| 摘要 |
In a power assisted steering system for a vehicle, an operator controlled steering shaft is connected directly to at least one steered wheel of the vehicle. An electric motor is connected to the steering shaft via a ratio reduction means. A clutch is interposed between the motor and the ratio reduction means to connect and disconnect the motor from the steering shaft. A control circuit senses torque and direction of rotation of the steering shaft by the operator and operates the motor to provide power steering assistance. The control circuit also monitors the operation of the system and, when the system is operating properly, keeps the clutch in engagement to transmit torque from the motor to the steering shaft. When the system is diagnosed to be operating improperly, the clutch is rapidly disengaged and the motor is effectively isolated from the steering shaft.
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