Study Of Control Strategy To Exalting The Handling Of Automobile And Steering Reactive Torque For SBW System

Steering-By-Wire System (SBW), which is also called electric front wheel steering, cancelled mechanical linkage between the steering wheel and front wheel, so it get out of the restricting of traditional steering system and we can design the steering characteristic freely, it is a great renovation of steering system. Steering maneuver is detected through steering angle sensor and torque sensor. This information is transferred to a SBW controller, which use this sensor information and other sensor information to control the front wheel angle and steering wheel torque. So there is no conflict between the desirable angular ratio and hand wheel torque.The thesis focused on the simulation of steering reactive torque and determination of front wheel angle. The following is the mainly content of the thesis:Chapter one introduced development of steering system and configuration, principle, characteristic of the steer by wire system, and point out the key technology of steer by wire system.Chapter two introduced building of two testing platform, one is used for steer by wire system, the other is used for testing of the electromotor. To develop a steer by wire system successfully, it's necessary to do lot's of experimentation on real vehicle, only do this, can the performance of the system been adjusted to best status, but it's unavoidable to consume plenty of money, manpower and material resources. So it's necessary to build a testing platform on which we can test our control strategy. On the steer by wire testing platform, the control strategy such as steering executing electromotor, steering reactive torque simulating electromotor, groundresistance simulating electromotor and so on. While on the electromotor testing platform, we can test the performance of the electromotor.In chapter three, I constitute a mathematic model of steering executing system based on Santana's hydraulic power steering system, and then a vehicle model contain steer by wire system through the software Carsim.Chapter four researched control method of the steering executing electromotor, under the control principle of PID, electromagnetic torque of the electromotor can be calculated. The simulating results indicate that vehicle's real front wheel angle can follow the desired front wheel angle well. In this thesis, the yawrate of neutral steering vehicle is regarded as the ideal yawrate, two control strategies are introduced to make the yawrate of the vehicle follow the ideal yawrate.Chapter five analyse the reactive torque on steer wheel in different driving status, to get good road feeling, steering reactive torque should response the lateral force of the front wheel. In steering system, proper damping has positive effect, so in the simulated steering reactive torque, damping is included. The damping coefficient is relate to the steer wheel's return velocity, so it's important to confirm the value of it. After tested the steering reactive torque simulating electromotor's working characteristic on the electromotor testing platform, to get desired torque, the current of the electromotor can be calculated, then use the PID control principle to control the desired current.When vehicle's state change, steer by wire can actively produce an additional front wheel angle. But under the realistic condition, vehicle's driving appearance is very complicated, the additional front wheel angle maybe effect negatively. For example, when brake in a cure road, the additional front wheel angle produced by steer by wire may enlarge the turn radius of vehicle. That is dangerous and the driver may feel nervous. In future, the control of steer by wire should be integratedwith that of other active safety. When and which control should be put into effect should be studied.