Electric power steering device

An electric power steering device comprising:

• an electric motor for applying a steering power to a steering system;
• motor drive means for rotatably driving the motor, said motor drive means comprising a bridge circuit of two pairs of switching devices, each pair being controllable by a PWM signal and an ON signal;
• control means for providing said PWM signal and said ON signal to said motor drive means for actuating operation of said motor drive means based on a steering input to the steering system and such that said switching devices in each of said two pairs of switching devices are driven by said ON signal and said PWM signal, respectively;
• feedback means for providing a feedback signal to said control means indicative of a current flowing through said motor;
• said feedback means including a current detecting element connected in series with said motor, said motor and said current detecting element being disposed in series between the switching devices in each of said two pairs, and said control means selectively provide said PWM signal to different ones of said switching devices for rotation of the motor in clockwise and counterclockwise directions and such that said motor is disposed in series between said switching device to which said PWM signal is provided and said current detecting element whether said motor is rotated in the clockwise or the counterclockwise direction;
• and
• said control means including a target current setting unit for setting a target current signal for said motor, means for determining a deviation between the target current signal and said feedback signal indicative of the current flowing through said motor, and a drive control unit for outputting said PWM signal to said motor drive means based on the deviation determined by said determining means.

An electric steering device comprising:

• an electric motor for applying a steering power to a steering system;
• motor drive means for rotatably driving the motor in clockwise and counterclockwise directions, and including a bridge circuit composed of switching devices selectively drivable by a PWM signal;
• control means for providing said PWM signal to said motor drive means for actuating said motor drive means based on a steering input to the steering system;
• feedback means for providing a feedback signal to said control means indicative of a current flowing through said motor;
• said feedback means includes a current detecting element connected in series with said motor;
• said control means including a target current setting unit for setting a target current signal for said motor, means for determining a deviation between said target current signal and said feedback signal and a drive control unit for outputting said PWM signal to said motor drive means based on the deviation determined by said determining means;
• and
• said control means selectively provides said PWM signal to different ones of said switching devices such that the PWM signal is always isolated from said current detecting element by said motor and such that a high-frequency pulse noise generate by PWM driving of the switching devices is absorbed by inductance in said motor before a current flowing through said motor is detected by said current detecting element.