Research On Transparency And Stability Of SBW System With Bilateral Control Structure

Steer-by-Wire(SBW) system, in which the mechanical linkage between the steering wheel and the steering gear is eliminated, implements the steering input of the driver and provides the road feeling to the driver by controlling steering motor and the road feeling motor respectively. SBW system is one kind of bilateral control system,for the controller of SBW system controls two modules at the same time and there exits the coupling of angle and torque between the steering wheel module and the steering execution module. The bilateral control method can be applied in SBW system.This paper is supported by the National Natural Science Fund Project named “Research on the control mechanism and evaluation method of a new steer-by-wire system based on the characteristics of the drivers”(No. 51575223) and the National Natural Science Young Fund Project named “Research on Joystick and Bilateral Control Strategy for Steer-by-Wire Vehicle”(No.51105165). The analysis method based on the impedance theory is used to analyze the transparency of the SBW system with different bilateral structures. The wave variables control method is applied in the SBW system to keep the system stable. The main research work is summarized as follows:1. Establishing simulation model of SBW systemThe simulation platform of SBW system is established with Carsim and Matlab/ Simulink. The model of steering system is established with Simulink. The vehicle model is from Carsim and the parameters of the model is similar to those of the SBW test vehicle. How to set the interface between the vehicle model and the steering system model is explained in detail.2. Transparency analysis of SBW system with bilateral control structureBased on the summary of the bilateral control structures applied in SBW system, the transparency analysis method based on the impedance theory is used to compare the transparency of the force feedback-position structure and torque drive/angle feedback structure. The simulation model is further implemented with the torque drive/angle feedback structure and simulation experiments is carried out. By comparing the simulation results with the vehicle model with EPS system, the SBW system with torque drive/angle feedback structure is proved to have good transparency.3. Stability control of SBW systemThe Lievellyn stability criteria is used to analyze the influencing factors of the stability of SBW system. The wave variables control method based on passive theory is used to keep SBW system stable. Simulation experiments are conducted to prove the validity of the method. At the same time, the design method of force transmission ratio is introduced. The force transmission ratio applied in the simulation experiments in this paper is based on the rack power curve from Carsim. The experiments results verify the rationality of the force transmission ratio.4. Vehicle experiments of SBW system with bilateral control structureThe test platform of SBW system is established with the real time technology d SPACE. Vehicle experiments are conducted to verify the validity of the bilateral control method. The results show that the SBW system with the torque drive/angle feedback bilateral control structure has good transparency and stability.