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Proportional-integral-derivative (PID) controllers with constant gains seldom meet desired performance when system dynamics rapidly changes due to unknown disturbances. A gain tuning method for variable PID controllers is presented in this paper. First, the equivalence relationship between a discrete PID control and a discrete backstepping control with time-delay estimation and nonlinear damping is clarified, and the variable gains of the PID controller are automatically tuned with a nonlinear damping component. The nonlinear damping terms directly affect system performance and make PID gains vary. The system performance of a variable PID controller with the proposed method is compared with that of a constant PID controller. The experimental results show that the proposed method is adaptive, robust, and effective.
Lee et al. (Thu,) studied this question.