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 Optimal Preview Control of Markovian Jump Linear Systems(2008) Kenneth, Running; Nuno, MartinsIn this paper, we investigate the design of controllers, for discrete-time Markovian jump linear systems, that achieve optimal reference tracking in the presence of preview (reference look-ahead). For a quadratic cost and given a reference sequence, we obtain the optimal solution for the full information case. The optimal control policy consists of the additive contribution of two terms: a feedforward term and a feedback term. We show that the feedback term is identical to the standard optimal linear quadratic regulator for Markovian jump linear systems. We provide explicit formulas for computing the feedforward term, including an analysis of convergence.Item A convex parameterization of all stabilizing controllers for non-strongly stabilizable plants, under quadratically invariant sparsity constraints(2008) Sabau, Serban; Martins, Nuno; Rotkowitz, MichaelThis paper addresses the design of controllers, subject to sparsity constraints, for linear and timeinvariant plants. Prior results have shown that a class of stabilizing controllers, satisfying a given sparsity constraint, admits a convex representation of the Youla–type, provided that the sparsity constraints imposed on the controller are quadratically invariant with respect to the plant and that the plant is strongly stabilizable. Another important aspect of the aforementioned results is that the sparsity constraints on the controller can be recast as convex constraints on the Youla parameter, which makes this approach suitable for optimization using norm-based costs. In this paper, we extend these previous results to non-strongly stabilizable plants. Our extension also leads to a Youla-type representation for the class of controllers, under quadratically invariant sparsity constraints. In our extension, the controller class also admits a representation of the Youla–type, where the Youla parameter is subject to only convex constraints.Item Effects of a Temperature Distribution on a Dental Crown System/Analysis, Design and Control of a Hovercraft Model(2007-08-21) Snider, KatherineDentral Crown: A dental crown system is a type of extracoronal restoration, or a restoration that exists around a remaining tooth structure. It is used in situations where there is not enough remaining solid tooth structure after decay or when a tooth has fractured and is missing important structural reinforcements. It typically consists of four layers, including the original tooth core, a layer of cement, a crown layer to provide the structural support, and a veneer layer that gives the look of a real tooth. All of these layers were created and assembled in order to accurately represent a crown system for the project. The goal of this project is to determine the effects of a temperature change on the maximum principle stress for the crown layer of the system. This helps determine how long the crown can be used before it will break. Temperature and stress analyses will be done for four different material combinations in order to see what effect these have on the system as well as what materials are better to use for a crown system. Hovercraft: A hovercraft is a special type of vehicle that moves on a cushion of air. The lifting motion is controlled by a fan or fans so that an air gap can be formed beneath the vehicle. Such separation between the bottom of the hovercraft and the ground provides a motion platform, on which the friction force between the hovercraft and the ground reduces to a very small amount. Since a hovercraft does not have wheels, the forward motion is created through propulsion, which is generated by the use of a fan or set of fans located on the back end of the hovercraft. These propulsion fans send the air backward to produce a thrust force, which moves the hovercraft forward. The goal of this project is to analyze, create, and control a working hovercraft model. Initially, flow analysis will be performed on a hovercraft model created in SolidWorks. After a design has been found that provides the necessary lift force, the model will be constructed using materials provided by the University of Maryland. Once the model is assembled and working, programming will be done in order to control the motion of the hovercraft. This will be done using an NXT control box. The ultimate goal is to have the model follow a specified path by using feedback from light sensors to control the movement.Item An Optical Area-Scattering Based Approach for the Measurement of Surface Roughness Formed During Machining(1993) DeVoe, Don L.; Zhang, G.M.; ISRThe measurement of surface roughness during a machining process is critical for the automatic control of surface quality in a computer-integrated manufacturing (CIM) system. In this work, a method of surface roughness assessment is investigated which is particularly applicable for in-process roughness measurement. The measurement system employs a novel application of light- scattering theory, which has been used in a number of commercially available optical surface roughness measurement techniques.The need for such a measurement system is discussed, and a review of several systems currently available for this purpose is provided. The theory upon which many of these optical system is based is introduced, and the theory is extended for application to the measurement system introduced in this work. The differences and advantages of the developed vision system, compared to other optical systems, are investigated. Particular attention is paid to the area-based nature of the new technique. The performance of a prototype vision system is considered, and the results of a factorial design are interpreted to determine the sensitivity of the system to six environmental and system configuration factors. A calibration curve, which relates the surface roughness of fifty aluminum workpieces to an optical roughness parameter, is developed to provide a method of determining surface roughness directly from optical measurements. A prototype of a second optical system is constructed to attach directly to a CNC milling machine, and the suitability of this system for use in a machining environment is investigated.
There are three stages of this work. In the first stage, a preliminary experimental study is performed to investigate some of the basic attributes of the vision system. While this study is fairly simple, it demonstrates the potential usefulness of the proposed system. In the second stage, a prototype vision system is designed and constructed, and a detailed factorial design is undertaken to develop an empirical model of the system output as a function of six factors related to the system configuration and environmental conditions. Several calibration curves are produced for relating the system output to a range of known surface roughnesses. In the third stage, a prototype system is integrated with a Computer Numerically Controlled (CNC) milling machine to investigate the feasibility of using the system in a true machining environment. The results indicate some of the advantages and limitations of the proposed system.
Item Reconfigurable Control in Discrete Event Dynamic Systems Applied to Manufacturing Systems(1993) Dhingra, Jastej S.; Blankenship, Gilmer L.; ISRProduction management in an automated manufacturing system entails the implementation of the following two decision functions: Operational Planning and Resource Allocation, and Production Control. In this work we present scheduling and production control algorithms for manufacturing systems. We present a general manufacturing system model and formalize the concept of a schedule as a single sequence of operations. Using a general performance measure we formulate the operations scheduling problem as a combinatorial optimization problem. A simulated annealing based optimization algorithm is developed for this job shop scheduling problem. We present a three level hierarchical on-line reconfigurable control scheme. For the "process" level control, we present a reactive operations scheduling scheme. Based on the control specification at the process level, the lower "operation" level parameters are defined. We present operation control algorithms for both continuous and batch mode processing. Using dynamic programming principles, we present a Quasi-Variational Inequality based impulse control algorithm for online control of processing rates for a single batch. Perturbation Analysis, in conjunction with stochastic approximation techniques, is used for continuous mode, online processing rate control. Algorithm extensions to other discrete event systems are also discussed.Item Feedback Control of Bifurcation and Chaos in Dynamical Systems(1993) Abed, Eyad H.; Wang, H.O.; ISRFeedback control of bifurcation and chaos in nonlinear dynamical systems is discussed. The article summarizes some of the recent work in this area, including both theory and applications. Stabilization of period doubling bifurcations and of the associated route to chaos is considered. Open problems in bifurcation control are noted.Item Bifurcation Control of chaotic Dynamical Systems(1992) Wang, H.O.; Abed, Eyad H.; ISRA nonlinear system which exhibits bifurcations, transient chaos, and fully developed chaos is considered, with the goal of illustrating the role of two ideas in the control of chaotic dynamical systems. The first of these ideas is the need for robust control, in the sense that, even with an uncertain dynamic model of the system, the design ensures stabilization without at the same time changing the underlying equilibrium structure of the system. Secondly, the paper shows how focusing on the control of primary bifurcations in the model can result in the taming of chaos. The latter is an example of the 'bifurcation control' approach. When employed along with a dynamic feedback approach to the equilibrium structure preservation issue noted above, this results in a family of robust feedback controllers by which one can achieve various types of 'stability' for the system.