Electric power steering apparatus

#This application is a National Stage of International Application No. PCT/JP2014/060093 filed Apr. 7, 2014, claiming priority based on Japanese Patent Application Nos. 2013-090650, filed Apr. 23, 2013, and 2014-075257, filed Apr. 1, 2014, the contents of all of which are incorporated herein by reference in their entirety.

#The present invention relates to an electric power steering apparatus that assist-controls a steering system of a vehicle by applying an assist force of a motor driving, through a reduction mechanism, with a current command value calculated based on at least a steering torque, and in particular to an electric power steering apparatus that suppresses a handle vibration (noisy sound) being caused by a handle inertia and a spring nature of a torsion bar and improves a steering feeling.

#An electric power steering apparatus that energizes a steering apparatus of a vehicle by using a rotational torque of a motor as an assist torque, applies a driving force of the motor as the assist torque to a steering shaft or a rack shaft by means of a transmission mechanism such as gears or a belt through a reduction mechanism. In order to accurately generate the steering assist torque, such a conventional electric power steering apparatus (EPS) performs a feedback control of a motor current. The feedback control adjusts a voltage supplied to the motor so that a difference between a steering assist command value (a current command value) and a detected motor current value becomes small, and the adjustment of the voltage applied to the motor is generally performed by an adjustment of duty command values of a pulse width modulation (PWM) control.

#In the accompanying drawings:

#FIG. 1 is a diagram illustrating a configuration example of a general electric power steering apparatus;

#FIG. 2 is a block diagram showing an example of a control system of the electric power steering apparatus;

#The present invention suppresses a handle vibration (noisy sound) being caused by a handle inertia and a spring nature of a torsion bar and improves a vibration that a driver feels uncomfortable and a steering feeling.

#Accordingly, an electric power steering apparatus according to the present invention performs a band pass filer (BPF)-process for a table output value (a vibration-damping compensation value 1) determined by a velocity-sensitive table corresponding to a motor velocity, or performs the BPF-process through the velocity-sensitive table corresponding to a factor (the steering angle velocity*the gear ratio) of a steering angle velocity (a differential component of the steering angle θ) by obtaining the steering angle velocity by differentiating the steering angle θ detected by the steering angle sensor and a gear ratio of a reduction mechanism obtained in advance. The present invention calculates a vibration-damping compensation command value by multiplying the output value (a vibration-damping compensation value 2) of the BPF with a gain due to the steering torque and again due to the vehicle speed. Further, the present invention corrects the calculated vibration-damping compensation command value by subtracting from the current command value of the steering assist, and suppresses the handle vibration by driving the motor with a corrected current command value. The factor of “the steering angle velocity*the gear ratio” is equivalent to the motor velocity ω.

#According to the electric power steering apparatus of the present invention, since the vibration-damping compensation command value is calculated by means of the velocity-sensitive table and the BPF by inputting the motor velocity or the factor of the steering angle velocity and the gear ratio, the vibration-damping compensation command value generates only at a steering active-return time, and it is possible to suppress the influences into another controls and the steering feeling to the minimum.