OPTIMAL DESIGN OF AN ELECTRIC POWER STEERING SYSTEM FOR SPORT CARS

An accurate vehicle and steering system model has been developed and experimentally validated to investigate and to optimize the interaction between the vehicle and the electric power steering system. The most important electric power steering system parameters have been identified and varied to show their influence on steering wheel torque, steering feel and on the vehicle transient behaviour. Some standard tests related to vehicle transient response have been included to evaluate the performances of the electric power steering. The weave test manoeuver has shown to be very useful for a subjective and objective evaluation of the steering feel. An optimal control strategy for improving vehicle handling and steering feel during high speed driving has been defined. A theoretical analysis has been completed for increasing the frequency response bandwidth of steering angle, yaw rate, vehicle lateral acceleration relative to the steering torque input. The compensation of the friction and inertia effects is the main focus of the project on the basis of the accurate information on the state of motion of the steering system provided by the installed angular position sensors, i.e. the steering system control can use the steering wheel angular velocity as the feedback variable for friction/damping compensation.