ELECTRIC POWER STEERING SYSTEM

摘要

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a means used in an electric power steering system to control the steering force in accordance with the behavior of the vehicle turning. SOLUTION: An additional reaction torque setting means 4 comprises a normative steering force calculating means 4a to calculate a normative steering force in accordance with a coefficient of road frictionμand a steering angleθs, and an additional reaction torque calculating means 4b to calculate an additional reaction in accordance with the deviation of an actual steering force from the normative steering force. An additional reaction torque command value TC that the setting means 4 sets is added to an auxiliary steering torque command value, which sum is used for the computation of control signals for controlling the output of the motor of a power steering system. The above constitution reduces the manufacturing cost of an electric power steering system having the quality function of executing its reaction application control to the dynamic steering force with no employment of expensive lateral-acceleration sensors to thus optimize the steering force in accordance with road surface conditions.