Multivariable Process Identification and Control From Decentralized Relay Feedback

Abstract The relay auto-tuning technique for PID controllers is being extended to tune multivariable controllers. In this paper, an auto-tuning method for multivariable controllers from decentralized relay feedback is proposed. The frequency response of an m × m multivariable process is identified from a decentralized relay test using an FFT-based method. For multivariable controller tuning, a new set of design equations are derived under the decoupling conditions, where the equivalent diagonal plants are independent of off-diagonal elements of the controller and used to design its diagonal elements first. The PID parameters of the controllers are determined individually with linear least squares frequency response defined on the basis of the identified frequency responses. Various typical examples are included for illustration of the effectiveness of this method.

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