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Research Papers

Characterization and Attenuation of Sandwiched Deadband Problem Using Describing Function Analysis and Application to Electrohydraulic Systems Controlled by Closed-Center Valves

[+] Author and Article Information
Song Liu

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

Bin Yao1

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907byao@purdue.edu

In backstepping design, loosely speaking, each ki represents the converging rate of the closed-loop dynamics in the corresponding step. By making them all have the same value, one can make various loops have the same converging rate. This is different from the conventional design where the inner loop is required to have much higher converging rate or bandwidth than the outer loop.

1

Corresponding author. Also a Kuang-piu Professor at the State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, China.

J. Dyn. Sys., Meas., Control 131(3), 031002 (Mar 19, 2009) (7 pages) doi:10.1115/1.3089557 History: Received April 04, 2005; Revised December 31, 2008; Published March 19, 2009

Unlike input deadband, the sandwiched deadband between actuator and plant dynamics is very difficult to be explicitly compensated for due to the proceeding actuator dynamics whose effect may not be negligible. The paper presents a practical way to overcome the design conservativeness of existing methods in dealing with sandwiched deadband. Specifically, a describing function based nonlinear analysis method is proposed to characterize the effect of the sandwiched deadband on the stability and performance of the overall closed-loop system. The analysis results can be used to determine the highest closed-loop bandwidth that can be achieved without inducing residual limit cycles and instability. Optimal controller parameters can then be found to maximize the achievable closed-loop control performance. The technique is applied to an electrohydraulic system controlled by closed-center valves and a nonlinear feedback controller. Simulation results showed severe oscillations as the feedback control gains are increased to the predicted threshold values. Comparative experimental results also showed the effectiveness of the proposed method in reducing the conservativeness of traditional design and the improved closed-loop control performance in implementation.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Direct compensation of sandwiched deadband

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Figure 2

Feed-forward control of sandwiched deadband

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Figure 3

Feedback control of sandwiched deadband

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Figure 4

Overlapped spool of a closed-center valve

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Figure 5

Simulation results for different K value

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Figure 6

Comparative experiment results

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