Steering control device

A steering control device that is used as a controller for a steering system including:

• (i) a rotary shaft that is convertible to a steered angle of a steered wheel that changes with a steering angle of the steering wheel or operation of the steering wheel, (ii) an actuator configured to generate a force to be applied to a steering mechanism of a vehicle, the actuator including a reaction force actuator configured to generate a reaction force against operation of the steering wheel and a steering actuator configured to generate a force for steering the steered wheel, and (iii) a power transmission mechanism engaging and disengaging power transmission between the steered wheel and the steering wheel, in a state in which power transmission between the steered wheel and the steering wheel is disengaged, the steering control device comprising:
• a rotation angle control circuit that feedback controls the actuator or the reaction force actuator such that the steering angle of the steering wheel or a rotation angle of the rotary shaft respectively matches a target steering angle that is a target value of the rotation angle;
• an estimated axial force computation circuit that computes an estimated axial force in which a road-surface reaction force transmitted from a road surface to the steered wheel is reflected;
• a determination circuit that determines a change in characteristic of the estimated axial force;
• a compensation circuit that, based on the change in characteristic of the estimated axial force, compensates the estimated axial force so as to remove influence of the change;
• and
• a target steering angle computation circuit that computes the target steering angle based on the estimated axial force compensated by the compensation circuit.