David M. Auslander

Control systems engineering education

This comprehensive article deals with the important field of control systems engineering education. Efforts have been made to present some historical perspectives, major concepts and thoughts on a practical curriculum when this field is viewed as a discipline. Also discussed are curricular issues including typical laboratory systems with emphasis on the role of simulation, logic and sequencing, and real-time simulation. An elaborate section is devoted to CACE software, its role in teaching and learning, potential shortfalls, and trends in software development and use. Views from industry are sought in terms of desirable skills in the practicing engineer and continuing education needs. A survey of a few academic programs and a complete list of textbooks in control over the past three decades appear in the appendices.

Dynamics of interacting populations

Abstract A biological population can be viewed as a distributed parameter dynamical system. The dynamics of host-parasite systems are investigated by coupling populations via age specific interactions; analysis and simulation results are compared with experiments performed on a laboratory ecosystem. A number of novel dynamical effects emerge from the model which have some interesting ecological consequences.

A 3-axis force balanced accelerometer using a single proof-mass

This paper presents a new method for wideband force balancing a proof-mass in multiple axes simultaneously. Capacitive position sense and force feedback are accomplished using the same air-gap capacitors through time multiplexing. Proof of concept is experimentally demonstrated with a single-mass monolithic surface micromachined 3-axis accelerometer.

Freeway ramp control using fuzzy set theory for inexact reasoning

Abstract This paper presents a fuzzy controller for freeway ramp metering, which uses rules of the form: IF “freeway condition” THEN “control action.” The controller has been designed to consider varied levels of congestion, a downstream control area, changing occupancy levels, upstream flows, and a distributed detector array in its rule base. Through fuzzy implication, the inference of each rule is used to the degree to which the condition is true. Using a dynamic simulation model of conditions0fj at the San Francisco-Oakland Bay Bridge, the action of the fuzzy controller is compared to the existing “crisp” control scheme, and an idealized controller. Tests under a variety of scenarios with different incident locations and capacity reductions show that the fuzzy controller is able to extract 40 to 100% of the possible savings in passenger-hours. In general, the fuzzy algorithm displays smooth and rapid response to incidents, and significantly reduces the minute-miles of congestion.

Direct digital process control: Practice and algorithms for microprocessor application

Process control applications and control algorithms suited for microprocessors are surveyed. Applications are noted both in large, general purpose process control systems and in specialized applications that have been made possible by the availability of computing power in small packages. Distributed control and use of extended data buses (data highways), both made possible by extensive use of microprocessors, are becoming standard in general purpose systems. General purpose process control systems still utilize proportional-integral-derivative (PID) algorithms and variants of them for the most part. Some recent research results on algorithms designed for use in stand-alone, single-loop calculator or microprocessor-based controllers are presented. These algorithms, which could also be used in direct digital control (DDC) systems, are specifically tailored for simple implementation in a relatively low computing power, discrete-time environment.

Random evolutionarily stable strategies.

Abstract The game-theoretic notion of competitive equilibrium has frequently been used to evaluate evolutionary trends. These discussions have centered mostly on the static situation, ignoring the constraints of Mendelian genetics. In this paper we illustrate by an example that, when population and genetic dynamics are included in a model, the outcome in a competitive situation can be quite different from that deduced from the corresponding static model. In particular, the nonlinearities due to density and frequency dependence can produce chaotic dynamics whose statistical properties may or may not fluctuate about the static “evolutionary stable strategy.”

Velocity estimation from widely spaced encoder pulses

It is often necessary to estimate the velocity of mechanical systems from the output of a digital encoder. Due to cost and/or noise problems, there maybe no direct velocity measurement available on such systems. Velocity reversal and sparseness of encoder signals are not handled well by traditional estimators. This paper proposes a transition logic based switching algorithm and an asynchronous multirate Luenberger observer based estimator to reduce these problems.

Fractionated Electrograms From a Computer Model of Heterogeneously Uncoupled Anisotropic Ventricular Myocardium

BACKGROUND The relation between heterogeneously coupled myocardium and fractionated electrograms is incompletely understood. The purpose of this study was to use a detailed computer model of nonuniformly anisotropic myocardium to test the hypothesis that spatial variation of morphology of electrograms recorded simultaneously from multiple sites increases with increasing heterogeneity of intercellular coupling. METHODS AND RESULTS A sheet of elements with Beeler-Reuter ionic kinetics was coupled with cytoplasmic resistivity to model cells. Gap junctional resistance values were assigned by recursive randomization to produce a fractal pattern of heterogeneous coupling, simulating damage resulting from infarction. The correlation dimension of the pattern, D, measured heterogeneity of intercellular coupling. The peak-to-peak amplitude, duration, minimum derivative (steepest downslope), number of inflections, frequency of peak power, and bandwidth of unfiltered unipolar electrograms were calculated. Linear regressions indicate (P < .001) that the coefficient of variation of five electrogram metrics increases with increasing substrate heterogeneity and that the distance over which electrogram morphology decorrelates decreases with increasing heterogeneity of intercellular coupling. CONCLUSIONS These findings confirm our hypothesis that the spatial variation of morphology of electrograms recorded simultaneously from multiple sites increases with increasing heterogeneity of intercellular coupling.

Deconvolution: A Novel Signal Processing Approach for Determining Activation Time From Fractionated Electrograms and Detecting Infarcted Tissue

BACKGROUND Two important signal processing applications in electrophysiology are activation mapping and characterization of the tissue substrate from which electrograms are recorded. We hypothesize that a novel signal-processing method that uses deconvolution is more accurate than amplitude, derivative, and manual activation time estimates. We further hypothesize that deconvolution quantifies changes in morphology that detect electrograms recorded from regions of myocardial infarction. METHODS AND RESULTS To determine the accuracy of activation time estimation, 600 unipolar electrograms were calculated with a detailed computer model using various degrees of coupling heterogeneity to model infarction. Local activation time was defined as the time of peak inward sodium current in the modeled myocyte closest to the electrode. Deconvolution, minimum derivative, and maximum amplitude were calculated. Two experienced electrophysiologists blinded to the computer-determined activation times marked their estimates of activation time. F tests compared the variance of activation time estimation for each method. To evaluate the performance of deconvolution to detect infarction, 380 unipolar electrograms were recorded from 10 dogs with infarcts resulting from ligation of the left anterior descending coronary artery. The amplitude, duration, number of inflections, peak frequency, bandwidth, minimum derivative, and deconvolution were calculated. Metrics were compared by Mann-Whitney rank-sum tests, and receiver operating curves were plotted. CONCLUSIONS Deconvolution estimated local activation time more accurately than the other metrics (P < .0001). Furthermore, the algorithm quantified changes in morphology (P < .0001) with superior performance, detecting electrograms recorded from regions of myocardial infarction. Thus, deconvolution, which incorporates a priori knowledge of electrogram morphology, shows promise to improve present clinical metrics.

Topological representations of thermodynamic systems—I. Basic concepts

Abstract This paper describes the development of a generalized topological representation for thermodynamic systems. The elements and topology of the representation provide a conceptual reticulation of the real system into elements drawn from a set of ideal, but physically realizable, lumped-parameter components. The representation is in the form of bond-graph notation. This notation leads to a graphical description of a dynamic system (very much resembling a chemical bond diagram in appearance) that can be manipulated in an algorithmic fashion to produce the system differential equations, a computer simulation algorithm or a topological (circuit) graph of the system. There is no restriction to linearity in the representation. The reticulated structure represents a conceptual separation of the energy storage and dissipative processes within the system and a description of all the energetic interactions of the system. The ideal components used in the model generalize the familiar electric circuit elements—resistors, capacitors, inductors, transformers—but, unlike electrical circuit diagrams, a reticulation into several components does not necessarily imply any physical separation in the actual system. Bond-graph notation is utilized because it was found to be particularly well suited for dealing with systems involving multiple energy domains with identifiable couplings between them. The thermodynamic systems of general interest comprise ionic flows, fluid flows, chemical reactions, heat flows, etc. with coupling and transduction between all energy modes. Specific applications dealt with here are electro-chemical phenomena. Case studies are presented for relaxation oscillations and rectification in electrolytic systems with multiple ionic flows, chemical reaction and ion-exchange membranes, coupled with electrical circuitry.