2005 (Volume 15)
Identification of nonlinear systems and its application to Model Predictive Control
(Kumamoto Study Center of The University of The Air, c/o Sojo University, Japan)
(Faculty of Engineering, Kumamoto University, Japan)
This paper describes a new method for identifying and separating Volterra kernels of nonlinear control systems by use of pseudorandom M-sequence and correlation technique, and its application to model predictive control. By use of this identification method, we can obtain Volterra kernels of up to 3rd order of a nonlinear system. M-sequence is applied to a nonlinear system and the crosscorrelation function between the input and output is calculated. Then the crosscorrelation function includes all the crosssections of Volterra kernels of the nonlinear system. The problem is how to separate these crosssections from each other. This paper proposes two methods for separating these crosssections:one is the suitable selection of M-sequence and the other is amplitude variation method. This identification method is applied to nonlinear model predictive control. Computer simulations show that this method for identification and separation of Volterra kernels of nonlinear system is very effective for identifying nonlinear control systems and for its application to model predictive control of nonlinear system.
keywords: identification, nonlinear systems, Volterra kernels, Model Predictive Control, M-sequence.
Feedback and control cascade using seven - Level NPC voltage source inverter
(University of Sciences and Technology Houari Boumediene, Algérie)
|El-Madjid Berkouk and Mohamed Seghir Boucherit|
(Laboratoire de Commande des Processus, Département de Génie Electrique. Ecole Nationale Polytechnique d'Alger, Algérie)
In this paper, the authors present a study of the stability problem of the input DC voltages of the seven-level neutral point clamping (NPC) voltage source inverter (VSI). In the first part, a knowledge model of this converter is developed by using connection functions. In the second part, the authors propose aPWMstrategy which uses six bipolar carriers to control the converter. In this part, the inverter is fed by constant input DC voltages. In the last part of the paper, the authors study the stability problem of the input DC voltages of the inverter. Thus, a cascade is studied constituted by three two-level PWM rectifiers - clamping bridge - seven-level NPC VSI. The obtained results show that the input DC voltages of the inverter are not stable. To improve the performances of the proposed cascade and stabilize the input DC voltages, the authors propose in this paper a solution which uses a linear feedback control of this cascade. This study allows to find a solution for the instability problem of the input DC voltages of the inverter. The results obtained with this solution confirm a good performance of the system.
keywords: Seven-level, NPC inverter, clamping bridge, PWM rectifier, space vector, current hysteresis, feedback control.
Networked control system for a pitch-plane model of a magnetorheological suspension
(Department of Process Control, University of Science and Technology AGH Cracow, Poland)
(Department of Automatics, University of Science and Technology AGH Cracow, Poland)
The study is concerned with a networked control system (NCS) for vibration control in a two degree of freedom (2 DOF) pitch-plane model of a magnetorheological (MR) suspension. Pitch-plane model of MR suspension is described. The structure of the NCS utilizing a serial bus standard CAN (Controller Area Network) and 16-bit industrial microcontroller of the M16C6N family are characterized. Results of NCS experimental testing conducted in the pitch-plane model of MR suspension are provided.
keywords: networked control system, CAN bus, pitch-plane model, MR damper suspension.
A power system application of a robust decentralized controller design methodology
|Vojtech Veselý and Alena Kozáková|
(Department of Automatic Control Systems, Faculty of Electrical Engineering and IT, Slovak University of Technology, Slovak Republic)
The paper deals with the frequency domain design of a robust power system stabilizer (PSS) for a multivariable power system. The proposed PSS design procedure is based on a novel approach that applies the independent design methodology along with the well-known small gain theory and the robust stability conditions in the M-D setup to the so-called equivalent subsystems . Theoretical results have been applied to the design of a robust multivariable PSS for a part of the Power System of the Slovak Republic.
keywords: design methodology, multivariable systems, power system stability, robustness.
Application of reduced order phenomenological model to pH nonlinear control
|Krzysztof Stebel and Mieczys³aw Metzger|
(Institute of Automatic Control, Silesian University of Technology, Poland)
Changes in process sensitivity with pH make the design of the conventional controllers difficult. pH processes are very hard to control because of strong nonlinearity and usually time varying characteristics. A lot of work has been done in the field of phenomenological modelling of the pH processes. However, there is a need to simplify the model to have it suitable for control purposes. This follows from the fact that the internal model for the controllers must be as simple as possible. Wiener models consisting of a linear dynamic element followed by a static nonlinear element are considered to be perfect to represent a wide range of nonlinear processes. The proposed reduced order phenomenological model of pH has a similar form as the Wiener models but includes bilinear reduced order phenomenological dynamic element. This model was validated using the real world pilot plant. The possibility of combining the phenomenological and arbitrary approaches occurred. The aim of this paper is to present reduced order model of pH process which can be used for simulation purposes and to design process model based controller.
keywords: pH processes, nonlinear systems, input-output linearization, pH control, model based control, reduced order models polynomial approximation.
Modelling, simulations and experimental investigation of a hybrid, electrofluid vehicle suspension
|Roman Korzeniowski, Janusz Kowal and Janusz Pluta|
(Department of Process Control, AGH University of Science and Technology, Poland)
The paper summarises the structure, analysis and testing of novel hybrid suspension, accommodating a cascade combination of two vibration isolators: an active electrohydraulic and a semiactive electropneumatic one. The developed mathematical model of a hybrid suspension supported by the simulation data are utilized in the synthesis of an adaptive control system with the reference model. Experimental tests performed for the purpose of verification demonstrate the good performance of the newly developed suspension.
keywords: vehicle suspension, fluid power, adaptive control, modeling, simulation, experimental test.
Self balancing rotor design - simulation and experimental validation
|Micha³ Manka and Tadeusz Uhl|
(Department of Robotics and Machine Dynamics Faculty of Mechanical Engineering and Robotics University of Science and Technology AGH Cracow, Poland)
The paper deals with automatic balancing of rotating systems during operation. After discussion of existing techniques the novel concepts of balancing mechanisms are presented. The proposed method are easy to apply to various rotating devices, with no need of machine construction modification. Next basics of active balancing control algorithms are presented, and designed detection and correction algorithms are discussed. After descriptions of mechanisms, measurement and control algorithms, simulation and experimental results are presented. The paper ends some conclusions about presented active balancing mechanisms and further works directions are presented.
keywords: balancing, active control, automatic balancing, rotating systems.