| A diagnosis method of nonlinear factors in control system using the higher-order statistical properties of the output signal is presented in this paper, according to the bicoherence spectrum of the signal, two indicators has been defined: two indicators has been defined: Non-Gaussian index (NGI) and Nonlinear index (NLI); they are used to detect and quantitative analysis the nonlinear characteristics of control system. In contrast with the power spectrum, the simulation for the general thermal control system of the second-order object and the cascade-three parameters control system are carried out to verify the feasibility of this method. According to the diagnosis result of the main steam temperature from unit of a power plant before and after maintenance, the method proposed in this paper is the same with the actual situation. The algorithm,which takes Visual C++ as the development platform and performance evaluation software as the base, has been programmed to realize the function and embedded the nonlinear diagnosis sub-module into the performance evaluation software. |
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