ON METHODS FOR GRADIENT ESTIMATION IN IFT FOR MIMO SYSTEMS

Abstract Iterative feedback tuning (IFT) is a model free control tuning method using closed loop experiments. For single-input single-output (SISO) systems only 2 or 3, depending on the controller structure, closed loop experiments are required. However for multivariable systems the number of experiments increases to a maximum of 1 + m × p, where m × p is the dimension of the controller. In this contribution several methods are proposed to reduce the experimental time by approximating the gradient of the cost function. The local convergence for a method which uses the same technique as in IFT for SISO systems is analyzed. It is shown that even if there are commutation errors due to the approximation method, the numerical optimization may still converge to the true optimum.

[1]  B. Codrons,et al.  Iterative identificationless control design : Feature issue controller tuning , 1997 .

[2]  Michel Gevers,et al.  Iterative weighted least-squares identification and weighted LQG control design , 1995, Autom..

[3]  Lennart Ljung,et al.  Adaptive control based on explicit criterion minimization , 1985, Autom..

[4]  H. Hjalmarsson.  Efficient tuning of linear multivariable controllers using iterative feedback tuning , 1999 .

[5]  Svante Gunnarsson,et al.  Iterative feedback tuning: theory and applications , 1998 .

[6]  S. Gunnarsson,et al.  A convergent iterative restricted complexity control design scheme , 1994, Proceedings of 1994 33rd IEEE Conference on Decision and Control.

[7]  F. De Bruyne,et al.  Iterative controller optimization for nonlinear systems , 1997, Proceedings of the 36th IEEE Conference on Decision and Control.

[8]  Michel Gevers,et al.  Model-free Tuning of a Robust Regulator for a Flexible Transmission System , 1995, Eur. J. Control.

[9]  J. Sjoberg,et al.  Nonlinear controller tuning based on linearized time-variant model , 1997, Proceedings of the 1997 American Control Conference (Cat. No.97CH36041).

[10]  Pierre Carrette,et al.  Synthetic generation of the gradient for an iterative controller optimization method , 1997, 1997 European Control Conference (ECC).

[11]  Michel Gevers,et al.  Iterative Feedback Tuning: theory and applications in chemical process control , 1997 .

[12]  Sandor M. Veres,et al.  Iterative design for vibration attenuation , 1999 .

[13]  Lennart Ljung,et al.  Analysis of recursive stochastic algorithms , 1977 .

[14]  M. Agarwal,et al.  Model-free repetitive control design for nonlinear systems , 1996, Proceedings of 35th IEEE Conference on Decision and Control.

[15]  Håkan Hjalmarsson,et al.  Control of nonlinear systems using iterative feedback tuning , 1998, Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207).

[16]  J. Sjöberg,et al.  On a Nonlinear Controller Tuning Strategy , 1999 .