High quality galvanized steel strip is a need of today's manufacturers of various products. In particular, in the top quality section steel strips for the automotive, building and consumer goods industries only th...
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High quality galvanized steel strip is a need of today's manufacturers of various products. In particular, in the top quality section steel strips for the automotive, building and consumer goods industries only those steel producers will be successful who are applying state-of-the-art process technologies. For this reason, VOEST-ALPINE Industrieanlagenbau mbH (VAI) and VOEST-ALPINE Stahl Linz developed a new galvannealing control system to optimize this metallurgical process. As the latest improvement of the galvannealing control strategy, a neural network controller has been developed by VAI in Cooperation with the Vienna University of Technology Christian Doppler laboratory for Intelligent Control Methods for process Technologies. The paper describes the galvannealing process as far as it is necessary for the understanding of the controller functions, the controller structure and its essential functions. Furthermore, the neural network structure used and its integration into the controller system are explained. A discussion of simulation and practical operating results shows the improvements achieved by using a neural network controller in comparison to the conventional controller.
This paper deals with nonlinear predictive control based on higher order Takagi-Sugeno fuzzy systems which can also be interpreted as generalized radial basis function networks. We investigate how the fuzzy models can...
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This paper deals with nonlinear predictive control based on higher order Takagi-Sugeno fuzzy systems which can also be interpreted as generalized radial basis function networks. We investigate how the fuzzy models can be linked to a special type of model based predictive control algorithm, namely the dynamic matrix control (DMC). Previously, purely linear step response models were used for long-range prediction. Here, the method is extended to nonlinear processes. Therefore, various step responses for different operating points are extracted from the fuzzy model. For performance evaluation, a heat exchanger is identified by means of the local linear model tree algorithm and controlled by the modified DMC.
Predictive control algorithms are promising also in the case of nonlinear systems. Two versions of extended horizon predictive control algorithms are given here for the nonlinear simple Hammerstein model. A quadratic ...
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Predictive control algorithms are promising also in the case of nonlinear systems. Two versions of extended horizon predictive control algorithms are given here for the nonlinear simple Hammerstein model. A quadratic cost function is minimized, which considers the quadratic deviation of the reference signal and the output signal predicted in a future point and also the squares of the control increments. The system model is transformed to a predictive incremental form. Two versions of suboptimal extended horizon control algorithms are given with different assumptions for the control signal during the control horizon. Robustness properties of these algorithms are considered in case of plant-model mismatch through some simulation examples.
A third-order proportional process model with parameter uncertainty is controlled by different simple controllers. First the robustness of four different PID-control designs is investigated. Then internal model contro...
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A third-order proportional process model with parameter uncertainty is controlled by different simple controllers. First the robustness of four different PID-control designs is investigated. Then internal model control (IMC) is designed in the time domain for the exact process model and for its approximating model with a first-order lag and a delay time. Finally, the PID-control of the nominal model is extended by an IMC-like feedback, which makes the control especially robust.
The development of a reliable fault detection and isolation (FDI) scheme for nonlinear processes is often laborious and difficult to achieve due to the complexity of the system. Neural networks and fuzzy models, able ...
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The development of a reliable fault detection and isolation (FDI) scheme for nonlinear processes is often laborious and difficult to achieve due to the complexity of the system. Neural networks and fuzzy models, able to approximate nonlinear dynamic functions offer a powerful tool to cope with this problem. In this paper, a multi-model approach for FDI of sensor faults on a highly nonlinear real world processes is introduced. The approach is based local linear fuzzy models and provides residuals which are structured in a way that detection of six and isolation of five different sensor faults over all ranges of operation becomes possible. The approach enables on-line supervision of the process. Furthermore, a sensitivity analysis of the residuals to different faults can be made, based on the parameters of the fuzzy models.
An overview of presently known neural networks for the identification of nonlinear dynamic systems is given. The suitable networks are classified where two different approaches, the external and internal dynamic netwo...
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An overview of presently known neural networks for the identification of nonlinear dynamic systems is given. The suitable networks are classified where two different approaches, the external and internal dynamic networks, have to be distinguished. One alternative is to apply standard static neural networks and incorporate the dynamics by providing the network with information about previous inputs and outputs created by external linear filters. Another possibility is to include dynamic elements within the neural network structure and therefore making the network itself a nonlinear dynamic system. The principles, advantages and drawbacks of both approaches are pointed out. Two special neural network architectures, one with external and one with internal dynamics, are considered in more detail. Their capability to identify complex nonlinear dynamic real-world processes is studied. Experimental results for two multi-variable processes are shown, a combustion engine turbocharger and an industrial scale tubular heat exchanger.
In this paper, local linear fuzzy models are used for adaptive predictive control of nonlinear processes. First, an algorithm (LOLIMOT = local linear model tree algorithm) for off-line identification of Takagi-Sugeno ...
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In this paper, local linear fuzzy models are used for adaptive predictive control of nonlinear processes. First, an algorithm (LOLIMOT = local linear model tree algorithm) for off-line identification of Takagi-Sugeno type fuzzy models is briefly reviewed. In order to cope with time-variant nonlinear processes and also with the influence of non-measurable disturbances, an on-line adaptation of the model is performed. A recursive least-squares algorithm (RLS) is applied to update the linear parameters in the rule consequents locally. The local estimation results in low computational effort and avoids forgetting in non-active operating regimes. The effectiveness of the approach is demonstrated by simulations and by controlling the output temperature of a cross-flow heat exchanger.
The operation of technical processes requires increasingly advanced supervision and fault diagnosis to improve reliability, safety and economy. This paper describes structures for advanced methods of fault detection a...
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The operation of technical processes requires increasingly advanced supervision and fault diagnosis to improve reliability, safety and economy. This paper describes structures for advanced methods of fault detection and diagnosis. It begins with a consideration of a knowledge-based procedure which is based on analytical and heuristic information. Then different methods of fault detection are considered, which extract features from measured signals and use process and signal models. These methods are based on parameter estimation, state estimation and parity equations. By comparison with the normal behaviour, analytic symptoms are generated. Human operators may be a further source of information, and support the generation of heuristic symptoms. For fault diagnosis, all symptoms have to be processed in order to determine possible faults. This can be performed by classification methods or approximate reasoning, using probabilistic or possibilistic (fuzzy) approaches based on if-then-rules. The application of these methods is shown for the fault detection and diagnosis of Dieselengines.
In this paper methods for fault diagnosis of car components are presented. Model based methods like parameter estimation can be used for an estimation of the process coefficients. By dividing the nonlinear characteris...
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In this paper methods for fault diagnosis of car components are presented. Model based methods like parameter estimation can be used for an estimation of the process coefficients. By dividing the nonlinear characteristic curve into several sections good estimation results can be achieved and a diagnosis of the shock absorber be performed. Signal spectra estimation for detection of tire pressure loss requires only an accelerometer to measure the vertical acceleration of the wheel. The presented results were obtained with measured data drawn from a test rig and a driving car. The proposed methods are suited for an on-line supervision of the car as well as for technical inspection e.g. in workshops.
In this paper methods for fault detection and diagnosis of vehicle suspensions are presented. With parameter estimation and parity equations symptoms on the current process status can be extracted. By means of paramet...
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In this paper methods for fault detection and diagnosis of vehicle suspensions are presented. With parameter estimation and parity equations symptoms on the current process status can be extracted. By means of parameter estimation detailed symptoms can be generated, allowing an automatic distinction of different faults. For the automatic classification, neural networks were trained. Parity equations are well suited for a detection of sensor faults, although they do not offer the possibility for a distinction of different faults. All the presented results were obtained with measured data drawn from a test rig and a driving car. The proposed methods are suited for an on-line supervision of the car as well as for technical inspection e.g. in workshops.
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