Motion Control: Generating Intelligent Commands for Mechatronic Devices Kelvin Peng January 31 st 2013

What is Control? Getting the System to do What you Want

How to Control? Pros: Eliminates errors Disturbance rejection Cons: Stability? Sensors Controls 101: Add a Feedback Loop!

Let’s go back to simple control Today’s topic: How to design the command generator for oscillatory plants Pros: Simple, no sensors Stable (if plant is stable) Accurate model not needed Cons: No disturbance rejection Increase rise time

Bridge Crane Vibration Problem

(and solution)

Why is Vibration Cancelled? t1t1 t2t2

Solving for the two impulses Vibration Amplitude (after n impulses) Normalization Positive Impulses Time Optimality t1t1 t2t2 We want this to be zero, i.e. V=0

Solving for the two Impulses 3 equations, 3 unknowns Zero-Vibration (ZV) input shaper

Input Shaping Arbitrary Commands Slight increase in rise time ΣA i = 1 so that shaped and initial commands have same steady state

Bridge Crane Vibration Problem

Typical Responses

Implementing a Digital Input Shaper Unshaped Command Shaped Command

Shaper Robustness Insensitivity – the width of a sensitivity curve where vibration remains under V tol, the tolerable level of vibration

Increasing Shaper Robustness Insensitivity – the width of a sensitivity curve where vibration remains under V tol, the tolerable level of vibration

Increasing Shaper Robustness Extra Insensitive (EI) Shaper Insensitivity – the width of a sensitivity curve where vibration remains under V tol, the tolerable level of vibration

Increasing Shaper Robustness Like a Boss Tradeoff: More impulses are needed, and therefore slower rise time.

Multi-Mode Input Shaping Design a shaper for each mode, then convolve to get a shaper that eliminates both modes

ZV Shaper for 1 Hz ZV Shaper for 2 Hz X ZV Shaper for 1 Hz and 2 Hz

Multi-Mode Specified Insensitivity (SI) Shaper

Shaping for Double-Pendulum Payloads

Shapers with Negative Impulses Unity Magnitude UMZV shaper Negative shapers: Faster But less robust May excite un- modeled higher modes

Special Case: Negative Shapers for On-Off Actuators Not On/Off UMZV Shaper: On-Off

On-Off Thrusters: Flexible Satellites (Tokyo Institute of Technology)

On-Off Thrusters: Flexible Satellites (Tokyo Institute of Technology)

Input Shaping With Feedback Control Input Shaper * Cascaded set of 2 nd order systems Collapse the feedback loop

Input Shaping and Feedback Control: Experimental Data Disturbance at EndDisturbance During Motion

Input Shaping Inside the Feedback Loop: Hand-Motion Crane Control

RF Hand-Motion Crane Control

Human Operator Studies

Human Operator Learning

UnshapedShaped

Portable Tower Crane 2mx2mx340 o Interfaces: Pendent, GUI, Internet GUI Overhead Camera Used by Researchers and Students in Atlanta, Japan, Korea

Tower Crane: System Overview Screen Interface

ME6404 Class Contest

Other Applications Many types of cranes Milling machines Coordinate measuring machines Disk drives Long reach robots Spacecraft

Multi-Hoist Cranes

Multi-Axis Input Shaping

Scale of Micro Meters (10 -6 m) High Spindle Speeds (120 kRPM) Application of Command Shaping to Micro Mills

Experimental Results Stage Tracking Error Part Surface

Coordinate Measuring Machines

Coordinate Measuring Machine (CMM) Deflection

Disk Drive Head Tester

Painting Robot

GRYPHON Mine Detecting Robot

Every control method has strengths and weaknesses (Feedback is not a magic cure-all) The command issued to a system has a significant influence on its response Input shaping  Is excellent for applications with problematic vibrations  Is easy to implement Conclusions

Thank you

Before we go on… A General Control System