Variable Structure Model Following Control For Automobile Active Suspensions

With the increase of automobile speed, people require a higher performance of ride and comfort. The passive suspension system used in automobile universally, whose parameters is fixed once it is designed, can't change with the status of automobile running and dynamic excitation, so the automobiles' capabilities are limited. However, active suspension absorbs the engine from outside equipment and adjusts the energy flow continually. The active suspension can adjust outside disturbance and meat higher capabilities. The key technique of active suspension is its control algorithm; whose validity and the method of processing signal affect the automobiles' performance. Considering the complexity of the road disturbance and the uncertainty of the controlled system, this paper studies the design of active suspension controller based on variable structure of model following controlFirstly, this paper discussed how to apply the sliding mode control theory to model following control system, namely, the principles of variable structure of model following control theory. According to automobile system dynamics theory, three different kinds of simple suspension mathematical models were established, namely, linear two degree of freedom models, linear four degree of freedom model and nonlinear two degree of freedom model. Otherwise, road excitation model was established accorded with related national standards.Then, a independent type active suspension based on the optimum control algorithm is established, which is adopted as the reference model. Combined with variable structure of model following control theory, the active suspension controller has been designed in the case of three models separately.Finally, the simulation models are established of active suspension and passive suspension for three different kinds of models. The simulation results indicated that, compared with the passive suspension, all the evaluation Indexes of suspension systems have improved. In addition, the controller also has a good robust performance for the change of controlled system's parameters.The studies of this paper indicted that, it is reasonable to design the active suspension controller based on VSMFC. This paper offers a valuable reference for the theory of active suspension controller.