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This presentation by Kelvin Peng discusses the fundamentals of control systems for mechatronic devices, focusing on command generation techniques to address oscillatory behavior, particularly in bridge cranes. It contrasts the pros and cons of feedback control and simple control methods, highlighting their effectiveness in eliminating errors and enhancing stability. The presentation explores input shaping techniques, including Zero-Vibration (ZV) shapers, to mitigate vibration issues. It also delves into robust designs and applications across various industries, underscoring the importance of tailored solutions for different mechanical systems.
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Motion Control: Generating Intelligent Commands for Mechatronic Devices Kelvin Peng January 31st 2013
What is Control? Getting the System to do What you Want
How to Control? Controls 101: Add a Feedback Loop! • Pros: • Eliminates errors • Disturbance rejection • Cons: • Stability? • Sensors
Let’s go back to simple control • Pros: • Simple, no sensors • Stable (if plant is stable) • Accurate model not needed • Cons: • No disturbance rejection • Increase rise time Today’s topic: How to design the command generator for oscillatory plants
Bridge Crane Vibration Problem (and solution)
Normalization Positive Impulses Time Optimality Solving for the two impulses Vibration Amplitude (after n impulses) We want this to be zero, i.e. V=0 t1 t2
Solving for the two Impulses 3 equations, 3 unknowns Zero-Vibration (ZV) input shaper
Input Shaping Arbitrary Commands • Slight increase in rise time • ΣAi = 1 so that shaped and initial commands have same steady state
Implementing a Digital Input Shaper Unshaped Command Shaped Command
Shaper Robustness Insensitivity – the width of a sensitivity curve where vibration remains under Vtol , the tolerable level of vibration
Increasing Shaper Robustness Insensitivity – the width of a sensitivity curve where vibration remains under Vtol , the tolerable level of vibration
Increasing Shaper Robustness Extra Insensitive (EI) Shaper Insensitivity – the width of a sensitivity curve where vibration remains under Vtol , 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 and 2 Hz ZV Shaper for 1 Hz X ZV Shaper for 2 Hz
Shapers with Negative Impulses • Negative shapers: • Faster • But less robust • May excite un-modeled higher modes Unity Magnitude UMZV shaper
Special Case: Negative Shapers for On-Off Actuators UMZV Shaper: On-Off Not 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 Collapse the feedback loop Input Shaper * Cascaded set of 2nd order systems
Disturbance During Motion Input Shaping and Feedback Control: Experimental Data Disturbance at End
Input Shaping Inside the Feedback Loop: Hand-Motion Crane Control
Human Operator Learning Unshaped Shaped
Portable Tower Crane • 2mx2mx340o • Interfaces: Pendent, GUI, Internet GUI • Overhead Camera • Used by Researchers and Students in Atlanta, Japan, Korea
Screen Interface Tower Crane: System Overview
Other Applications • Many types of cranes • Milling machines • Coordinate measuring machines • Disk drives • Long reach robots • Spacecraft
Application of Command Shaping to Micro Mills • Scale of Micro Meters (10-6m) • High Spindle Speeds (120 kRPM)
Part Surface Experimental Results Stage Tracking Error
Conclusions • 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
Before we go on… A General Control System