Conference Contribution

Transfer Function Parameter Identification by Modified Relay Feedback

Kristian Soltesz, Tore Hägglund, Karl Johan Åström


This paper proposes a transfer function parameter identification method, applicable to SISO systems of any order. Parameter identification is posed as a (non-convex) squared output error minimization problem, numerically solved utilizing Newton-Raphson iteration with back tracking line search. Focus lies on computing the cost function gradient and Hessian with respect to the parameter vector and on finding a feasible start point. The method is demonstrated for FOTD model identification. A modified relay non-linearity is utilized in order to obtain most input signal energy at a predefined phase, without a priori system information. The identification method is evaluated on a batch of common process industry processes. Finally, conclusions and suggestions on future work are provided.


relay, identification, parametric, transfer function, state space, FOTD


In Proc. American Control Conference 2010, In 2010 American Control Conference, Baltimore, Maryland, USA, June 2010.

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