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Self-balancing Hands-free Inter-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 30 th , 2007 Problem Humanoid Mobility Slow and Inefficient Power Consuming Wear and Tear

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self balancing hands free inter functional transport s h i f t

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

slide2

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.
slide4

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
gap between existing and required
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 20+lbs.

Not designed for Human riders

Specifically for Robot Experimentation

slide6

Background

  • INSERT Sr_Design_Video_3.mpg
major design decisions
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

system dynamics
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

slide9

Model coordinates

φ: Pitch angle

θ: Wheel angle

α: Ground incline

Single Link Approximation

slide10

MATLAB Simulation for Component Requirements

Simulation conditions

  • Steady acceleration at 1m/s^2 from t=0 to t=2.25
  • 8° incline from t=6..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
slide11

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
slide12

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 (11V+37V)

22C continuous current capacity

Power System Components

slide13

Low price ($200/unit)

Low on-resistance

Analog PWM Input

Manufacturer Rating:

13-50 VDC

160A Continuous

400A Surge Current

Open Source Motor Controller (OSMC)

slide14

Sparkfun IMU

  • 6DOF ADXRS Gyro
    • Pitch rate of 150 deg/s
    • 10 bit data resolution
    • Low price $359
    • DSP capable of running simple filtering/calibration algorithms
    • Accelerometers to measurestatic angle
slide15

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
slide16

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.
slide19

Mechanical DesignFinite Element Analysis

  • Aluminum Chassis
    • Ease of machining
    • Easy to hold tolerances
    • Lightweight
  • FEA
    • Shaft bending and shear load
manufacturing and assembly
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
slide22

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
lessons learned electrical power system
Lessons Learned: Electrical Power System
  • Separate motor relay/switch
  • Separate motor and battery overcurrent protection
  • Battery quick disconnect
  • Wire harness for battery tray
slide24

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

the next steps
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
societal impact
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
environmental impact
Environmental Impact
  • Costs of Production and Disposal
    • Motor
    • Batteries
    • Electronics
  • Operation
    • Generation of electricity and associated emissions (CO / NOx / SOx)
deliverables
Deliverables
  • S.H.I.F.T. Prototype
  • Source Code
  • Design drawings and wire layouts
  • Associated research documentation
    • Motor Specifications, QFD analysis, etc.
acknowledgements
Acknowledgements

Dr. Paul Oh

Dr. B.C. Chang

DASL Students

Ellenberg Family

MEM Department

slide36

Magmotor Inc.S28-400-E4Servomotor

Low terminal resistance/inductance

Light weight (~6 lb)

42 commutator bars

Rotor winding for 48V supply

NEMA 34 Mount

Motors

slide37

Gearboxes and Drivetrain

  • Danaher MotionNEMA-True 34 (NT34-010)
  • 13 arc. Min precision
  • 93% efficient
  • 700 in.-lbs. output Torque
  • Common 10:1 Ratio
    • largest reduction without 2nd stage
  • Bolt directly to S28-400-E4
  • $530 each
slide38

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.
    • 1.44:1 pulley ratio gives final drive ratio 14.4:1
    • Max speed of about 15mph
slide39

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.
slide40

Processor

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

40

slide41

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/calibration algorithms
slide42

Optical Encoders

  • Grayhill 63R256
    • Small form factor
    • Sufficient angular resolution
    • Best performance/$
    • Best response
slide43

Open Source Motor Controller (OSMC)

Low price ($200/unit)

Simple, robust, H-Bridge

Low on-resistance

Compatible w/ DSP PWM output

Motor Drivers

software development
Software Development
  • Reading sensors:
    • Encoders (QEP)
    • IMU (Serial)
    • Analog input and gain adjustment
  • Calculate states
  • Apply gains/negative feedback
  • Generate PWM waveform
original economic analysis
Original Economic Analysis
  • Should we delete this?