Research On Integrated Control Of Electrical Power Steering And Semi-active Suspension

The suspension and the steering system are two important subsystems of the vehicle chassis.They affect the vehicle dynamics performance,such as handling stability, the ride comfort,safety.The suspension and steering system affect each other and have some coupling effect between them. So the combintion apron string of the suspension and the steering system is very necessary.In this thesis.Fristly,The half-car and whole-car suspension model with containing uncertain parameters are established by using LFT. In order to ensure a robust stability for uncertain parameters, using the norm H∞ as the performance of the parameter uncertainty.The norm H2 is as the suspension performance indicators to measure disturbances for making the suspension system performance index in a good level,then Mixed H2 / H∞ controller is designed. The results of smulation indicates that the designed controller control of the suspension system have a good effect.Secondly H∞ controller of electric power steering system is designed by establishing the mechanical model of steering system,the two-freedom-degree machanical steering model, the motor model and the tire model.The results of smulation indicates that the designed controller can effectively reduce the fatigue of the driver and enhance the stability of the vehicle running. In order to further understand the coupling relationship between the two systems, a comprehensive model of suspension system and steering system is integrated and the coupling between the two systems are fully considered in the modeling. The comprehensive model is emulated in destinct input of steering angle. The results show that the effection of steering system on the suspension system is mainly reflected in the dynamic deflection of suspension, the tire deformation and the roll angle,have no effection on the pitch angular acceleration and the vertical acceleration.Finally, according to the coupling between the two systems, an upper coordinated controller is established by basing on each subsystem controller. This thesis adopts fuzzy control theory to design the upper coordinated controller.The simulation results show that the coordinated controller better than the separate subsystem controller as well as the superposition of the two system controller in the aspect of the overall performance of the vehicle, but in the tire deformation have no obvious advantage.It Weakens the coupling relationship between the two subsystem, enhances the multiple performance of the vehicle,offers the research basis on the study of integrated control system about steering and suspension system in future.