Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Modeling and Optimization for Epitaxial Growth: Transport and Growth Studies(1999) Newman, Andrew J.; Krishnaprasad, Perinkulam S.; Krishnaprasad, Perinkulam S.; ISR; CDCSSThis report details the objectives, methodologies, and results for Phase II ofthe project, "Modeling and Optimization for Epitaxial Growth"(see~cite{NKPB98} for Phase I report). This project is a joint effort betweenthe Institute for Systems Research (ISR) and Northrop Grumman'sElectronic Sensors and Systems Sector (ESSS), Baltimore, MD.The overallobjective is to improve manufacturing effectiveness for epitaxial growth ofsilicon and silicon-germanium (Si-Ge) thin films on a silicon wafer. Growthtakes place in the ASM Epsilon-1 chemical vapor deposition (CVD) reactor, aproduction tool currently in use at ESSS. Phase II project results includedevelopment of a new comprehensive process-equipment model capable ofpredicting gas flow, heat transfer, species transport, and chemical mechanismsin the reactor under a variety of process conditions and equipment settings.
Applications of the model include prediction and control of deposition rate andthickness uniformity; studying sensitivity of deposition rate to processsettings such as temperature, pressure, and flow rates; and reducing the use ofconsumables via purge flow optimization. The implications of varioussimulation results are discussed in terms of how they can be used to reducecosts and improve product quality, e.g., thickness uniformity of thin films. We demonstrate that achieving deposition uniformity requires some degree oftemperature non-uniformity to compensate for the effects of other phenomenasuch as reactant depletion, gas heating and gas phase reactions, thermaldiffusion of species, and flow patterns.
Item Analysis of a complex activator-inhibitor equation(1999) Justh, Eric W.; Krishnaprasad, Perinkulam S.; ISR; CDCSSBasic properties of solutions and a Lyapunov functionalare presented for a complex activator-inhibitor equation witha cubic nonlinearity.Potential applications include control of coupled-oscillator arrays(for quasi-optical power combining and phased-array antennas),and control of MEMS actuator arrays (for micro-positioning small items).(This work to appear in Proc. 1999 American Control Conference.)
Item Control Problems of Hydrodynamic Type(1998) Krishnaprasad, Perinkulam S.; Manikonda, Vikram; ISR; CDCSSIt has been known for some time that the classical work of Kirchhoff, Love,and Birkhoff on rigid bodies in incompressible, irrotational flows provideseffective models for treating control problems for underwater vehicles.This has also led to a better appreciation of the dynamics of suchsystems. In this paper, we develop results based on geometric mechanics andcenter manifold theory to solve controllability and stabilization questionsfor a class of under-actuated left invariant mechanical systems on Liegroups that include approximate models of underwater vehicles and surfacevehicles. We also provide numerical evidence to capture the globalproperties of certain interesting feedback laws.(This work appears as an invited paper in the Proc. IFAC Sympo. on NonlinearControl Systems Design (NOLCOS'98), (1998), 1:139-144)
Item Nonlinear Model Reduction for RTCVD(1998) Newman, A.; Krishnaprasad, Perinkulam S.; Krishnaprasad, Perinkulam S.; ISR; CDCSSIn this paper, we examine alternative methods for reducing thedimensionality of nonlinear dynamical system models arising incontrol of rapid thermal chemical vapor deposition (RTCVD) forsemiconductor manufacturing. We focus on model reduction forthe ordinary differential equation model describing heattransfer to, from, and within a semiconductor wafer in theRTCVD chamber. Two model reduction approaches are studied andcompared: the proper orthogonal decomposition and the method of balancing.This leads to a discussion of computational issues in the practicalimplementation of balancing for nonlinear systems.Item Efficient Implementation of Controllers for Large Scale Linear Systems via Wavelet Packet Transforms(1998) Kantor, George A.; Krishnaprasad, Perinkulam S.; ISR; CDCSSIn this paper we present a method of efficiently implementing controllers for linear systems with large numbers of sensors and actuators. It is well known that singular value decomposition can be used to diagonalize any real matrix. Here, we use orthogonal transforms from the wavelet packet to "approximate" SVD of the plant matrix. This yields alternatebases for the input and output vector which allow for feedback control using local information. This fact allows for the efficient computation of a feedback control law in the alternate bases. Since the wavelet packet transforms are also computationally efficient,this method provides a good alternative to direct implementation of a controller matrix for large systems.This paper was presented at the 32nd CISS, March 18-21, 1998.
Item A Model for a Thin Magnetostrictive Actuator(1998) Venkataraman, R.; Krishnaprasad, Perinkulam S.; ISR; CDCSSIn this paper, we propose a model for dynamic magnetostrictive hysteresisin a thin rod actuator. We derive two equations that representmagnetic and mechanical dynamic equilibrium. Our model results from an application of the energy balance principle.It is a dynamic model as it accounts for inertial effects and mechanicaldissipation as the actuator deforms, and also eddy current lossesin the ferromagnetic material. We show rigorously that the model admits a periodic solution thatis asymptotically stable when a periodic forcing function is applied.(Proc. Conf. Information Sci. and Systems, Princeton, March 1998)Item A Lyapunov Functional for the Cubic Nonlinearity Activator-Inhibitor Model Equation(1998) Justh, Eric W.; Krishnaprasad, Perinkulam S.; ISR; CDCSSThe cubic nonlinearity activator-inhibitor model equation is a simpleexample of a pattern-forming system for which strong mathematical resultscan be obtained. Basic properties of solutions and the derivation ofa Lyapunov functional for the cubic nonlinearity model are presented.Potential applications include control of large MEMS actuator arrays.(In Proc. IEEE Conf. Decision and Control, December 16-18, 1998)Item The Hybrid Motor Prototype: Design Details and Demonstration Results(1998) Venkataraman, R.; Dayawansa, Wijesuriya P.; Krishnaprasad, Perinkulam S.; ISR; CDCSSA novel hybrid rotary motor incorporating piezoelectric and magnetostrictive actuators has been designed and demonstrated. The novelty of this motor was the creation of an electrical resonant circuit, whereby reactive power requirement on the power source is reduced. It was envisioned that the motor would be suitable for low output speed, high torque applications because of its design. This report presents the constructional details of this motor and the results of the demonstration.Item Characterization of an ETREMA MP 50/6 Magnetostrictive Actuator(1998) Venkataraman, R.; Rameau, J.; Krishnaprasad, Perinkulam S.; ISR; CDCSSThis report presents the Displacement (Strain)-Current characteristic of an ETREMA MP 50/6 magnetostrictive actuator. This actuator is made of TERFENOL-D and displays giant magnetostriction. The displacement-current characteristic shows significant hysteresis behavior that depends on the rate at which the input is applied. Another important property of ferromagnetic hysteresis - the wiping out property, was also observed in the experiments.Item Modeling and Model Reduction for Control and Optimization of Epitaxial Growth in a Commercial Rapid Thermal Chemical Vapor Deposition Reactor(1998) Newman, Andrew J.; Krishnaprasad, Perinkulam S.; Ponczak, Sam; Brabant, Paul; Krishnaprasad, Perinkulam S.; ISRIn December 1996, a project was initiated at the Institute for Systems Research (ISR), under an agreement between Northrop GrummanElectronic Sensors and Systems Division (ESSD) and the ISR, to investigatethe epitaxial growth of silicon-germanium (Si-Ge) heterostructures in a commercial rapid thermal chemical vapor deposition (RTCVD) reactor. This report provides a detailed account of the objectives and results of work done on this project as of September 1997. The report covers two maintopics: modeling and model reduction. Physics-based models are developedfor thermal, fluid, and chemical mechanisms involved in epitaxial growth.Experimental work for model validation and determination of growth parameters is described. Due to the complexity and high computational demands of the models, we investigate the use of model reduction techniques to reduce the model complexity, leading to faster simulation and facilitating the use of standard control and optimization strategies.