Decentralized H∞ based control of a web transport system

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Updating of a lumped model for an experimental web tension control system using a multivariable optimization method’

The modelling and the control of web handling systems have been studied for a long time; correct modelling is necessary in order to design a better control system or to identify the plant parameters experimentally. On the web dynamics itself, lumped parameters expressions may be used to designate a web section between two adjacent drive rolls, and there is the necessity of incorporating the property of viscoelasticity to the web. In this paper the lumped model of a new web tension experimental system is updated; the model is based on the conservation mass, torque balance and viscoelasticity (Voigt approach). The experimental system consists of four sections each of which is driven by a servomotor; the speed and tension feedback, by using encoders and tension sensors, drives simultaneously the four servomotors through a real time C programmed D/A board. Usually, as described in the literature, these kinds of models are developed in the Laplace domain and the block scheme gives a graphical interpretation of the interaction between different sections. The transformation of the block scheme in a differential equation system in the time domain is fully described in this paper; it is not a simple step and it requires the introduction of not null initial condition for the derivative of physical variables. Moreover, the problem of validation has been dealt with in detail in this paper, considering simultaneously 2 different combinations of input data in open loop and a multivariable optimization method in order to estimate a certain number of unknown parameters. The results will show the accuracy of this kind of lumped parameters model for the complex experimental systems and useful information for successively designing an efficient control strategy

Detecting damage through the processing of dynamic shapes measured by a PSD-triangular laser sensor

There exist several studies in the literature which have shown the potentiality offered by certain vibration-based techniques aimed at detecting damage in structural systems. In all these existing techniques noise (distributed and/or outliers) plays a significant role and can make the difference between a successful or an unsuccessful application. In spite of such a mentioned remarkable influence, the studies aimed at investigating the influence of noise on the success of the techniques are not as rich in experimental details as they are in numerical simulations. In this work an extensive set of experiments aimed at evaluating the feasibility of certain diagnosing techniques is provided. This work should also be considered as the experimental validation of certain analytical and numerical simulations carried out in the past [Gentile, A., Messina, A., 2003. On the continuous wavelet transforms applied to discrete vibrational data for detecting open cracks in damaged beams. International Journal of Solids and Structures 40, 295–315; Messina, A., 2004. Detecting damage in beams through digital differentiator filters and continuous wavelet transforms. Journal of Sound and Vibration 272, 385–412] within the frame of real measurements based on a particular laser technology; in addition, the mentioned validating experiments illustrate certain peculiarities not shown in the past, and, finally, valuable benchmarks are provided for testing future diagnosing techniques in numerical simulations. The experimental set-up consists of both commercial and electronic circuits appropriately designed and realized, whose significance, in the measuring system is accurately described in order to increase the signal/noise ratio of the dynamical measurements