Control apparatus for steering system

A control apparatus for a steering system, the steering system being configured to turn turning wheels of a vehicle and including an electric motor, the control apparatus being configured to control the steering system, and the control apparatus comprising:

• control circuitry configured to perform
• an angle control process for controlling, to an angle command value, a convertible angle that is convertible into a rotational angle of the electric motor,
• a predetermined component calculation process for calculating a predetermined component containing at least one of two components that are a viscosity component and a friction component of the steering system, while using a value of a variable regarding a control quantity of the electric motor as an input, and
• a relationship change process for changing a relationship of an output from a control unit for the steering system to an input to the control unit, based on the predetermined component calculated through the predetermined component calculation process.