Fault diagnosis of parameter change type faults and a fault tolerant system design for servo systems

In this paper, we propose a new approach to the fault diagnosis and tolerant problem for the existing servo systems. Here we deal with such faults as represented by parameter changes of the coefficient matrices of a plant model, and we design a residual generator that indicates the fault occurrences by using the plant model. First, we propose such a design method of the residual generator by which we can obtain the fault information that the coprime factorization based approach loses, and show its design condition as well. Second, we also describe how to calculate the threshold between "fault" and "fault free" based on the bound of the measurement noise. On the other hand, in the design of the fault tolerant system, we first evaluate the influence of the fault on the servo system from the viewpoint of the closed loop stability and the response property of the noise. Second, based on the evaluation we construct a fault tolerant control (FTC) system by using the residual generator. Last, we show the efficiency of the proposed method by using numerical examples, and give the conclusion