A fuzzy-logic approach to semi-active vehicle suspension design is developed, with the goal of improving the speed of the vehicle over very rough, off-road, terrain. The ride metric used for quantifying improvements is the absorbed power of the sprung mass of the vehicle. Particular attention is made to the proper modeling of the suspension using both the full kinematic constraints and the more convenient two degree of freedom model of the quarter vehicle suspension. Nonlinearities of the suspension, including tire stiffness and bumpstops are included at all stages to demonstrate the controller performance advantages. The semi-active control law is developed on the less complex model, and the results of tuning in the fully constrained environment are compared.
The results of this work have broad appeal, from the ease of development of the fuzzy-logic based algorithms, to the cost effectiveness of the semi-active hardware implementation. Improvements in the performance of the suspension system are desirable to the increasingly popular sport utility and light truck markets, as well as to military and emergency vehicle designs.