Patent ID: 6810986
Filing Date: 2004-11-02
Classification: B62D

Abstract:
An electric power steering apparatus comprising:a steering torque detector section detecting steering torque applied through operation of a steering wheel and generating a steering torque signal indicative of the detected steering torque; a brushless motor capable of being PWM-driven with motor currents of at least three phases to give a steering torque assist to a steering system; a target current setting section setting target currents on the basis of at least the steering torque signal generated by said steering torque detector section; a motor current detection section detecting the motor currents to be supplied to said brushless motor and generating motor current signals indicative of the detected motor currents; an electrical angle detection section detecting an electrical angle of said brushless motor and generating an electrical angle signal indicative of the detected electrical angle; and a motor control unit comprising: an offset calculation section calculating offsets between the target currents and the motor currents on the basis of the motor current signals and generating offset signals indicative of the calculated offsets; a first control section reading the motor current signals generated by said motor current detector section, performing three-phase-to-two-phase conversion on the motor current signals and performing PI control on the offset signals; and a second control section reading the electrical angle signal generated by said electrical angle detection section, performing two-phase-to-three-phase conversion, using the electrical angle signal, to generate motor control signals and, on the basis of the motor control signals, generating the motor currents for driving said brushless motor, wherein an execution cycle time of control by said first control section is set to be longer than an execution cycle time of control by said second control section.