Selfbalancing Handsfree InterFunctional Transport S'H'I'F'T'

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Self-balancing Hands-freeInter-Functional
Transport (S.H.I.F.T.)

• Team MEM-11
• Robert Ellenberg MEM/ECE
• Andrew Moran MEM
• John Spetrino MEM
• Advisor Dr. Paul Oh
• MEM Department
• May 30th, 2007

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Problem

• Humanoid Mobility
• Slow and Inefficient
• Power Consuming
• Wear and Tear
• To our knowledge, an enabler does not exist that
  both Humans and Humanoids can use.

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Thresholds and Objectives
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Existing

• Segway PT i2
• nBot
• Zappy
• Tank Chair
• John Deere Gator
• Chrysler GEM
• B.E.A.R. (Battlefield ExtractionAnd Retrieval
  Robot)
• Electric Unicycle
• Home-made Segway

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GAP between Existing and Required

• Nothing exists that is Hands Free
• Single-Link vs. Multi-Link Pendulum
• Labor Intensive riding
• Unstable
• 1 wheeled Low speed turns/idle
• 3 wheeled High speed turns
• Small scale
• Can not physically carry humans, heavy loads or
  push/pull 20lbs.
• Not designed for Human riders
• Specifically for Robot Experimentation

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Background

• INSERT Sr_Design_Video_3.mpg

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Major Design Decisions

• 2 Parallel wheels
• Air-filled tires
• Adjustable foot controls
• Off the shelf parts
• Electrically Powered
• Gear Drive
• Sensor Suite Encoders / IMU / DSP

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System Dynamics

• Multi-link inverted pendulum
• No practical way to measure link angles
• Changing centers of mass
• Difficult control problem
• Lessons Learned
• Know how to model single-link inverted pendulum
• Design to reduce body movement

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Single Link Approximation

• Model coordinates
• f Pitch angle
• ? Wheel angle
• a Ground incline

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MATLAB Simulation for Component Requirements

• Simulation conditions
• Steady acceleration at 1m/s2 from t0 to t2.25
• 8 incline from t6..10
• Steady state velocity of 4 m/s
• Results
• Smooth, stable operation
• Voltage signal oscillation, can be filtered in
  software
• Found peak current/voltage requirements

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MATLAB Simulation for Battery/Motor Requirements

• Battery Simulation conditions
• Energy Avg. Torque Total Wheel Rotation
• Calculated minimum battery capacity 200 VAhr at
  4mph
• Design battery capacity of 550 VAhr
• Current Requirement 30A
• Peak Current 120A
• Motor Simulation
• Incline Torque 220 oz.-in.
• Motor Speed 4000rpm
• Peak current 60A

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Power System Components

• Magmotor Inc.S28-400-E4
• 200 oz-in continuous Torque
• 1700 oz-in peak Torque
• 10.54 krpm/V
• Thunderpower Li-Poly batteries
• 3.85 A-hr / cell
• 48V (11V37V)
• 22C continuous current capacity

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Open Source Motor Controller (OSMC)

• Low price (200/unit)
• Low on-resistance
• Analog PWM Input
• Manufacturer Rating
• 13-50 VDC
• 160A Continuous
• 400A Surge Current

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Sparkfun IMU

• 6DOF ADXRS Gyro
• Pitch rate of 150 deg/s
• 10 bit data resolution
• Low price 359
• DSP capable of running simple filtering/calibratio
  n algorithms
• Accelerometers to measurestatic angle

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Processor

• Texas Instruments F2812 DSP
• Processing Power
• Multiple Peripheral Interfaces (QEP, SCI, ADC,
  PWM)
• Floating Point Processing
• Programmable in C/C
• Extensive code base
• In house knowledge

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Mechanical Design

• Minimized moments of inertia
• 3 DOF Adjustable User Interface
• Drive shaft alignment 0.002
• Dowel pins for precise alignment
• Battery isolation
• Accessible electrical components.

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Mechanical Design
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Mechanical DesignFinite Element Analysis

• Aluminum Chassis
• Ease of machining
• Easy to hold tolerances
• Lightweight
• FEA
• Shaft bending and shear load

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Manufacturing and Testing
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Manufacturing and Assembly

• Machining and Assembly
• Over 100 shop hours per team members
• Extra time required for tight tolerances
• Shaft and drivetrain tolerances /- .002
• Lessons learned
• Underestimated machining time
• Limited access to precision tools
• Limited manpower

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Lessons Learned OSMC

• OSMC did not perform as specified by manufacturer
• Official Rating 50VDC max
• Actual Rating 36VDC max
• Lacked Over-voltage Protection
• Lessons Learned
• Proper over-voltage protection
• Emergency motor disconnect
• Voltage safety margin
• Reputable manufacturer

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Lessons Learned Electrical Power System

• Separate motor relay/switch
• Separate motor and battery overcurrent protection
• Battery quick disconnect
• Wire harness for battery tray

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Lessons Learned Sparkfun IMU

• Sparkfun IMU
• Required extensive characterization
• Damaged during initial testing
• Lessons learned
• IMU data processing exceeded project scope
• Reliability of manufacturer

• DMU 300

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Timeline
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Thresholds and ObjectivesAchieved
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Thresholds and ObjectivesAchieved
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Economic Analysis
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The Next Steps

• Optimize Balancing
• Improve sensor feedback
• Improve Data processing
• Achieve Top Speed
• Robust 48V motor drivers
• Additional safety measures
• Endurance
• Eliminate testing casters
• Use full battery loadout
• Travel to KAIST to study in Humanoid Robotics
  lab

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Societal Impact

• Users
• Reduced fatigue
• Improved mobility
• User becomes less active
• Peers
• Slight risk of collision/injury
• Society
• Enabling device that will allow humanoids to play
  more crucial role

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Environmental Impact

• Costs of Production and Disposal
• Motor
• Batteries
• Electronics
• Operation
• Generation of electricity and associated
  emissions (CO / NOx / SOx)

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Deliverables

• S.H.I.F.T. Prototype
• Source Code
• Design drawings and wire layouts
• Associated research documentation
• Motor Specifications, QFD analysis, etc.

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Acknowledgements

• Dr. Paul Oh
• Dr. B.C. Chang
• DASL Students
• Ellenberg Family
• MEM Department

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QUESTIONS ?
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Motors

• Magmotor Inc.S28-400-E4Servomotor
• Low terminal resistance/inductance
• Light weight (6 lb)
• 42 commutator bars
• Rotor winding for 48V supply
• NEMA 34 Mount

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Gearboxes and Drivetrain

• Danaher MotionNEMA-True 34 (NT34-010)
• 13 arc. Min precision
• 93 efficient
• 700 in.-lbs. output Torque
• Common 101 Ratio
• largest reduction without 2nd stage
• Bolt directly to S28-400-E4
• 530 each

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Gearboxes and Drivetrain cont.

• 3/4 Belts and Pulleys to act as clutch.
• Protect motor
• Isolates external loads from motor and gearbox
• Change gear ratios cheaply and easily.
• 1.441 pulley ratio gives final drive ratio
  14.41
• Max speed of about 15mph

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Tires and Wheels

• Kevlar Belted Tires
• Skyway Mags
• 20 Utility Configuration
• ¾ Hub 3/16 Keyway
• Discounted to 30 Shipping
• No Non-Disclosure Agreement
• Lightweight
• 3lbs vs. 12-14lbs.

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Processor

• Texas Instruments F2812 DSP
• Complete development package
• Programmable in C/C
• Extensive code base
• In house knowledge

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IMU

• Sparkfun IMU, 6DOF ADXRS Gyro
• Pitch rate of 150 deg/s sufficient
• 10 bit data resolution sufficient
• Low price 359
• DSP capable of running simple filtering/calibratio
  n algorithms

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Optical Encoders

• Grayhill 63R256
• Small form factor
• Sufficient angular resolution
• Best performance/
• Best response

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Motor Drivers

• Open Source Motor Controller (OSMC)
• Low price (200/unit)
• Simple, robust, H-Bridge
• Low on-resistance
• Compatible w/ DSP PWM output

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Project Risk Items - High
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Project Risk Items - Medium
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Project Risk Items - Low
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Software Development

• Reading sensors
• Encoders (QEP)
• IMU (Serial)
• Analog input and gain adjustment
• Calculate states
• Apply gains/negative feedback
• Generate PWM waveform

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Original Economic Analysis

• Should we delete this?