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Research Papers

Negative Input Shaping: Eliminating Overcurrenting and Maximizing the Command Space

[+] Author and Article Information
Khalid L. Sorensen

Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332sorensen@gatech.edu

Aayush Daftari

Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332

William E. Singhose

Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332singhose@gatech.edu

Keith Hekman1

Department of Engineering, Calvin College, Grand Rapids, MI 49546

The crane simulation utility may be downloaded freely from http://singhose.marc.gatech.edu/cranewebpage/CraneSimulationForCommandSpace.zip

It should be noted that this measurement differs fundamentally from average residual angular displacement. Residual oscillation refers to payload sway exhibited after a command has reached a steady-state value. Total oscillation includes payload sway during transient and steady-state portions of a command.

1

Present address: School of Engineering, California Baptist University, Riverside, CA 92504; electronic mail: khekman@calbaptist.edu

J. Dyn. Sys., Meas., Control 130(6), 061012 (Oct 10, 2008) (7 pages) doi:10.1115/1.2957646 History: Received October 12, 2007; Revised May 11, 2008; Published October 10, 2008

Input shaping is a filtering method used for reducing oscillation in flexible systems. A class of these filters, called negative input shapers, has been developed to improve system rise-time beyond what is achievable using conventional input-shaping filters. However, negative input shapers can cause overcurrenting and subsequent system oscillation, when used with certain reference commands. This class of reference commands is examined in the context of the command space. The command space represents the space of all possible signals that may be issued to a system. It provides insight into how overcurrenting occurs, how overcurrenting can be mitigated, and the influence that mitigation strategies have on system performance. Two overcurrenting mitigation strategies are presented. The operational effects of overcurrenting and overcurrenting mitigation are evaluated using a three-dimensional simulation of a bridge crane, and experimental results from a 10ton industrial bridge crane.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 7

Current and past values of x(t) comprising the coordinate of a point in the command space

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Figure 8

Saturated and drivable regions for a UM-ZV input shaper

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Figure 9

Mitigation of overcurrenting using the state transition constraint

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Figure 1

Shaped command (solid); payload response (dashed)

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Figure 2

Shaped command with overcurrenting (solid); payload response (dashed)

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Figure 3

Input-shaping block diagram

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Figure 4

ZV and UM-ZV input shapers for a system with zero damping. T is equal to the period of oscillation.

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Figure 5

Limited actuation block diagram with input shaping

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Figure 6

Command space for a three-impulse input shaper

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Figure 10

Transition constraint represented as two planes in the drivable region of the command space

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Figure 11

Mitigation of overcurrenting using the variable saturation constraint

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Figure 12

Experimental test-beds for crane operator experiments

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Figure 13

Experimental performance results

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