Modeling and Multivariable Control Design Methodologies for Hexapod-Based Satellite Vibration Isolation

[+] Author and Article Information
Alok Joshi

Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843-3123, USA

Won-jong Kim

Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843-3123, USAwjkim@tamu.edu

J. Dyn. Sys., Meas., Control 127(4), 700-704 (Nov 30, 2004) (5 pages) doi:10.1115/1.2101842 History: Received March 24, 2003; Revised November 30, 2004

A mathematical model of a six-degree-of-freedom (6-DOF) hexapod system for vibration isolation was derived in the discrete-time domain on the basis of the experimental data obtained from a satellite. Using a Box–Jenkins model structure, the transfer functions between six piezoelectric actuator input voltages and six geophone sensor output voltages were identified empirically. The 6×6 transfer function matrix is symmetric, and its off-diagonal terms indicate the coupling among different input/output channels. Various multi-input multi-output (MIMO) control techniques such as Linear Quadratic Gaussian and H were proposed for active vibration isolation in the broadband up to 100 Hz. The simulation results using these controllers obtain 13 and 8 dB vibration attenuation at 25 and 35 Hz, respectively.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Perspective view of the 6-DOF SUITE hexapod assembly

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Figure 2

Simulated (dashed) and experimental (solid) responses to a 40 Hz sinusoid input signal

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Figure 3

A comparison of the Bode plots of the transfer functions obtained using system identification (dashed—simulation) and with the WGN (solid—experimental)

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Figure 4

Simulated responses of all the six channels of LQG/LTR controller to 25 Hz sinusoid used as the plant input disturbance

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Figure 5

Block diagram for the weight assignment to the control energy u(t) and error e(t) in the H∞ controller design

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Figure 6

Simulated responses of all the six channels of the H∞ controller to a 35 Hz sinusoid used as plant input disturbance



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