Krzysztof B. Janiszowski

A modification and the Tustin approximation

The Tustin approximation for determining a discrete-time representation of a continuous-time control system is sufficiently precise. If a sampling interval is chosen properly, it results in some errors in time responses of a plant model, though they are not critical and the static gain value is the same as in the original transfer function. However, this method generally increases the number of coefficients in the numerator of the approximate discrete-time transfer function by one in comparison with the exact transformation. A simple modification of the Tustin approximation that does not have this disadvantage and is far more precise than the original approximation is presented. The additional numerical effort is negligible. Examples of the transformation for three simple continuous systems are presented. >

Approximation of a linear dynamic process model using the frequency approach and a non-quadratic measure of the model error

Abstract The paper presents a novel approach to approximation of a linear transfer function model, based on dynamic properties represented by a frequency response, e.g., determined as a result of discrete-time identification. The approximation is derived for minimization of a non-quadratic performance index. This index can be determined as an exponent or absolute norm of an error. Two algorithms for determination of the approximation coefficients are considered, a batch processing one and a recursive scheme, based on the well-known on-line identification algorithm. The proposed approach is not sensitive to local outliers present in the original frequency response. Application of the approach and its features are presented on examples of two simple dynamic systems.

Application of a PExSim for modeling a POLVAD artificial heart and the human circulatory system with left ventricle assistance

Application of a PExSim for modeling a POLVAD artificial heart and the human circulatory system with left ventricle assistance This paper presents a model of the human circulatory system with the possible addition of a parallel assist device, which was developed for the purpose of artificial heart monitoring. Information about an identification experiment of an extracorporeal ventricle assist device POLVAD is included. The modelling methods applied and the corresponding functional blocks in a PExSim package are presented. The results of the simulation for physiological conditions, left ventricle failure and pathological conditions with parallel assistance are included.

Identification of parametric models with a priori knowledge of process properties

Abstract An approach to estimation of a parametric discrete-time model of a process in the case of some a priori knowledge of the investigated process properties is presented. The knowledge of plant properties is introduced in the form of linear bounds, which can be determined for the coefficient vector of the parametric model studied. The approach yields special biased estimation of model coefficients that preserves demanded properties. A formula for estimation of the model coefficients is derived and combined with a recursive scheme determined for minimization of the sum of absolute model errors. The estimation problem of a model with known static gains of inputs is discussed and proper formulas are derived. This approach can overcome the non-identifiability problem which has been observed during estimation based on measurements recorded in industrial closed-loop control systems. The application of the proposed approach to estimation of a model for an industrial plant (a water injector into the steam flow in a power plant) is presented and discussed.

Modelling and Simulation of coronary circulation system

The paper presents a new numerical package for modelling and simulation of human circulatory system with an extension of coronary circulation model. The main aim of addition of the coronary model was to allow simulation and verification of the influence of the left ventricle assistance on the coronary flow conditions and the possibility of simulation of the coronary vessels occlusion. The whole package was implemented as a part of PExSim (Process Explorer and Simulation) application. As a result we have the useful tool, which gives an opportunity to study functions of individual components of the human circulatory system as well as the system as whole. It allows for simulation of proper and pathology circulation conditions, such as left or right heart failure. Implemented model of the ventricle assist device (VAD) gives the opportunity for modelling the influence of the heart assistance on the coronary flows and the imminent myocardial infarction conditions. Applied methods and the modelling data sets are presented. Analysis and comparison of the received results are included.

Low air consumption control in pneumatic positioning system

Abstract The paper presents an idea of an open-loop control of a pneumatic positioning system consisting of a pneumatic cylinder, inexpensive measurement system and four on-off switching valves. A strategy of four pulses on-off control trajectory for implementation of a determined piston displacement without an overshoot is presented. Parameters for the control are determined by the application of artificial neural nets that have to be trained before the application. The strategy is nearly time-optimum one and results in a short control time, a quiet valves action and a significant reduction of the compressed air consumption in the comparison to algorithms used in pneumatic positioning systems. This way of control was investigated in many simulation experiments and in tests performed in a laboratory as well. It can be a basis for construction and development attractive, low-cost, economic pneumatic positioning systems.

Towards Estimation in the Sense of the Least Sum of Absolute Errors

Abstract This paper presents an attempt to introduce an estimation algorithm that can lead to estimates of coefficients of a parametric model, close to the values detennined by the Least Sum of Absolute errors of the model output. Examples of LSA-estimation application presented here show specific and interesting features. This estimation is quite insensitive to instantaneous, even very powerful and non-symmetric disturbances. A theorem for the derivation the LSA-estimation algorithm, as a special modification of the weighted Least Sum of Square estimation is presented. Application of the LSA-algorithm and a comparison with LSS-estimation results is presented on examples of static and dynamic models of linear plants.

State Space Adaptive Control for Nonlinear Systems

Abstract In education of modern control theory it is very substantial to present students technical problems where the application of modern methods is necessary and justified by their complexity and present this in a control lab. An example of a control system where it is advisable to apply; a state space controller with observer, an adaptive design of controller algorithm with on-line identification, a compensation of nonlinearity and processing of disturbed data with serious real-time processing problems is necessary for adaptive positioning of computer controlled pneumatic drive. All these problems can be presented in real scale in any lab for automatic control, where pneumatic systems are investigated.

Automatic control system for ventricular assist device

This paper presents a research and some results of experiments at development of an automatic control system for the heart assist device. The aim of the study was to develop and design a new control system for the pneumatic control unit in a heart assisting device. The new algorithm is based on diagnostic tests which are used to detect full ejection and complete filling states of the artificial chamber. To facilitate a more in-depth understanding of the implemented algorithm and its features, a brief description of the IT solutions which have been applied is given.

Modification of human circulatory system model for the purpose of physical reproduction of apex of the heart conditions

The paper presents the proposition of a numerical model of the human circulatory system modification for the purpose of physical reproduction of conditions prevailing in the apex of the heart on a hybrid simulator. This is a physical-numerical stand which performs a generation of hydraulic conditions occurring in the selected points of circulatory system. However, so far, there was no possibility of reproduction the apex of the heart point. The paper presents the nature of the problem and suggest solution. The results of simulation tests and analysis of assumptions correctness are shown. Description of further development works is included.