Control apparatus for power steering apparatus and power steering apparatus using the same

A power steering apparatus comprising:

• a steering mechanism configured to turn a turning target wheel according to a steering operation performed on a steering wheel;
• a brushless motor configured to provide a steering force to the steering mechanism;
• and
• a control apparatus configured to drive and control the brushless motor, the control apparatus including
• a current instruction value calculation portion configured to calculate a current instruction value directed to the brushless motor according to a driving condition of a vehicle;
• a voltage instruction value calculation portion configured to calculate a voltage instruction value directed to the brushless motor based on the current instruction value;
• a PWM control portion configured to output a PWM duty signal to each phase of the brushless motor according to the voltage instruction value;
• a bridge circuit including a switching circuit configured to be driven and controlled by the PWM duty signal, the bridge circuit being configured to drive and control the brushless motor;
• a control period setting portion configured to changeably set a control period, the control period being a period based on which the control apparatus performs a control operation;
• a PWM carrier period setting portion configured to set a natural number of PWM carrier periods within one period of the control period, the PWM carrier period being a period based on which the PWM duty signal is switched between on and off, the PWM carrier period setting portion being further configured to changeably set a length of the PWM carrier period;
• a motor current detection execution portion configured to detect a motor current, which is a current flowing in the brushless motor, during the control period;
• a motor rotational angle detection execution portion configured to detect a motor rotational angle, which is a rotational angle of a rotor of the brushless motor, during the control period;
• an execution timing setting portion configured to set a timing at which the motor current is detected by the motor current detection execution portion or a timing at which the motor rotational angle is detected by the motor rotational angle detection execution portion, based on the control period set by the control period setting portion;
• and
• a motor rotational angle estimation portion configured to estimate the motor rotational angle when the motor current is detected by the motor current detection execution portion, based on the control period set by the control period setting portion and the motor rotational angle detected by the motor rotational angle detection execution portion,
• wherein the current instruction value calculation portion is configured to calculate the current instruction value based on the motor current and the motor rotational angle when the motor current is detected.

A system to control a brushless motor for power steering, the system comprising:

• a control apparatus configured to
• calculate a current instruction value for the brushless motor according to a driving condition of a vehicle;
• calculate a voltage instruction value for the brushless motor based on the current instruction value;
• output a pulse width modulation (PWM) duty signal to each phase of the brushless motor according to the voltage instruction value;
• set a control period based on which the control apparatus performs a control operation;
• set a natural number of PWM carrier periods within one period of the control period, at least one PWM carrier period of the PWM carrier periods being a period based on which the PWM duty signal is switched between an on state and an off state, and set a length of the at least one PWM carrier period;
• detect a motor current and a motor rotational angle of the brushless motor during the control period;
• set a timing at which the motor current or the motor rotational angle is detected, based on the set control period;
• estimate the motor rotational angle when the motor current is detected, based on the set control period and the detected motor rotational angle;
• and
• calculate the current instruction value based on the motor current and the motor rotational angle when the motor current is detected, and
• a bridge circuit configured to control the brushless motor, the bridge circuit including a switching circuit configured to be driven and controlled by the PWM duty signal.