Simulation Study Of Control Stategies For Vehicle Active Suspension

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. Active suspensions, acting as the most advanced suspensions, could adjust the control force actively and timely to reduce the vibration according to the working condition, and solve the contradictory perfectly. So the control system of active suspension has been seen in many collaborative research projects.Control strategies, which are the kernel of the technology for active suspension control system, greatly influence the suspension performance. In this paper, a new control strategy, Self-adapt Fuzzy PID control mechanism, which is based on the modern control theory and the dynamic suspension characteristic, is applied to the active suspension control system. This strategy combines the advantages of PID control and Fuzzy control. It implements the self-adjusting of these three parameters Kp, Ki, and Kd in the control system by using Fuzzy controller and improves the suspension performance gradually.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. After the modeling of input, active suspension PID controller, active suspension Fuzzy controller and 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 language. 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 active suspension Self-adapt Fuzzy PID control strategy is reasonable, feasible and scientific. Compared with passive suspension control, active suspension Self-adapt Fuzzy PID control could reduce the bodyworkacceleration in a large degree. When being compared with active suspension PID control and Fuzzy control, severe vibration of the system are depressed considerably in the vicinity of resonant frequencies, 1Hz~10Hz. The statistical results, which are obtained from the different input tests, indicate that the Self-adapt Fuzzy PID control based on active suspension systems have fairly good robustness.Given the time-variability parameters and the nonlinearities in automotive suspension, the new strategy is employed to control the nonlinear characteristics of the suspension system. It has been shown by simulation analyses that the active suspension Self-Fuzzy PID control is applicable and effective remarkably. It also offers a new idea to the field of research on suspension control strategies.