Steering control apparatus and steering control method

A steering control method for a steering system to which a motor torque that reciprocates a wheel turning shaft of a steering mechanism is applied by an actuator that uses a motor as a drive source, the steering control method comprising:

• computing, by a controller, a torque command value that is a target value of the motor torque that the motor outputs;
• when an absolute value of a rotation angle of a rotary shaft exceeds a steering angle threshold for the steering system, computing, by the controller, a steering angle limit value that reduces with an increase in the absolute value of the rotation angle, the rotation angle of the rotary shaft being convertible to a wheel steering angle of a steered wheel coupled to the wheel turning shaft;
• setting, by the controller, a limit value to less than or equal to the steering angle limit value, the limit value being an upper limit of an absolute value of the torque command value;
• controlling, by the controller, the motor such that the motor torque follows the torque command value whose absolute value is limited to less than or equal to the limit value;
• computing, by the controller, a basic command value based on a steering torque;
• when the absolute value of the rotation angle exceeds the steering angle threshold, computing, by the controller, a damping control amount such that the damping control amount increases with an increase in an excess of an angular velocity of the rotary shaft over a first upper limit angular velocity set according to the absolute value of the rotation angle;
• and
• computing, by the controller, the torque command value based on a value obtained by combining the basic command value and the damping control amount such that an absolute value of the basic command value is reduced.