Steering control device

A steering control device that controls a steer-by-wire steering system for a vehicle, the steering control device comprising:

• a steering operation control circuit that controls a steering operation actuator of the steer-by-wire steering system in accordance with a steering state of a steering wheel, the steering system including (i) a reaction force actuator that applies a steering reaction force against an operation of the steering wheel, and (ii) the steering operation actuator that steers steered wheels via a steering operation shaft under a condition where power is not transmitted between the steered wheels and the steering wheel;
• and
• a reaction force control circuit that calculates the steering reaction force and changes the steering reaction force in accordance with changes in a calculated grip factor by varying an output of the reaction force actuator, the reaction force control circuit including:
• a first estimated axial force calculation circuit that calculates a first estimated axial force based on road surface information, the road surface information being calculated based on an axial force applied to each steered wheel of a plurality of steered wheels and a parameter of a current in the steering operation actuator, which is provided by a steering operation motor of the steering operation actuator;
• a second estimated axial force calculation circuit that calculates a second estimated axial force applied to the steering operation shaft based on a vehicle state quantity;
• and
• a grip factor calculation circuit that calculates the grip factor based on the first estimated axial force and the second estimated axial force.