| 摘要 |
An electric power steering controller which, when an assist command signal is absent or a PWM signal is off according to the assist command signal, keeps a steering wheel position without affecting on the steering operation even if an external force is applied to tires thereby improving steering operability. A switch controller 25 controls to turn on and off switches Q1 to Q4, which form an H-bridge circuit, to change a direction of a current flowing through an assist motor M1, thereby controlling to rotate the assist motor M1 and its rotating direction. For example, to rotate the assist motor M1 rightward, the switch Q4 is turned on, the switch Q1 is turned on or off according to an on-off signal of the PWM signal, and when the switch Q1 is on, a current I1 flows through the assist motor M1 to rotate it rightward. When an assist command is absent including a condition that the PWM signal is off when the assist motor M1 is rotated rightward, the switching control is performed to turn on the switches Q2 and Q4 only to form a closed circuit including the assist motor M1. Thus, the assist motor M1 is prevented from being rotated by an unexpected external force.
|
