抄録
This paper proposes a practical identification method of nonlinear plants with the Hammerstein-type model by using the relay feedback limit cycle test. Almost all industry plants are nonlinear and the controllers for the plant should be designed considering the nonlinear characteristics of the plant to achieve high control performances. But, practically, it is not an easy work to identify the nonlinear characteristics of the plant. In general, there are many types of nonlinear characteristics, and a nonlinear model of the plant has high degrees of freedom. For this problem, some nonlinear models consist of static nonlinear blocks and linear dynamic blocks are proposed. The Hammerstein model is a nonlinear plant model consists of a nonlinear block at the input and a linear dynamic block. This paper shows the identification method of the input nonlinear block characteristics. The identification test is a limit cycle test with a relay feedback configuration. By changing the output values of the relay element, the nonlinear block property can be estimated with the duty ratios and the deviation amplitudes of the plant output. This identification test is practical and the dynamic block can also be identified with the test. Furthermore, the input nonlinear characteristics can be estimated almost independently of the output and feedback nonlinear characteristics because of the small deviation of the plant condition during the relay feedback. A numerical simulation example is shown to illustrate the procedure of the proposed identification method.
