The Research To The Fuzzy Controller On Semi-active Automobile Suspensions

The dynamic performance of suspension systems directly influences ride comfort and handling stability of driving vehicles. The fixed parameters of conventional suspension systems cause the tradeoff between these two factors. Semi-active suspensions, acting as the most advanced suspensions, could adjust the rigidity or damp actively and timely to reduce the vibration according to the working condition, and solve the contradictory perfectly. So the control system of semi-active suspension has been seen in many collaborative research projects.Control strategies, which are the kernel of the technology for semi-active suspension control system, greatly influence the suspension performance. In this paper, a new analytic method, which is based on the modern control theory and the dynamic suspension characteristic and semi-active suspension control system having referenced model or out of referenced model and influence result of simulation by Fuzzy controller of basic region and control rule and Fuzzy subset and contract fuzzy, is applied to the semi-active suspension control system.In this paper, a vehicle vibration model of 1/4 body with 2 degree-of-freedom is created, which is based on the vehicle dynamics theory. Considering the influence of the input disturbance, a mathematical description of road surface irregularity is established, which is the model of integral white noise and inspire with sine wave. After the modeling of input, semi-active suspension PID controller, semi-active suspension Fuzzy controller and semi-active suspension Self-adapt Fuzzy PID controller are designed respectively and the computer simulations are built with Matlab6.5 individually. To verify the robust of the control system, a sine signal and a random signal are added to the input separately. Finally, a simulation control software is developed in Matlab. This software has a friendly interface, which facilitates switch of different control modes and control parameters, as well as implements the control simulation for different disturbance inputs.According to the simulation results derived from time domain and frequency domain, we find that model out of conference is true, semi-active suspension Self-adapt Fuzzy PID control strategy is reasonable, feasible and scientific. Compared with passive suspension control, semi-active suspension Self-adapt Fuzzy PID control could reduce the bodywork acceleration in a large degree. When being compared with semi-active suspension PID control and Fuzzy control, severe vibration of the system are depressed considerably in the vicinity of resonant frequencies. The statistical results, which are obtained from the different input tests, indicate that the Self-adapt Fuzzy PID control based on semi-active suspension systems have fairly good robustness.