1995 Volume 7 Issue 2 Pages 432-441
This paper presents active and semi-active controls of suspension for compact passenger cars from the view-points of improvements of ride quality and vibration y using fuzzy reasoning. The cars are modelled by systems with four degrees of freedom, in which the restoring forces by suspension spings and the damping forces by shock absorbers are assumed to have nonlinear relations of suspension strokes and their derivatives, respectively. The strokes at the front/rear suspension locations are measured at the sampling instants. In the fuzzy reasoning, the measurements and their derivatives are treated as input variables in if-then fuzzy control rules. While, in the design fo active controls, the output variables are denoted as the control forces toe be inserted in the suspension locations, and in the design of semi-active controls, those are denoted as the damping forces of shock absorbers. The active and semi-active controls are determined so as to minimize the accelerations and displacements of vehicle body. That is, in the tuning of control policies, fuzzy control rules are assumed at the first step and secondly scale factors of membership functions characterizing fuzzy sets are modified, where two kinds of product-max gravity methods and two kinds of product-sum ones are considered as the defuzzyfier ones. The simulation results show that the proposed active and semi-active controls are more improved in suspension performance than passive control.
