In this paper, the applicability of iterative feedback tuning (IFT) to internal model controllers... more In this paper, the applicability of iterative feedback tuning (IFT) to internal model controllers (IMCs) and smith predictors is examined. IFT is a model-free gradient descent controller tuning tool; refer to Hjalmarsson et al. (IEEE Control Systems Mag. 18 (1998) 26) and Hjalmarsson et al. (Proceedings of the Conference on Decision and Control, Orlando, FL, 1994, pp. 1735) for further details. It is shown that the IFT algorithm can be modified to tune IMCs and, more in particular, Smith predictors. The main difference with the original algorithm is that the cost gradient is obtained by doing four experiments (two recycling experiments) instead of three (one recycling experiment) for conventional controllers.
Recently, a data-driven model-free iterative control designmethod has been proposed in [4]. This ... more Recently, a data-driven model-free iterative control designmethod has been proposed in [4]. This contributionreports an experimental study with this method when appliedto a ball-on-beam system. This setup has nonlineardynamics and suffers from nonlinear friction. The methodis modified so as to allow its applicability when the secondexperiment that is described in [4] becomes a nuisance.The new concepts of synthetically generated gradients andline searches along the descent direction are ...
In [8] a new model validation method was proposed that is based on the estimation of an unbiased ... more In [8] a new model validation method was proposed that is based on the estimation of an unbiased model of the model error which relates the inputs to the simulation errors. In this paper, we extend this methodology to closed-loop validation, i.e. the validation of an open-loop model on the basis of closed-loop validation data. We show that, perhaps surprisingly, the same model may fail to be validated with open-loop data, while it is validated by data collected in closed loop. In addition, we show that the uncertainty sets generated by models validated in closed loop are better tuned towards control design, i.e. the controllers that stabilize all members of such a set are less conservative than those that stabilize all members of a set validated in open loop. The comparison between both methods is illustrated by means of a numerical example.
In this paper, we present a modification of a closed-loop identification scheme known as the “Han... more In this paper, we present a modification of a closed-loop identification scheme known as the “Hansen scheme”. The advantage of the alternative procedure is that the order of the resulting model is tunable by the user.
In 8] a new model validation method was proposed that is based on the estimation of an unbiased m... more In 8] a new model validation method was proposed that is based on the estimation of an unbiased model of the model error which relates the inputs to the simulation errors. In this paper, we extend this methodology to closed-loop validation , i.e. the validation of an open-loop model on the basis of closed-loop validation data. We show that, perhaps surprisingly, the same model may fail to be validated with open-loop data, while it is validated by data collected in closed loop. In addition, we show that the uncertainty sets generated by models validated in closed loop are better tuned towards control design, i.e. the controllers that stabilize all members of such a set are less conservative than those that stabilize all members of a set validated in open loop. The comparison between both methods is illustrated by means of a numerical example.
In this contribution, we extend the Iterative Feedback Tuning (IFT) control method of[3, 4] to a ... more In this contribution, we extend the Iterative Feedback Tuning (IFT) control method of[3, 4] to a multivariable setting. We report on an experimental study with this methodwhen applied to a Single-Input-Multiple-Output torsional laboratory setup.Keywords: Optimal control, estimation, laboratory application1 IntroductionA torsional control system available in the Department of Sytems Engineering at theAustralian National University has been considered as a test
Proceedings of the 1999 American Control Conference (Cat. No. 99CH36251), 1999
Presents an identification-based mechanism for introducing guaranteed stability when using a data... more Presents an identification-based mechanism for introducing guaranteed stability when using a data-driven model-free iterative control design method known as iterative feedback tuning. Also, the use of unbiased estimates of the Hessian is shown to significantly improve the user control over the tuning procedure
Proceedings of the 38th IEEE Conference on Decision and Control (Cat. No.99CH36304)
Presents a nonlinear extension of the ν-gap metric introduced in Vinnicombe (1993). Indeed, we pr... more Presents a nonlinear extension of the ν-gap metric introduced in Vinnicombe (1993). Indeed, we present an input-output version of the generalized stability margin and the ν-gap metric. The notion of image representation as presented in van der Schaft (1996) allows one to use these alternative definitions in a nonlinear context for the derivation of a robust stability theorem
Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998
We present a closed-loop parametric identification setup that allows the estimation of both the i... more We present a closed-loop parametric identification setup that allows the estimation of both the input-output and noise dynamics. The method is based on the minimization of a standard identification criterion and a parametrization that is tailored to the closed-loop configuration
In this paper, the family of algorithms presented previously by the authors (1999) is extended fo... more In this paper, the family of algorithms presented previously by the authors (1999) is extended for the identification of continuous time nonlinear plants operating in closed-loop. The main novelty is that the identification of unstable plants is covered in its generality
In this paper, the applicability of iterative feedback tuning (IFT) to internal model controllers... more In this paper, the applicability of iterative feedback tuning (IFT) to internal model controllers (IMCs) and smith predictors is examined. IFT is a model-free gradient descent controller tuning tool; refer to Hjalmarsson et al. (IEEE Control Systems Mag. 18 (1998) 26) and Hjalmarsson et al. (Proceedings of the Conference on Decision and Control, Orlando, FL, 1994, pp. 1735) for further details. It is shown that the IFT algorithm can be modified to tune IMCs and, more in particular, Smith predictors. The main difference with the original algorithm is that the cost gradient is obtained by doing four experiments (two recycling experiments) instead of three (one recycling experiment) for conventional controllers.
Recently, a data-driven model-free iterative control designmethod has been proposed in [4]. This ... more Recently, a data-driven model-free iterative control designmethod has been proposed in [4]. This contributionreports an experimental study with this method when appliedto a ball-on-beam system. This setup has nonlineardynamics and suffers from nonlinear friction. The methodis modified so as to allow its applicability when the secondexperiment that is described in [4] becomes a nuisance.The new concepts of synthetically generated gradients andline searches along the descent direction are ...
In [8] a new model validation method was proposed that is based on the estimation of an unbiased ... more In [8] a new model validation method was proposed that is based on the estimation of an unbiased model of the model error which relates the inputs to the simulation errors. In this paper, we extend this methodology to closed-loop validation, i.e. the validation of an open-loop model on the basis of closed-loop validation data. We show that, perhaps surprisingly, the same model may fail to be validated with open-loop data, while it is validated by data collected in closed loop. In addition, we show that the uncertainty sets generated by models validated in closed loop are better tuned towards control design, i.e. the controllers that stabilize all members of such a set are less conservative than those that stabilize all members of a set validated in open loop. The comparison between both methods is illustrated by means of a numerical example.
In this paper, we present a modification of a closed-loop identification scheme known as the “Han... more In this paper, we present a modification of a closed-loop identification scheme known as the “Hansen scheme”. The advantage of the alternative procedure is that the order of the resulting model is tunable by the user.
In 8] a new model validation method was proposed that is based on the estimation of an unbiased m... more In 8] a new model validation method was proposed that is based on the estimation of an unbiased model of the model error which relates the inputs to the simulation errors. In this paper, we extend this methodology to closed-loop validation , i.e. the validation of an open-loop model on the basis of closed-loop validation data. We show that, perhaps surprisingly, the same model may fail to be validated with open-loop data, while it is validated by data collected in closed loop. In addition, we show that the uncertainty sets generated by models validated in closed loop are better tuned towards control design, i.e. the controllers that stabilize all members of such a set are less conservative than those that stabilize all members of a set validated in open loop. The comparison between both methods is illustrated by means of a numerical example.
In this contribution, we extend the Iterative Feedback Tuning (IFT) control method of[3, 4] to a ... more In this contribution, we extend the Iterative Feedback Tuning (IFT) control method of[3, 4] to a multivariable setting. We report on an experimental study with this methodwhen applied to a Single-Input-Multiple-Output torsional laboratory setup.Keywords: Optimal control, estimation, laboratory application1 IntroductionA torsional control system available in the Department of Sytems Engineering at theAustralian National University has been considered as a test
Proceedings of the 1999 American Control Conference (Cat. No. 99CH36251), 1999
Presents an identification-based mechanism for introducing guaranteed stability when using a data... more Presents an identification-based mechanism for introducing guaranteed stability when using a data-driven model-free iterative control design method known as iterative feedback tuning. Also, the use of unbiased estimates of the Hessian is shown to significantly improve the user control over the tuning procedure
Proceedings of the 38th IEEE Conference on Decision and Control (Cat. No.99CH36304)
Presents a nonlinear extension of the ν-gap metric introduced in Vinnicombe (1993). Indeed, we pr... more Presents a nonlinear extension of the ν-gap metric introduced in Vinnicombe (1993). Indeed, we present an input-output version of the generalized stability margin and the ν-gap metric. The notion of image representation as presented in van der Schaft (1996) allows one to use these alternative definitions in a nonlinear context for the derivation of a robust stability theorem
Proceedings of the 1998 American Control Conference. ACC (IEEE Cat. No.98CH36207), 1998
We present a closed-loop parametric identification setup that allows the estimation of both the i... more We present a closed-loop parametric identification setup that allows the estimation of both the input-output and noise dynamics. The method is based on the minimization of a standard identification criterion and a parametrization that is tailored to the closed-loop configuration
In this paper, the family of algorithms presented previously by the authors (1999) is extended fo... more In this paper, the family of algorithms presented previously by the authors (1999) is extended for the identification of continuous time nonlinear plants operating in closed-loop. The main novelty is that the identification of unstable plants is covered in its generality
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