Nonlinear Phenomena and Stability Analysis for Discretized Control Systems

Y. Okuyama (Japan)


Nonlinear control systems, discrete-time systems, discretization, quantization, robust stability, Popov criterion.


This paper analyzes the nonlinear phenomena and stability of discrete-time and discrete-value (discretized/quantized) control systems in a frequency domain. In this study, it is assumed that the discretization is executed on the input and output sides of a nonlinear element at equal spaces, and the sampling period is chosen of such a size suitable for the discretization in the space. Based on the premise, the discretized (stepwise) nonlinear characteristic is exam ined from two viewpoints, i.e., global and local. By par titioning the discretized nonlinear characteristic into two sections and by defining a sectorial area over a specified threshold, the concept of the robust stability condition for nonlinear discrete-time systems is applied to the discretized nonlinear control system in question. As a result, the non linear phenomena of a discretized control system are clari fied, and the stability of discretized nonlinear feedback sys tems is elucidated.

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