Device and method of controlling steering system mounted in vehicles

A device controlling an assist torque to be outputted by a motor connected to a steering system mechanism generating a steering torque, comprising:

• a target generation unit generating a target steering torque, which is a target value of the steering torque;
• a response compensation filter where a filter process compensating for a response at a specific frequency band with respect to the inputted target steering torque is performed, and a response-compensated target steering torque is outputted;
• and
• a servo controller calculating a command value of the assist torque in order for a torque deviation, which is a difference between the steering torque and the target steering torque after compensating for the response, to become zero,
• wherein the response compensation filter has a transfer characteristic which is set to suppress a mechanical resonance characteristic at a frequency band having the mechanical resonance characteristic where a gain due to resonance of the steering system mechanism becomes great, with respect to a transfer characteristic from the target steering torque to the steering torque.