Abstract
The industrial processes that require the use of the web require a control system which allows for preserving the properties of the web unaltered, avoiding the risk of wrinkling, tearing, breakage and other defects. This control generally takes place by detecting the tension and the speed in certain points of the system since these variables determine the stress state on the web, which, if altered beyond certain ranges, can lead to the defects mentioned above. The problem of tension and web speed control is very demanding because the system’s dynamic is a function of many process variables that often vary over a wide range. In this study, an experimental system consisting of 12 rollers, four motorised, was analysed. This system was divided into four subsystems according to the logic of decentralised control. The tension of the initial and final subsystems and the speeds of the two central subsystems were monitored. This study proposes estimating continuous-time transfer functions using experimental time-domain data. A nonlinear least-squares search-based method minimises a weighted prediction error norm for directly identifying the mathematical model used to describe the web transport system. To test the performance of the proposed strategy, experimental data were collected in an open-loop configuration with constant voltage given to the four servo motors. The collected data were subsequently processed to define an extremely simple system model composed of a very limited number of parameters representing the system through transfer functions. The model was further validated by comparing the results obtained through simulations with the experimental data obtained with different inputs, and was also validated with some closed-loop tests.
Highlights
The term web is used to describe thin materials manufactured and processed in a continuous and flexible strip
Today many industrial processes employ webs, stored in the form of reels and moved by rollers, to mass produce a wide variety of products made from materials that are characterized by a continuous strip
The procedure here proposed for model identification considers that for a system such as the one analysed, the MIMO model Equation (9) includes transfer functions that, for the physical constitution of the system, have a different weight and importance for the system behaviour
Summary
The term web is used to describe thin materials manufactured and processed in a continuous and flexible strip. These approaches consider models consisting of an extremely limited number of parameters (generally two or three) and evaluate the validity of a model by comparing, for example, the response of the model and the real system to a step input These modelling methodologies use experimental data to directly identify a model with few parameters and are named data-driven techniques for identification. From the previous considerations, considering the development of robust control techniques applicable to dynamic models with uncertain parameters and the possibility of modelling in a simplified way by identifying the model from the experimental behaviour of the system, the present study dealt with experimentally testing the validity of models simplified for a multi-roller web transport platform. The proposed work’s main novelty consists in having tested the applicability of data-driven identification techniques of the dynamic model to an experimental platform with multiple rolls and different connected sections. This paper describes all the theoretical and experimental details and the results obtained
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