Jan Ogrodzki

Modeling of potentiometric sensors sensitive to ions of valency one and two for possible applications in WARMER project

This paper presents a novel model of potentiometric sensors sensitive to ions of valency one and two such as H+, K+, Na+, NH4+, Mg+, SO4-, NO3-, Cl- appearing in environmental water resources. The proposed models are based on the physical description by Van den Berg and behavioral description by Nikolsky and Eisenmann for ion-selective membranes. The elaborated models are applicable for data fusion algorithms which may be useful in the EU FP6 WARMER project dedicated to a system for water pollution risk management.

Transient analysis of circuits with ideal switches using charge and flux substitute networks

This contribution presents a new method for time-domain analysis of linear and nonlinear circuits with ideal switches controlled by internal circuit variables. At switching instants due to instantaneous changes of circuit topology instantaneous jumps of charge and flux occur if initial conditions before and after the switching instant are inconsistent. We propose a method for calculation of these jumps and of the initial conditions from dedicated charge and flux substitute networks based on charge and flux conservation laws.

Electrical properties of potentiometric sensors -an empirical study

The paper sums up investigations of electrical properties of potentiometric sensors that are under development in the EU FP6 WARMER project. There are 2 main goals of the empirical study: to determine minimum input resistance/bias current of data acquisition board and to determine the quality of analytical signal in DC and transient responses of the potentiometric sensors.

Macrosimulation of nonlinear dynamic systems for wave-shaping applications

Macromodeling is a technique widely used in circuits simulation. Macromodels usually describe complex, repetitive parts of large systems. They are often created on the base of original circuits by their simplification, e.g. macromodels of operational amplifiers. Another group of macromodels makes use of the circuit response approximation. This approach is called behavioral macromodeling. Low numerical complexity of behavioral macromodels is especially useful in CAD systems where circuit simulation must be run many times. In this paper the behavioral macromodeling technique has been applied to the whole circuit not to its part. This technique may be understood as shaping of the circuit output response and so belongs to a class of wave-shaping methods. We have used it to nonlinear, dynamic circuits with periodic signals of finite spectra, as e.g. in audio systems. The macromodels shape their frequency and spectral characteristics with a sufficient simplicity to omit unwanted distortions and with a sufficient efficiency to run the simulator in real time. Elaboration of this wave-shaping simulator is based on dynamic circuits identification, Fourier approximation of signals and harmonic balance technique. The obtained macromodel can be run as a software substitute for a hardware audio system.

Chemical Sensors for Water Monitoring -Diversity of Approaches to Behavioral Modeling

Mathematical models of chemo-electrical characteristics of ion-sensitive chemical sensors is essential for development of measuring algorithms to be implemented in firmware of water probes. A crucial point of algorithms like these is a data fusion task, where a matrix of sensors sensitive to a matrix of ions give a matrix of electrical responses. Hence unknown ion activities may be calculated if a parameterized mathematical model of sensor is known. During three years of activity in FP6 WARMER project a diversity of physical and behavioral approaches to sensors modeling has been considered. Since a model selection influence accuracy of measurements, then a plenty of different modeling approaches was discussed and practically verified on the base of laboratory measurements of sensors. Some typical measurements have been used and verification of accuracy of existing has been performed. This contribution contains a discussion of possibilities of modeling of potentiometric sensors. Several physical and behavioral models have been taken into account. It has been shown that in data fusion application essential is small number of parameters and small calculation complexity since accuracy of model has not to be better than accuracy of sensors which is rather low. Hence we must focus on a trade-off between necessity of accurate modeling and availability of accurate sensors.

Compact modelling in circuit simulation: the general purpose analyser "OPTIMA 3"

A behavioural modelling of elements becomes a standard in circuit simulators. In some of the expressions, device descriptions are mixed with the netlist (dispersed modelling). We propose a simulator OPTIMA 3, with a flexible style of device modelling by means of blocks of a behavioural description, called compact modelling.<<ETX>>

Numerical solution of stiff algebraic-differential systems with piecewise fixed step control

Computer analysis of nonlinear dynamic electronic s ystems requires solution of Ordinary Differential E quations (ODE) or Algebraic–Differential Equations (ADE). Since no nlinearities in these equations usually disable ana lytic l approaches, the only ones available are numerical, based on Dif ferentiation Formulae (DF). In physical sciences pr oblems of dynamics are often stiff, i.e. the shortest and the longest time constants have a ratio of many orders . Problems like this require numerical methods with a time step that var y in a wide range without any loss numerical stabil ity. In literature there are Numerical DF (NDF) and Backward DF (BDF) which have satisfactory stability properties for or ders from 1 to 5. To provide the best efficiency of the solution p rocess we select an order to provide an assumed lev el of Local Truncation Error (LTE) with as long step as possibl e. Selection of this step is based on LTE estimatio n during the solution process. While this estimation is availabl e with a good accuracy, accurate calculation of a n ew step is more difficult. Formulae joining the estimator with the step hold only in the constant step case, not when t step is variable. In this paper we propose a method where the step th ough variable is kept constant in a segment of step s o enable calculation of a new step from the constant step fo rmula. This approach has useful numerical propertie s.

Nonlinear dynamic macromodeling techniques for audio systems

This paper develops a modelling method and a models identification technique for the nonlinear dynamic audio systems. Identification is performed by means of a behavioral approach based on a polynomial approximation. This approach makes use of Discrete Fourier Transform and Harmonic Balance Method. A model of an audio system is first created and identified and then it is simulated in real time using an algorithm of low computational complexity. The algorithm consists in real time emulation of the system response rather than in simulation of the system itself. The proposed software is written in Python language using object oriented programming techniques. The code is optimized for a multithreads environment.

Analog approach to mixed analog-digital circuit simulation

Logic simulation of digital circuits is a well explored research area. Most up-to-date CAD tools for digital circuits simulation use an event driven, selective trace algorithm and Hardware Description Languages (HDL), e.g. the VHDL. This techniques enable simulation of mixed circuits, as well, where an analog part is connected to the digital one through D/A and A/D converters. The event-driven mixed simulation applies a unified, digital-circuits dedicated method to both digital and analog subsystems. In recent years HDL techniques have been also applied to mixed domains, as e.g. in the VHDL-AMS. This paper presents an approach dual to the event-driven one, where an analog part together with a digital one and with converters is treated as the analog subsystem and is simulated by means of circuit simulation techniques. In our problem an analog solver used yields some numerical problems caused by nonlinearities of digital elements. Efficient methods for overriding these difficulties have been proposed.

Time-domain simulation of integrated circuits with lossy nondispersive interconnects

In simulation of VLSI Integrated Circuits (ICs) that operate at considerably high frequencies essential is distributed modeling of interconnects. In this paper a study of algorithms is proposed dedicated to simulation of nonlinear ICs together with their interconnects which are modeled by means of lossy, nondispersive, in general also coupled transmission lines. A vector model of the coupled transmission lines is proposed and discussed. This model is efficiently applicable in transient analysis of ICs where cts with such solution techniques as sparse matrix, band matrix, iterative approach and mixed approach. Numerical complexity of these techniques is analyzed and compared and the best approach is selected. Several simulation results are shown.