| 摘要 |
<p>A method is described for controlling the operation of a metering valve (10) driven by a stepper motor (24), a position sensor (30) normally providing position information to allow control over the metering valve (10) in a closed loop manner. The method comprises the steps of:
performing a calibration operation to derive a relationship between stepper motor position and metering valve position;
controlling the operation of the metering valve (10) in a closed loop manner; and
controlling the operation of the metering valve (10) in an open loop manner in the event that the position sensor output is thought to be unreliable; wherein, when operating in the open loop manner, the metering valve (10) is moved to a desired angular position by using the relationship derived in the calibration operation to determine the stepper motor position associated with the desired metering valve position and moving the stepper motor (24) to the determined stepper motor position.
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