Research on control strategy and bench test of automobile Steer-by-Wire system

Abstract

Steering by Wire system is a revolution of steering system structure and function.lt cuts off the mechanical connection between steering wheel and steered wheels ,controls the steering motor to steer front wheels actively so as to improve handling and stabilities and active safety,and controls steering wheel motor to supply the driver with ideal road feel. First, driver-vehicle-road closed loop models of Steering by Wire system are built based on Matlab/Simulink.Model parameters are optimized using genetic algorithm. Upper control strategies of Steering by Wire system include active steering control strategy ,which include feed forward type and feedback type,and road feel control strategy. Steering ratios under different velocities are optimized by genetic algorithm with closed -loop total variance as fitness function in feed forward type of steering control strategy.Yaw rate is feedback to increase system damp and bandwidth and improve stability in feedback type of steering control strategy. One road feel control strategy adjusts steering wheel feedback torque according to steering wheel angle and velocity .In the other road feel control strategy,tire restoring torque is estimated to supply the driver with appropriate road feel.Evaluation of road feel is analyzed. In lower control strategy,PID control is adopted to control steering motor to realize target front wheel angles determined by active steering control strategy and controls front wheel motor to realize target steering wheel feedback torques determined by road feel control strategy. Finally, Steering by Wire system bench test is conducted to evaluate both steering and road feel control strategies.