Control device, electric power steering device, and control method

A control device that controls a steering assembly mounted on a vehicle, the control device comprising:

• a first assist controller to execute lane keeping control to keep the vehicle in a lane and generate a first input value;
• a second assist controller to generate a second input value based on a steering input value input from a steering wheel of the vehicle;
• and
• a disturbance sensitivity controller to which a command value calculated based on the first input value multiplied by a first gain and the second input value multiplied by a second gain is input;
• wherein
• the first gain and the second gain are variable values;
• when the first gain is set to K1 and the second gain is set to K2, K1=1−K2 is satisfied;
• the disturbance sensitivity controller includes a first model following controller to generate a correction value to correct the command value based on output of a control target including a motor provided in the steering assembly and a first nominal model based on a configuration of the control target;
• the first model following controller is configured or programmed such that a transfer function of the control target is restricted to a transfer function of the first nominal model in a frequency band in which a complementary sensitivity gain, which is a gain in a gain characteristic of a complementary sensitivity function with respect to a modeling error between the control target and the first nominal model, is one or substantially one;
• and
• the complementary sensitivity function includes a variable parameter that changes based on the second gain.