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A Method of Robotic Actuation using Control Moment Gyros. Presenter: Ian Livingston AIAA YPSE ‘08 November, 21 st 2008. Overview. Introduction What is a CMG Reactionless Actuation Joint Torques vs. Body Torques Planar Robot Design Simulation Results

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a method of robotic actuation using control moment gyros

A Method of Robotic Actuation using Control Moment Gyros

Presenter: Ian Livingston

AIAA YPSE ‘08

November, 21st 2008

overview
Overview
  • Introduction
  • What is a CMG
  • Reactionless Actuation
  • Joint Torques vs. Body Torques
  • Planar Robot Design
  • Simulation Results
  • Experimental Design (Functional Flow)
  • Hardware and GUI
  • Controller Design
  • Closed Loop Gimbal Control
  • Feed Forward Joint Angle Control
  • Video
  • Future Plans
  • Acknowledgements
  • Questions

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

control moment gyros cmgs
Control Moment Gyros (CMGs)
  • Components:
    • Constant speed reaction wheel
    • Gimbal motor (positioned along g axis)
  • Applications:
    • Momentum Storage
    • Propellant-less Attitude Control
  • Advantages:
    • Low Power (100x)1
    • Spaceflight heritage

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Equation for torque output

Equation for reaction wheel momentum

hr = Irw·wrw

1. Carpenter, Peck 2008

reactionless actuation
Reactionless Actuation
  • Reaction Forces from Mechanism
  • Actuator Reaction Forces
    • Caused by direct-drive motors. To rotate an object the motor rotates the base object in the opposite direction.
  • Inertial Reaction Forces
    • Caused by a spinning object not at the center of mass.
  • Advantages to Reaction-
  • Less Actuation:
  • Isolate subsystems
  • Reduce dumped
  • momentum to the base
  • structure.

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

CMG Arm from previous project team on the “Vomit Comet”

joint torques versus body torques
Joint Torques Versus Body Torques

Joint Torques

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Body Torques

  • CMGs create body torques
  • The motion of the arm remains the same
  • Only the torque caused by the off center reaction force needs to be absorbed using body torques.

tcmg

tmotor

R2

T2

R2

q1

R2

t2 R

q1

R2

t2

planar robot arm design
Planar Robot Arm Design
  • Purpose:
  • To create a CMG robot arm to demonstrate the advantages of body torques on space applications.
  • Design:
  • Two or more link free floating CMG arms
  • Air bearings to provide frictionless surface
  • Use Scissored Pair CMGs to remove
  • Gyroscopic effects and off axis torques
  • Previous work and Motivation:
  • Past teams built the reaction wheels for a CMG arm test
    • Only open-loop results were obtained from zero-g tests
  • This experiment was created to perform tests anytime

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Photo: A. Soto

scissored pair cmgs
Scissored Pair CMGs
  • Advantages:
  • Eliminate off-axis torques
  • Direction of torque is fixed
  • No internal singularities
  • Cancelation of unwanted gyroscopic effects

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Video: M. Peck

simulation analysis and hypothesis 1
Simulation Analysis and Hypothesis1
  • Simulation to determine power properties of CMG arm
  • Utilized several set ups for links and properties
  • Main focus on one link and two link robot arms both in parallel axis and perpendicular joint axes.
  • Simulation assumes 0 initial and final velocities and accelerations.

Joint torque advantage

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

CMG advantage

  • From power simulation results:
  • CMGs are better for reaching tasks
  • Joint torques better for panning tasks

D. Brown, 2008

experimental design functional flow
Experimental Design (Functional Flow)

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

hardware and matlab gui design
Hardware and MATLAB GUI Design

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

controller design
Controller Design

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

  • Gimbal Angle is controlled by a PID closed loop control
  • Joint Angle is controlled using a Simulink model with feed forward control
cl gimbal angle control analysis
CL Gimbal Angle Control Analysis

Equations of motion for gimbal motor:

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Transfer function for gimbal motor:

Root locus, Bode Plots and gains:

Gains:

Kp= 3

Ki = 1

Kd = .1

cl gimbal angle control results
CL Gimbal Angle Control Results

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

feed forward control design
Feed-forward Control Design
  • System is non-linear
  • Small angle approximation was not assumed since f can rotate up to 70°

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

Relationship between Joint angle and gimbal angle:

  • Current issues with Feed-Forward:
  • The runtime of the feed forward Simulink block is approximately .11 seconds.
  • This would limit the control system by 10 data points
  • At maximum voltage this is equivalent to 30 degree rotation
video of cmg robot arm
Video of CMG robot arm

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

future task test and goals
Future task, test, and Goals
  • Current Issues:
    • Joint angle control is not fully functional
    • No support for multi-links
    • Air canisters are currently leaking
  • Planned Tests:
    • Full systems test using feed forward control
    • Evaluation of power consumption versus joint angle control
  • Identified Improvements:
    • Characterize noise in potentiometer and build LQG control
    • Replace existing reaction wheels with smaller and faster COTS wheels
    • Reduce the size of the supporting arm and structure
    • Remove chain and replace with gears

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

acknowledgements
Acknowledgements
  • Daniel Brown, PhD. Candidate, Aerospace
  • Dr. Mason Peck
  • Space Systems Design Studio
  • Cornell CMG team

Outline:

-Introduction

-What is a CMG

-Reactionless Actuation

-Joint Torques vs. Body Torques

-Planar Robot Design

-Simulation Results

-Experimental Design

-Hardware and GUI

-Controller Design

-CL Gimbal Control

-Feed Forward Control

-Video

-Future Plans

-Acknowledgements

-Questions

1. DARPA SUMO spacecraft with CMG arms

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