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1
Content available remote Supervisory predictive control and on-line set-point optimization
100%
Tatjewski P.
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2010
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tom Vol. 20, no 3
483-495
EN
The subject of this paper is to discuss selected effective known and novel structures for advanced process control and optimization. The role and techniques of model-based predictive control (MPC) in a supervisory (advanced) control layer are first shortly discussed. The emphasis is put on algorithm efficiency for nonlinear processes and on treating uncertainty in process models, with two solutions presented: the structure of nonlinear prediction and successive linearizations for nonlinear control, and a novel algorithm based on fast model selection to cope with process uncertainty. Issues of cooperation between MPC algorithms and on-line steady-state set-point optimization are next discussed, including integrated approaches. Finally, a recently developed two-purpose supervisory predictive set-point optimizer is discussed, designed to perform simultaneously two goals: economic optimization and constraints handling for the underlying unconstrained direct controllers.
2
Content available Offset-free nonlinear Model Predictive Control with state-space process models
100%
Tatjewski P.
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tom Vol. 27, no. 4
595--615
EN
Offset-free model predictive control (MPC) algorithms for nonlinear state-space process models, with modeling errors and under asymptotically constant external disturbances, is the subject of the paper. The main result of the paper is the presentation of a novel technique based on constant state disturbance prediction. It was introduced originally by the author for linear state-space models and is generalized to the nonlinear case in the paper. First the case with measured state is considered, in this case the technique allows to avoid disturbance estimation at all. For the cases with process outputs measured only and thus the necessity of state estimation, the technique allows the process state estimation only - as opposed to conventional approach of extended process-and-disturbance state estimation. This leads to simpler design with state observer/filter of lower order and, moreover, without the need of a decision of disturbance placement in the model (under certain restrictions), as in the conventional approach. A theoretical analysis of the proposed algorithm is provided, under applicability conditions which are weaker than in the conventional approach. The presented theory is illustrated by simulation results of nonlinear processes, showing competitiveness of the proposed algorithms.
3
Content available Disturbance modeling and state estimation for offset-free predictive control with state-space process models
100%
Tatjewski P.
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2014
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tom Vol. 24, no. 2
313--323
EN
Disturbance modeling and design of state estimators for offset-free Model Predictive Control (MPC) with linear state-space process models is considered in the paper for deterministic constant-type external and internal disturbances (modeling errors). The application and importance of constant state disturbance prediction in the state-space MPC controller design is presented. In the case with a measured state, this leads to the control structure without disturbance state observers. In the case with an unmeasured state, a new, simpler MPC controller-observer structure is proposed, with observation of a pure process state only. The structure is not only simpler, but also with less restrictive applicability conditions than the conventional approach with extended process-and-disturbances state estimation. Theoretical analysis of the proposed structure is provided. The design approach is also applied to the case with an augmented state-space model in complete velocity form. The results are illustrated on a 2 x 2 example process problem.
4
Content available remote Nonlinear predictive control based on neural multi-models
63%
Ławryńczuk M. , Tatjewski P.
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2010
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tom Vol. 20, no 1
7-21
EN
This paper discusses neural multi-models based on Multi Layer Perceptron (MLP) networks and a computationally efficient nonlinear Model Predictive Control (MPC) algorithm which uses such models. Thanks to the nature of the model it calculates future predictions without using previous predictions. This means that, unlike the classical Nonlinear Auto Regressive with eXternal input (NARX) model, the multi-model is not used recurrently in MPC, and the prediction error is not propagated. In order to avoid nonlinear optimisation, in the discussed suboptimal MPC algorithm the neural multi-model is linearised on-line and, as a result, the future control policy is found by solving of a quadratic programming problem.
5
Content available remote Actuator fault tolerance in control systems with predictive constrained set-point optimizers
63%
Marusak P. M. , Tatjewski P.
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tom Vol. 18, no 4
539-551
EN
Mechanisms of fault tolerance to actuator faults in a control structure with a predictive constrained set-point optimizer are proposed. The structure considered consists of a basic feedback control layer and a local supervisory set-point optimizer which executes as frequently as the feedback controllers do with the aim to recalculate the set-points both for constraint feasibility and economic performance. The main goal of the presented reconfiguration mechanisms activated in response to an actuator blockade is to continue the operation of the control system with the fault, until it is fixed. This may be even long-term, if additional manipulated variables are available. The mechanisms are relatively simple and consist in the reconfiguration of the model structure and the introduction of appropriate constraints into the optimization problem of the optimizer, thus not affecting the numerical effectiveness. Simulation results of the presented control system for a multivariable plant are provided, illustrating the efficiency of the proposed approach.
6
Content available remote An infinite horizon predictive control algorithm based on multivariable input-output models
63%
Ławryńczuk M. , Tatjewski P.
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2004
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tom Vol. 14, no 2
167-180
EN
In this paper an infinite horizon predictive control algorithm, for which closed loop stability is guaranteed, is developed in the framework of multivariable linear input-output models. The original infinite dimensional optimisation problem is transformed into a finite dimensional one with a penalty term. In the unconstrained case the stabilising control law, using a numerically reliable SVD decomposition, is derived as an analytical formula, calculated off-line. Considering constraints needs solving on-line a quadratic programming problem. Additionally, it is shown how free and forced responses can be calculated without the necessity of solving a matrix Diophantine equation.
7
Content available remote Effective dual-mode fuzzy DMC algorithms with on-line quadratic optimization and guaranteed stability
63%
Marusak P. M. , Tatjewski P.
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tom Vol. 19, no 1
127-141
EN
Dual-mode fuzzy dynamic matrix control (fuzzy DMC-FDMC) algorithms with guaranteed nominal stability for constrained nonlinear plants are presented. The algorithms join the advantages of fuzzy Takagi-Sugeno modeling and the predictive dual-mode approach in a computationally efficient version. Thus, they can bring an improvement in control quality compared with predictive controllers based on linear models and, at the same time, control performance similar to that obtained using more demanding algorithms with nonlinear optimization. Numerical effectiveness is obtained by using a successive linearization approach resulting in a quadratic programming problem solved on-line at each sampling instant. It is a computationally robust and fast optimization problem, which is important for on-line applications. Stability is achieved by appropriate introduction of dual-mode type stabilization mechanisms, which are simple and easy to implement. The effectiveness of the proposed approach is tested on a control system of a nonlinear plant-a distillation column with basic feedback controllers.
8
Content available remote Stability analysis of nonlinear control systems with unconstrained fuzzy predictive controllers
63%
Marusak P. , Tatjewski P.
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tom Vol. 12, no. 3
267-288
EN
Stability analusis of nonlinear control systems with unconstrained fuzzy predictive controllers using input-output plant models (e.g. DMC, GPC) and nonlinear plants with delays is discussed in the paper. The idea is precisely explained using an example of control systems with fuzzy DMC (FDMC) controllers. The considered FDMC controller is based on analytical formulation of the DMC predictive control algorithm and Takagi-Sugeno fuzzy modeling. The atability analysis of the closed-loop nonlinear control system is based on a transformation of its description to the appropriate stste-space form. Theh the Tanaka-Sugeno stability criterion can be applied, consisting in solving a set of Lyapunov-type inequalities. The design procedure including the stability analysis is illustrated on examples.
9
Content available remote Soft computing in model-based predictive control
63%
Tatjewski P. , Ławryńczuk M.
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2006
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tom Vol. 16, no 1
7-26
EN
The application of fuzzy reasoning techniques and neural network structures to model-based predictive control (MPC) is studied. First, basic structures of MPC algorithms are reviewed. Then, applications of fuzzy systems of the Takagi-Sugeno type in explicit and numerical nonlinear MPC algorithms are presented. Next, many techniques using neural network modeling to improve structural or computational properties of MPC algorithms are presented and discussed, from a neural network model of a process in standard MPC structures to modeling parts or entire MPC controllers with neural networks. Finally, a simulation example and conclusions are given.
10
Wariantowa struktura regulacji z przełączającym algorytmem diagnostycznym w układz.e regulacji temperatury pary kotła energetycznego
63%
Plamowski S. , Tatjewski P.
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tom R. 51, nr 9 bis
267--269
PL
Artykuł opisuje koncepcje i rezultaty wdrożenia zaawansowanego predykcyjnego układu regulacji temperatury pary w kotle energetycznym w strukturze wariantowej. W pracy zaprezentowano opis techniczny obiektu wraz z istniejącą klasyczną strukturą regulacji oraz sposób włączenia struktury zaawansowanej. Zwrócono uwagę na podstawowe aspekty takie jak: bezpieczeństwo pracy nowoczesnych układów, przekonania kadry oraz kluczowe zagadnienie, jakim jest problem niepewności modelu. Zagadnienie niepewności modelu i sposoby jej wykrywania stanowią kluczowy temat tej pracy.
EN
This paper presents concepts and results o fan industrial application of advanced control in a switching structure where classic PID control layer is installed already. The DMC predictive control algorithm has been installed as a steam temperatures controller in the boiler. The authors present technical description of the boiler with classic control structure and the way of applying the DMC algorithm. The authors focused on the safety aspect of this advanced control structure. The problem of quality of control when model is uncertain was investigated. The diagnostic method was invented lor detection when the model is inadequate. Based on this diagnostic method switching control structure was tested and results of investigations arc presented in the paper.
11
Content available remote Multivariable CRHPC (constrained receding-horizon predictive control) algorithm with improved numerical properties
63%
Ławryńczuk M. , Tatjewski P.
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tom Vol. 13, no. 1
59-79
EN
This paper is concerned with the stabilising constrained receding-horizon predictive control algorithm (CRHPC) for multivariable processes. The optimal inputprofile is calculated by means of a new method the purpose of witch is to avoid inverting usually ill-conditioned matrices. additionally, ralatively simple formulae for calculating free and forced output predictions for the ARX process model, as well as the analytical stabilising control law in the unconstained case are derived, without the necessity of solving a matrix Diophantine equation.
12
Content available Współdziałanie regulacji predykcyjnej i bieżącej optymalizacji punktu pracy w strukturach sterowania z modelami Wienera
51%
Ławryńczuk M. , Marusak P. , Tatjewski P.
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2010
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tom R. 14, nr 2
470-480
PL
Numerycznie efektywne struktury sterowania alternatywne do klasycznej, warstwowej struktury sterowania są przedmiotem badań. W pierwszej strukturze dodano pomocnicze, liniowe zadanie optymalizacji punktu pracy. W drugiej strukturze, zadania optymalizacji punktu pracy i regulacji predykcyjnej są integrowane w jednym zadaniu optymalizacji kwadratowej. Użycie w tych strukturach modelu Wienera dodatkowo je upraszcza dzięki możliwości łatwego otrzymania liniowych aproksymacji dynamiki i statyki procesu.
EN
Two numerically efficient control system structures alternative to the classical one are considered. In the first one the supplementary Steady State Target Optimization (SSTO) is performed at each sampling instant. In the second one set-point optimization and predictive control are integrated into one optimization task. In the proposed approaches, thanks to using a Wiener process model, both predictive control and set-point optimization problems are simplified. Using the nonlinear model a linear dynamic and linear static approximations are easily obtained and used both for set-point optimization and predictive control.
13
Content available Struktury i algorytmy współdziałania regulacji predykcyjnej i bieżącej optymalizacji ekonomicznej
51%
Ławryńczuk M. , Marusak P. , Tatjewski P.
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tom R. 53, nr 10
55-61
PL
Celem pracy jest omówienie zagadnienia współpracy algorytmów regulacji predykcyjnej z nieliniową optymalizacją ekonomiczną. Problem ten jest szczególnie istotny wówczas, gdy dynamika zmian zakłóceń jest porównywalna z dynamiką procesu, ponieważ zastosowanie klasycznej warstwowej (hierarchicznej) struktury sterowania z rzadko powtarzaną optymalizacją ekonomiczną może nie być efektywne. Omawiane są dwie klasy struktur. W pierwszym przypadku stosuje się pomocniczą optymalizację ekonomiczną, której zadaniem jest aktualizacja punktu pracy poprzedzająca każdą interwencję algorytmu regulacji predykcyjnej. W dodatkowym liniowym lub kwadratowym zadaniu optymalizacji ekonomicznej stosuje się aktualizowaną na bieżąco liniową, liniowo-kwadratową lub odcinkowo-liniową aproksymację modelu. W drugim przypadku zadanie optymalizacji ekonomicznej i algorytm regulacji predykcyjnej są zintegrowane w pojedynczym problemie optymalizacji. Aby ograniczyć nakład obliczeń stosuje się aktualizowaną na bieżąco liniową lub liniowo-kwadratową aproksymację modelu, dzięki czemu otrzymuje się zadanie optymalizacji ekonomicznej w postaci problemu programowania kwadratowego.
EN
The paper is concerned with co-operation of model predictive control (MPC) algorithms with nonlinear economic optimisation. The problem is particularly important when dynamics of disturbances is comparable with dynamics of the process itself, since in such cases application of the classical multilayer (hierarchical) structure with infrequent economic optimisation may be not efficient. Two classes of control structures are investigated. In the first class an additional simplified optimisation is used which recalculates the operating point as frequently as the MPC controller executes. In the supplementary linear or quadratic programming optimisation problem approximate linear, linear-quadratic (updated on-line) or piecewise-linear models of the process are used. In the second class the economic optimisation and MPC manipulated variables computational load, approximate linear or linear-quadratic (updated on-line) models are used, then the resulting optimisation problem is of quadratic programming type.
14
Content available remote Design and Stability of Fuzzy Logic Multi-Regional Output Controllers
51%
Domański P. , Brdyś M. A. , Tatjewski P.
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tom Vol. 9, no 4
883-897
EN
Design and stability analysis of fuzzy multi-regional digital controllers is considered in the paper. The controllers are based on a notion of NARMAX systems, very similar to the Takagi-Sugeno fuzzy model. The nonlinear system is approximated by a number of linear subsystems. Linear controllers are designed for all subsystems. It can be made in a classical way due to the subsystems linearity. The controllers are blended into one controller by employing fuzzy logic, the result being the fuzzy multi-regional controller (FuMR). The stability analysis of nonlinear systems with FuMR controllers composed of dynamic output feedback local linear controllers is provided. Examples illustrate the design procedure and the meaning of the stability criterion.
15
Content available remote Cooperation of model predictive control with steady-state economic optimisation
51%
Ławryńczuk M. , Marusak P. M. , Tatjewski P.
Control and Cybernetics
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2008
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tom Vol. 37, no 1
133-158
EN
The problem of cooperation of Model Predictive Control (MPC) algorithms with steady-state economic optimisation is investigated in this paper. It is particularly important when the dynamics of disturbances is comparable with the dynamics of the process, since in such a case the classical hierarchical multilayer structure is likely to be not efficient and give the economic yield smaller than expected. This is because the economic nonlinear optimisation problem cannot be then solved on-line to update the optimal operating point as frequently as needed. On the other hand, simple target set-point optimisation based on linear models can be also insufficiently accurate. This paper introduces approximate formulations of the target set-point optimisation problem which tightly cooperates with the MPC and is solved as frequently as the MPC controller executes. Linear, linear-quadratic and piecewise-linear formulations are discussed, tuning guidelines are also given.
16
Content available remote Fail-bounded implementations of the numerical model predictive control algorithms
45%
Gawkowski P. , Lawryńczuk M. , Marusak P. , Sosnowski J. , Tatjewski P.
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tom Vol. 39, no 4
1117-1134
EN
Methods of fault-hardening software implementations of the numerical Model Predictive Control (MPC) algorithms are discussed in the paper. In particular, Generalized Predictive Control (GPC) algorithms are considered. The robustness of these algorithms with respect to faults is crucial for process safety and economic efficiency, as faults may result in major control performance degradation or even destabilization. Therefore, fault-hardening of GPC algorithms is an important issue. The fault sensitivity of the non-fault-hardened algorithms implementations and the effectiveness of the fault hardening procedures are verified in experiments with a software implemented fault injector. These experiments refer to the control system of a chemical plant. Experience with fault simulations resulted in some methods of fault-hardening which are described in detail. Improvement of the dependability of the GPC algorithms is commented for each of the proposed fault-hardening mechanism.
17
Content available remote Wpływ sterowania elektronicznym zaworem rozprężnym i wydajnością sprężarki na parametry pracy pompy ciepła typu powietrze-woda
38%
Rubik M. , Ziętek P. , Tatjewski P. , Marusak P. , Ławryńczuk M. , Szumski M. , Szumski M.
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tom T. 49, nr 10
404--410
PL
W ostatnich latach w Polsce zaobserwować można rosnące zainteresowanie pompami ciepła. Szczególnie duży wzrost dotyczy rynku pomp ciepła typu powietrze-woda, czego przyczyną mogą być malejące ceny oraz brak konieczności wykonywania instalacji dolnego źródła ciepła. Efektywność pompy ciepła maleje wraz ze wzrostem różnicy temperatury pomiędzy dolnym i górnym źródłem ciepła, stąd w przypadku powietrznych pomp ciepła, szczególnie celowe wydaje się dążenie do udoskonalenia działania urządzenia i zmniejszenia zapotrzebowania na energię napędową. Nowoczesne pompy ciepła typu powietrze/woda są zazwyczaj wyposażane w elektroniczny zawór rozprężny oraz wysokosprawne sprężarki sterowane inwerterowo. Właściwe płynne sterowanie otwarciem zaworu rozprężnego oraz wydajnością sprężarki wydaje się być jedną z kluczowych kwestii do rozwiązania w celu osiągnięcia maksymalnej efektywności energetycznej sprężarkowych pomp ciepła typu powietrze-woda. W artykule przedstawiono dane dotyczące rynku pomp ciepła w Polsce. Poruszono zagadnienie efektywności energetycznej urządzeń z uwzględnieniem wpływu sterowania elektronicznym zaworem rozprężnym oraz wydajnością sprężarki. Opisano stanowisko badawcze, które zostało zaprojektowane i wykonane w celu przeprowadzenia badań sprężarkowej pompy ciepła typu powietrze-woda i opracowania regulatora, którego zadaniem byłaby minimalizacja zużycia energii przez urządzenie. Przedstawiono wyniki badań obrazujące zmiany parametrów pracy pompy ciepła będące rezultatem sterowania zaworem i sprężarką oraz opisano wiele spostrzeżeń i problemów technicznych, jakie wystąpiły w trakcie prowadzenia prac badawczych. Przeprowadzone badania i analizy potwierdziły, że kluczową rolę w zapewnieniu prawidłowej pracy pompy ciepła odgrywa właściwe sterowanie otwarciem zaworu rozprężnego oraz prędkością obrotową wału napędowego sprężarki.
EN
In Poland increasing interest in the heat pumps is observed last years. A particularly large is increase in the air-water heat pumps market. The reason can be a lower price and no need to execute the heat source installation. Heat pump efficiency decreases together with the increase of difference between the heat source temperature and the heat sink temperature, therefore in the case of the air to water heat pumps it is especially important to strive to improve the operation of the units and to reduce the energy consumption. Modern air-to-water heat pumps are usually equipped with an electronic expansion valve and high efficiency inverter compressor. Proper continuous control of the expansion valve opening and the compressor performance seems to be one of the key issue to solve in order to achieve maximum energy efficiency of the compressor type air-to-water heat pumps. The article presents current data on the heat pump market in Poland. The issues of energy efficiency taking into account the impact of electronic expansion valve and compressor speed control are discussed. The test stand designed and executed in order to test the air-to-water heat pump and to develop the controller minimizing the energy consumption was described. The results of test showing the changes of parameters of the heat pump caused by the expansion valve and compressor control were presented. In addition a number of observations and technical problems, which occurred in the course of research were described. Research and analyses confirmed that a key role in ensuring the correct and efficient operation of the heat pump plays a proper control of the expansion valve and the speed of the compressor.
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