Patent ID: 9592849
Date: 2017-03-14
CPC Classifications: B62D

Claim:
1. An electric power steering system for a vehicle equipped with a steering mechanism through which steering power is transmitted from a mechanical steering member which is manually operated by a vehicle operator of a system vehicle having this system mounted therein comprising: an electric motor which is joined to the steering mechanism and works to output torque for steering the system vehicle; a torsion bar which is installed in the steering mechanism and located between the mechanical steering member and a joint of the electric motor and the steering mechanism; a torsion sensor which measures twisting of the torsion bar as a steering torque; an assist controller which works to determine an assist command as a function of the steering torque, as derived by the torsion sensor, the assist command being to produce assist torque through the electric motor for assisting in turning the mechanical steering member; a target tracking controller which works to determine a tracking command which produces through the electric motor automatic steering torque which brings a value of a given physical quantity associated with steering of the system vehicle into agreement with a target value; a vibration correction controller which works to calculate a vibration correction torque which suppresses vibration of the steering torque which arises from output of the torque from the electric motor based on a transfer characteristic of transmission of the output of torque from the electric motor as a part of the steering torque, said vibration correction controller determining a vibration correction command to produce the vibration correction torque through the electric motor; and a motor driver which works to actuate the electric motor based on sum of the assist command, the tracking command, and the vibration correction command.