Abstract
In this study, a practical controllable shock absorber (CSA) has been developed to establish its nonlinear mathematical model, including the dynamics of control valve, so as to investigate the improvements of the performance for semi-active suspension systems under the hardware limitations of CSA. Design constraints for preventing cavitaion have been derived to reduce the phenomena of force delay and to develop a CSA prototype. An instrumental shock absorber and the CSA prototype have been established for constant valve openings and varying valve openings. Consequently, an equation of damping force has been demonstrated to be capable of fully determining the damping force characteristics of the shock absorber under the design constraints. Meanwhile, GA-fuzzy system has also been demonstrated its feasibility on controller design for semi-active suspension systems by various road profiles, different design criteria, and several control intervals through computer simulations. During the controller design for the GA-fuzzy system, the nonlinear characteristics in semi-active suspension systems such as model of practical CSA, constraints of working space, and the feature of tire loose contact with the ground are all taken into consideration. Simulation results show that the improvements in ride comfort is achievable about 10 % to 20 % for random roads by the semi-active suspension systems under hardware limitations of the CSA prototype. While for accident roads, significant improvements of the performance are obtained in both ride comfort and handling. More than 30 % reductions in, 25% in, and 80% in near are obtained.