Electric power steering apparatus

An electric power steering apparatus that comprises a torsion bar which is provided in a column shaft of a steering wheel of a vehicle, and assist-controls a steering system by driving and controlling a motor connected to said column shaft based on a current command value, the electric power steering apparatus comprising:

• at least one hardware processor configured to implement:
• generating a target steering torque reference based on vehicle driving information;
• converting said target steering torque reference into a target torsional angle reference, using a spring constant of said torsion bar;
• calculating said current command value based on at least said target torsional angle reference and a torsional angle value of said torsion bar;
• inputting a steering state which indicates right-turning or left-turning of said steering wheel;
• outputting, via a basic map, a first torque signal being vehicle speed sensitive, depending on said vehicle driving information;
• performing hysteresis correction corresponding to said vehicle driving information depending on said steering state and output a second torque signal;
• outputting a third torque signal obtained by multiplying a differential value of said vehicle driving information by a vehicle speed sensitive damper gain;
• outputting said target steering torque reference by adding said second torque signal and said third torque signal to said first torque signal;
• outputting a target torsional angular velocity value corresponding to a deviation between said target torsional angle reference and said torsional angle value;
• inputting said target torsional angular velocity value and a torsional angular velocity value;
• calculating and outputting said current command value so that said torsional angular velocity value follows said target torsional angular velocity value;
• performing feedback to said current command value by setting a transfer function to at least one of angle relation information;
• and
• performing a control so that said torsional angle value follows a value depending on said vehicle driving information.