Process frequency response estimation from relay feedback
ABSTRACT In this paper, a method for process frequency response identification is proposed, which can identify multiple points on process frequency response from a single relay feedback test. The process input and output transients resulting from a relay feedback cannot be directly converted to the frequency domain to obtain a process frequency response using FFT. A decay exponential is then proposed to modify the process input and output, so that the process frequency response can be identified with the help of FFT. Real-time testing of the method on various processes gives quite accurate process frequency responses, especially in the frequency range [0, ωc], which is important for control design and process modelling. The method inherits and extends the advantages of the original relay auto-tuning technique. It can be easily applied to PID auto-tuning and to transfer function modelling.
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ABSTRACT: In this paper, a new identification method performed in the time domain based on the decentralized step-test is proposed for two inputs and two outputs (TITO) processes with significant interactions. In terms of parameter identification, the coupled closed-loop TITO system is decoupled to obtain four individual single open-loop systems with the same input signal. As in the SISO case, new linear regression equations are derived, from which the parameters of a first- or second-order plus dead-time model can be obtained directly. The proposed method outperforms the existing estimation methods for multivariable control systems that use step-test responses. Furthermore, the method is robust in the presence of high levels of measurement noise. Simulation examples are given to show both effectiveness and practicality of the identification method for a wide range of multivariable processes. The usefulness of the identified method in multivariable process modeling and controller design is demonstrated.Asian Journal of Control 05/2005; 7(2):154 - 162. · 1.41 Impact Factor
Conference Proceeding: Hammerstein Modeling of Electrical Drives: Identification by Multiple Integrators[show abstract] [hide abstract]
ABSTRACT: In this paper the authors propose a novel method in order to identify the Hammerstein model where the nonlinear process is approximated by a static nonlinear element followed by a linear dynamic second or third-order model. The method is able to determine the parameters of the linear plant and two point of the nonlinear element in a unique step by using a filtered equation and the least-squares method. One of the most significant simulation example applied to the identification of a dc-engine is reported; it demonstrates the effectiveness of the proposed method and its acceptable robustness to disturbance and to measurements noise.Power Engineering, Energy and Electrical Drives, 2007. POWERENG 2007. International Conference on; 05/2007
Conference Proceeding: Transfer function identification by using self-oscillations[show abstract] [hide abstract]
ABSTRACT: The work presented in this paper deals with the process of transfer function identification by using self-oscillation method (autotuning identification method). The algorithm is given in a general matrix form and some modifications are introduced. The modifications of the algorithm include augmentation of the initial algorithm for Type k systems, systems with delays and discrete-time systems. The paper also includes simulation examples which describe the introduced modifications. Apart from being rather simple, this method is applicable to real systems. Its greatest advantage is quick identification of a transfer function (depends on the system).Control & Automation, 2007. MED '07. Mediterranean Conference on; 07/2007