Steer-by-wire steering system

A steer-by-wire steering system where a steering input device that receives a steering input by being steered by a driver is mechanically coupleable to or isolated from a steering operation device that causes a steered wheel to be steered in accordance with the steering input to the steering input device by the driver, the steer-by-wire steering system comprising:

• a steering-side motor that supplies the steering input device with a steering reaction force that opposes the steering input to the steering input device by the driver;
• a steered-side motor that supplies the steering operation device with a steering force that causes the steered wheel to be steered;
• and
• a power supply control circuit that controls a power supply to the steering-side motor such that the steering-side motor generates the steering reaction force in accordance with the steering input to the steering input device by the driver and that controls a power supply to the steered-side motor such that the steered-side motor generates the steering force that causes a steered angle of the steered wheel to follow a steering angle that changes on a basis of the steering input to the steering input device by the driver, wherein
• in response to determining that a duty ratio of a duty signal that is generated to control the power supply to the steered-side motor has reached a setting value that is predetermined to indicate that the steered angle becomes unable to follow the steering angle, the power supply control circuit controls the power supply to the steering-side motor such that the steering-side motor increases the steering reaction force.