Stability Robustness of LQ and LQG Active Suspensions

[+] Author and Article Information
A. G. Ulsoy

Mechanical Engineering and Applied Mechanics, University of Michigan, Ann Arbor, MI 48109-2125

D. Hrovat, T. Tseng

Scientific Research Laboratories, Ford Motor Company, Dearborn, MI 48202-2053

J. Dyn. Sys., Meas., Control 116(1), 123-131 (Mar 01, 1994) (9 pages) doi:10.1115/1.2900666 History: Received March 14, 1991; Online March 17, 2008


A two-degree-of-freedom quarter-car model is used as the basis for linear quadratic (LQ) and linear quadratic Gaussian (LQG) controller design for an active suspension. The LQ controller results in the best rms performance trade-offs (as defined by the performance index) between ride, handling and packaging requirements. In practice, however, all suspension states are not directly measured, and a Kalman filter can be introduced for state estimation to yield an LQG controller. This paper (i) quantifies the rms performance losses for LQG control as compared to LQ control, and (ii) compares the LQ and LQG active suspension designs from the point of view of stability robustness. The robustness of the LQ active suspensions is not necessarily good, and depends strongly on the design of a backup passive suspension in parallel with the active one. The robustness properties of the LQG active suspension controller are also investigated for several distinct measurement sets.

Copyright © 1994 by The American Society of Mechanical Engineers
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