Patent ID: 7386355

Claim:
A close loop control system, comprising: a controlled system, having a controlled variable and a control variable; a first detecting unit, for detecting the controlled system to output a first feedback value corresponding to the control variable; a second detecting unit, for detecting the controlled system to output a second feedback value corresponding to the control variable; and a feedback control unit, for controlling the controlled variable according to an absolute differential value of the first feedback value and the second feedback value, the feedback control unit comprising: a determining unit for receiving the first feedback value and the second feedback value and outputting a determining signal according to the absolute differential value of the first feedback value and the second feedback value; a controller, in response to the determining signal, wherein when the determining signal indicates that the absolute differential value is smaller than a predetermined error value, the controller of the feedback control unit adjusts the controlled variable according to a selected one of the first feedback value and the second feedback value, and controls the controlled variable according to the comparison between the selected one of the first and the second feedback values and a predetermined target value; and a register for storing at least an output value obtained from the feedback control unit, wherein the at least the output value comprises a fixed number of output values obtained from the feedback control unit; wherein when the determining signal indicates an abnormal situation where the absolute differential value is not smaller than the predetermined error value, the controller of the feedback control unit fixes the controlled variable to a fixed value based on an average value of the at least the output value stored in the register so that the controlled system is prevented from being stopped and out of control and continues to operate in the abnormal situation while the first detecting unit and the second detecting unit are able to be repaired or renewed.