Robust PID controller autotuning with a phase shaper Chen Y.

Chen Y.
Количество страниц: 7
Язык: Английский
Формат: PDF / RAR

Формат файла: RAR

In our previous work (Chen et al., 2003a), a robust PID autotuning method was proposed by using the idea of "flat phase", i.e., the phase derivative w.r.t. the frequency is zero at a given frequency called the "tangent frequency" so that the closed-loop system is robust to gain variations and the step responses exhibit an iso-damping property. However, the width of the achieved phase flatness region is hard to adjust. In this paper, we propose a phase shaping idea to make the width of the phase flatness region adjustable. With a suitable phase shaper, we are able to determine the width of the flat phase region so as to make the whole design procedure of a robust PID controller much easier and the system performance can be enhanced more significantly. The plant gain and phase at the desired frequency, which are identified by several relay feedback tests in an iterative way, are used to estimate the derivatives of the amplitude and phase of the plant with respect to the frequency at the same frequency point by the well known Bode's integral relationship. Then, these derivatives are used to design the proposed robust PID controller. The phase shaper, based on the idea of FOC (Fractional Order Calculus), is actually a fractional order integrator or differentiator. In this paper, no plant model is assumed during the controller design. Only several relay tests and calculations are needed. Simulation examples illustrate the effectiveness and the simplicity of the proposed method with an iso-damping property.