ADAPTIVE PID CONTROLLER WITH ON-LINE IDENTIFICATION

Jiří Macháček - Vladimír Bobál

   A digital adaptive PID controller algorithm which contains recursive identification is presented in this paper. It is performed for three types of discrete model: second order, third order and first order with time delay. The controller parameter design is derived from the ultimate (critical) gain and ultimate period of the system. The main part of the paper consists of simple algebraic expressions used to calculate the ultimate values. The basic condition for this is that the poles of the closed loop with ultimate gain lie on the stability boundary. This procedure can be implemented in all controller design methods based on the knowledge of the ultimate values, such as the well-known Ziegler-Nichols (Z-N) method.

Keywords: adaptive control, PID controllers, Ziegler-Nichols method, recursive least squares method, time delay system

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