Study On Road Feeling Control Strategy For Vehicle Steer-By-Wire System

As the development of vehicle electronic technology and control theory, more and more chassis integrated control technology are applied to vehicles. Therefore, steer-by-wire system is used to vehicles as a novel electronic system, its large distinct comparing to traditional steering is the cancel between steering wheel and front wheels instead of wire, so we can improve vehicle maneuverability stability,active safety and driver's comfort by road feeling control and active control.This paper are aimed to study one key technology of steer-by-wire system-road feeling technology and combine with the project named "Research on Key Technology for Vehicle Steering-By-Wire system" and "Research on one Steering-By-Wire system". In this paper, we have a careful study and simulation test on road feeling control strategy for providing driver's comfortable and realistic road feeling. The main research work is summarized as follows:1) Establish a complete simulation system of SBWBased on veDYNA vehicle dynamic software and MatLab simulation software, we establish a complete model of steer-by-wire (consist of steering wheel, motor, rack and pinion, front wheel, etc) and finish the structure of steer-by-wire.The model is applicable to a variety of working conditions and is also used to test various algorithms. In this paper, we will use this model to simulate road feeling algorithms.2) Research on a direct measured current based method and velocity steering angle for road feeling control strategyBefore the study of road feeling control strategy, we firstly have a control of the actuator's torque which is the basis of realizing road feeling and the actuator must be have a slowly torque and good position tracking in order to transport a suitable current.For the master control of direct measured current based method, we can obtain road information (include aligning moment and property of tyre) indirectly from the actuator's torque produced by the actuator when it actuates steering task and provide driver's feeling information.Assistance control is aimed to the realistic road feeling property of steer-by-wire and is advanced based on master control. It can decrease the road feeling's torque between large angle, prevent heavy steering and improve steering system's road feeling.By the introduction of damping control for steer-by-wire, a driver can keep his line tracking when he is driving in dead area, thereby, it not only provide a driver's certain road feeling, but also prevent the oscillation of steering wheel and improve the road feeling in central area.In order to make a driver have the same road feeling as is the traditional steering in the limit of HW angle, we introduce the lock-to-lock control, which is simulated by increasing the torque in the limit of HW angle. For this, a driver can quickly suit to his driving habit when he drive the steer-by-wire vehicle.Moreover, we have a control on the target current of road feeling motor in order to make the motor transport suitable torque to driver, so we use PID algorithm after the dissertation between target current and real current for transporting voltage to make the motor produce suitable torque.3) Simulation test on the road feeling control strategyIn this paper, we choose some representative simulation test and working conditions to prove the road feeling control strategy. Firstly, we have a simulation comparison between different road feeling control to prove the rationality of various control strategy; Based on the free design of road feeling, we have some different result to meet various driver; Considering different maneuver conditions have its road feeling, so we have some simulation comparison between various velocity and frequency of HW. Finally, we choose "on-center steering" and "∞" test to test the design target of road feeling, from the result, we conclude the control strategy proposed above can make driver have a light steering in low speed and clear road feeling in high speed and then the algorithm is right, it also lay the theory foundation for the development of control unit in future real vehicle.