Proceedings of the Thirty-Fourth Southeastern Symposium on System Theory (Cat. No.02EX540)

Epicardial signals are time-varying electric potentials on the outer surface of the heart that originate from a signal inside the heart to trigger the heartbeat. Diagnosis of epicardial signals by medical personnel reveals the health of the heart. Modeling of these signals is important in the inverse problem of electrocardiography. In this paper, we present an inverse technique for computing epicardial signals. We present a finite difference method using Laplace's equation for computing the resistance of an arbitrarily shaped conductor. We demonstrate how this method is useful in modeling the currents inside the body due to static electric fields. By applying this method to a model of the human body, we can develop a network of resistors from the heart to various points on the body surface. From actual electrocardiogram (ECG) measurements at the body surface, we can use the derived network to compute source potentials.

A documentation framework is proposed to assist quality assurance teams in the analysis of complex computer network designs. The framework includes three elements: (1) a requirements definition, (2) a design depiction, and (3) the identification of potentially problematical interfaces. Requirements definition begins with nominal statements describing general design requirements; these statements undergo a process of qualification and quantification, increasing their effectiveness in conveying the purpose of the design. Design depiction presents the system at a high level of abstraction that can be decomposed into functional layers and isolated components. Interface identification allows problematic interfaces to be discovered through intra-component and inter-component analyses. The use of a consistent framework should improve the quality of the design review process.

Certain properties of electronic speed control of three-phase AC motors are described, including some properties that can be modified by the user in the field. Emphasis is placed on the closed-loop operation. Test results for one system are obtained. Using a standard control algorithm from the linear control theory, a method of reducing steady-state speed error is demonstrated. No case of instability is found using various starting speeds, final speeds, and controller parameters for test results. Simulation results are obtained for the closed-loop operation using a controller model previously obtained for open-loop operation of this type system. The model contains multiple nonlinearities. No case of instability is found for various starting speeds, final speeds, controller parameters, and motor parameters for the simulation.

Engineering laboratory equipment at UTC has been made available for users via the World Wide Web. Users can conduct systems lab experiments from remote sites, anytime day-or-night, any day of the week. This paper describes the development of these systems, the current situation and future plans.

Electronic scanning of the beam with phased arrays is faster compared to rotating antennas, and with the phased arrays kept stationery, the beam could be shifted in a manner as desired by the system by controlling the phases. By and large, delay lines are used for producing the necessary phase shifts for the array elements. The use of digital delay lines improve further the rate of scanning and avoids the installation of bulky acoustic delay lines whose performance characteristics are affected by the environment in which it is operated. The recently reported digital delay line has simplicity in controlling the delay lengths from a single analog source. This project employs that digital delay line for scanning the beam in linear directions and also for scanning a sector like raster scanning. The implementations and performance characteristics are reported.

This paper describes a passive coherent location (PCL) radar system developed by Dynetics, Inc. This system uses commercial FM broadcast signals for the radar waveform. This paper presents a technical description of the system and performance data.

An APM classifier is considered for solving the time series classification task. Design, implementation and performance results are discussed. Two main components of the APM are the predictor and credit assignment modules. A system of predictive sigmoid neural networks trained offline is the key part of the predictor module. The credit assignment module is based upon an original credit update equation. No a priori statistical assumptions are required, and the neural predictors do not have to reach optimal training performance criterion to give good classification results. Although additional testing of the classifier is necessary to obtain final conclusions concerning its performance, the results obtained in this paper indicate that the APM classifier has the potential to solve certain classification problems in real time with a limited amount of training data.

The method of strain energy mode shapes allows the determination of changes in structural integrity from changes in the vibrational response of a structure. The modified method presented does not require knowledge of the undamaged state of the structure. Genetic algorithms (GA) are applied to produce a sufficiently optimized amplitude characteristic of a filter used to extract damage information from strain energy mode shapes. Finite element modeling has been used to produce a training data set with the known location of damages. The amplitude characteristic of the filter has been encoded as a genetic string where the pass coefficient for each harmonic of its discrete Fourier transform representation is a number between zero and one in 8-bit Gray code. The genetic optimization has been performed based on the minimization of the signal-to-distortion ratio. The amplitude characteristic of the filter was not limited to any specific configuration, i.e. either low-or high-pass or specific cut-off frequencies. The results obtained from the GA confirmed the theoretical predictions and allowed improvement in the method's sensitivity to damages of lower magnitude.

We present a time-varying sliding mode control (TVSMC) technique for reusable launch vehicle (RLV) attitude control in ascent and entry flight phases. In ascent flight the guidance commands Euler roll, pitch and yaw angles, and in entry flight it commands the aerodynamic angles of bank, attack and sideslip. The controller employs a body rate inner loop and the attitude outer loop, which are separated in time-scale by the singular perturbation principle. The novelty of the TVSMC is that both the sliding surface and the boundary layer dynamics can be varied in real time using the PD-eigenvalue assignment technique. This salient feature is used to cope with control command saturation and integrator windup in the presence of severe disturbance or control effector failure, which enhances the robustness and fault tolerance of the controller.

In this paper we present a spatial power combining architecture consisting of several interacting printed antenna arrays placed at dielectric interfaces in multilayered waveguide. Previously used narrowband resonant patch and slot antennas are replaced by tapered meander slot antennas and their modifications, in order to increase the frequency bandwidth and efficiency of the system and provide operation in multiple band regimes. The full-wave analysis of the interacting antenna modules is based on the integral equation formulation for induced electric and magnetic surface current density discretized via the method of moments. In this formulation, magnetic potential dyadic Green's functions are obtained for a multilayered rectangular waveguide. Numerical results for meander line configurations show significant advantages in scattering characteristics in comparison to traditionally used rectangular slot antennas.