

Reflections

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• Responsibilities: – GUI for user control– Wireless communication between MM and

computer– Generate all necessary signals used for

controlling motors– Display speed, turning angle, and battery life

• Challenges of MSD II– Selected wireless components not functioning– Limitations of microprocessor – not enough I/O

pins– Out of practice with Java

Controls

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• Wireless Transmission: – Couldn’t download code to MICAZ motes– TelosB motes used instead– Not yet demonstrated to be functional

• Microprocessor:– Freescale – Handles encoder feedback– Speed up, slow down, turn left and right

• GUI:– Java, using the Eclipse IDE– New design in consultation with Prof. Hawker

Implementation

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GUI Screen Shots

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Strengths & Weaknesses

• Strengths– Ability to turn, drive, and stop based on

commands issued by the user– GUI supports multiple platform designs– Open-source, Java readily available

• Weaknesses– One direction communication with the MM– Only set up to work with one MM

CONTROLS & ELECTRONICS

Q & A

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RESULTS

• MM attaches in under 1 minute

• Weighs under 5 pounds

• Complete disassembly in less than 10 minutes

• Compact size• Infinite rotation• Robust• Less than $90005.16.08

COST

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Item Cost

Motor Module Only (2) $809.41

Platform $688.97

2 MMs & Platform $1498.38

Overall Spending $1895.73

THE FUTURE OF RP1

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1 2 3

French Collaboration

with INSA DPM Students Senior

Design for EE & CE’s

Software Engineering

Senior Design

COULD RP1 HANDLE 10Kg?

• Proven robust design• Modular mounting• Replace drive with 1:71 gearbox

motor• Resulting 14.5 in/s @ peak efficiency

• ANSYS MODELING RESULTSCheck:

– Design of Machine Element calculations– Effects on batteries05.16.08

COULD RP1 HANDLE 10Kg?

Yes it can!

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22.5 lb Payload!

(10.2 kg)

REFLECTIONS

Strengths• Robust motor

module• Demonstrated

modular design• Easy to connect• Controllable

turn/drive/stop/align

Weaknesses• Oversized• Failed to implement

wireless communication

• Processor can only handle 1 MM of feedback

• PCB corrections were necessary

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THREE SIMPLIFICATIONS

1. Open motor selection & configuration

2. 170°or 180° rotation requirement, to replace infinite rotation requirement

3. Emphasize compact design + Establish clear size constraints + Goal of existing design size (ex. 10%)

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That’s It Folks!

Q & A

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Gearbox Selection ProcessEfficiency vs. Velocity

40

45

50

55

60

65

0 20 40 60 80 100 120 140

Velocity (in/s)

Efficiency (%)

5:1

14:1

19:1

27:1

51:1

71:1

100:1

139:1

189:1

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Gearbox Selection ProcessPower vs. Velocity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 20 40 60 80 100

Velocity (in/s)

Power (W)

5:1

14:1

19:1

27:1

51:1

71:1

100:1

139:1

189:1

5:1 REV

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ANSYS Simulation

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ANSYS Simulation