Optimization of the Dynamic Behavior of a Semi-Active Suspension Systems Subjected to Road Frequency


In this paper, two-degree-of-freedom linear model of quarter-car is used to derive a number of analytical formulae describing the dynamic behavior of semi-actively suspended vehicles running on randomly profiled roads. A simple power spectral density is considered for modeling the road irregularity. The proposed semi-active control law consists of two tunable parameters that are given as a function of the running conditions of the vehicle (i.e., excitation frequency, road roughness coefficient, and vehicle speed). An optimization method is applied to obtain the best compromise among conflicting performance indices pertaining to the vehicle suspension system (i.e., discomfort and road holding). Two objective functions (i.e., mean squares of the sprung-mass acceleration and the dynamic load) are minimized subjects to three constraints (i.e., maximum damping force, rattle space, and tire deflection). The proposed optimization method is developed based on the frequency regions (0-4 Hz, 4-8 Hz, 8-12 Hz, and 12 Hz and over). Passive, semiactive suspension systems with and without frequency regions subject to the simple road profile are compared in frequency domain analyses. The obtained result indicates that a semi-active suspension system has a significant potential in improving the ride comfort and the road holding.

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