Study On Controller-order Reduction Of Vehicle Active Suspension System And Integrated Control

In order to improve the performance of active suspension system, control of active suspension has attracted researchers' interest. The performance of the active suspension system can be significantly improved, but the designed controller is often of high-order derived by the modern control theory, such as optimal control and robust control. The high-order controller will bring bad influences in the control system, for example its reliability will be worse and engineering implementation will be harder.The active suspension system and the electric power steering system are two important subsystems of the vehicle. After applying control to the two systems, the performances of the integrated system by simply combination of them are often unsatisfactory. The integrated control is an important direction.This thesis has carried out the following work for the above two problems.1. The model of a 7 degree-of-freedom active suspension system is firstly built, which has a minimal state-space realization with 14-order. Then an H_∞ controller is designed based on the model. The order-reduction problem of the high-order controller is studied by utilizing optimal Hankel-norm reduction method(OHNR). The controller-order can be largely reduced, and the closed-loop control performances are not degraded much. By compared with the modal truncation method and balanced truncation method, OHNR can obtain the best reduction effect.2. By utilizing model approximation minimization based and closed-loop performance optimum based methods respectively, the lower-order controller design problem is studied. By choosing appropriate weighted transfer functions, the stability of reduced-order closed-loop system could be maintained. By utilizing frequency-weighted coprime factorization based controller method, the order of active suspension controller can not only be considerably reduced, but also the lower-order controller could obtain the very similar closed-loop control performance with the full-order one.3. The integrated control of the active suspension system and electric power steering system is studied. Robust controller of active suspension and steeringintegrated system is designed. The performances are compared between the lower-order integrated control system consisting of the lower-order active suspension Hx control system and electric power steering PID control system and full-order one. The lower-order integrated control system could obtain the very similar control performances with the full one.4. The active suspension and electric power steering integrated control system for road test is designed. The assembly language and C51 language is utilized to compile P87C591 single-chip computer programme to realize the integrated control algorithm. The active suspension and electric power steering integrated control system indeed improves the vehicle handling and ride comfort.