| 摘要 |
An electric power steering system (100) for vehicles comprising a drive control circuit (15) for executing a motor drive process (106-111) for feeding an output signal (Va) to an electric motor (11) for supplying auxiliary torque (Ts) to a steering shaft (1,2), in dependence on an output signals (S1-S4) from a sensor (9, 10) for detecting a steering state of the steering shaft, and further a trouble-diagnostic process (113-115) of the system, the drive control circuit including a micro-computer unit (22). The system further comprises a diagnostic proportion changing mechanism (14, 103-105, 112, 116) which is operatively connected to the drive control circuit and changes the proportion of execution of the trouble-diagnostic process to the motor drive process in dependence on the vehicle speed (V). The diagnostic proportion changing mechanism has the execution frequency of the trouble-diagnostic process set so as to be small at a relatively low vehicle speed, increased with increase in vehicle speed, and large at a relatively high vehicle speed.
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