Pid Self-Tuning Controllers Used in Different Structures of the Control Loops
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The paper investigates the behavior of digital PID self-tuning controllers (STC) in different structures of the control loops used in adaptive systems. In the two phases of this type of systems which use a STC-PID, the first phase, i.e. the task of recursive identification of the plant model parameters, is used a regression (ARX) model with the recursive least squares method. Because the quality of process model depends on the order of the ARX model and of the sample period (Ts), the digital PID parameters are functions of these variables and, supplementary, of continuous-time PID parameters and of the control loop structures used in the adaptive system (although, not so largely as the firstly three variables).