Valve feedback control with two opening degree sensors

摘要

In a throttle control system having two throttle opening sensors (4A and 4B), when one opening degree sensor being used in a PID feedback control becomes abnormal, the use of sensor output for throttle feedback control is switched from the abnormal one to normal one. Which of the throttle opening degree sensors (4A and 4B) has become abnormal is determined by monitoring the difference between the output values of the throttle opening degree sensors (4A and 4B) and the intensity of the electric current flowing to a DC motor (12) which drives a throttle valve (3). Further, when the abnormality in the another sensor (4B) being newly used is determined, the feedback control is continued based on the estimation of the throttle opening degree calculated by the output of the sensor (4B) before the malfunction thereof.