A method of robotic actuation using control moment gyros
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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

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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


Questions

Questions?


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