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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    Effects of a Temperature Distribution on a Dental Crown System/Analysis, Design and Control of a Hovercraft Model
    (2007-08-21) Snider, Katherine
    Dentral 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.
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    Control and Stabilization of a Class of Nonlinear Systems with Symmetry
    (1998) Manikonda, Vikram; Krishnaprasad, P.S.; ISR; CDCSS
    The focus of this dissertation is to study issues related to controllability and stabilization of a class of underactuated mechanical systems with symmetry. In particular we look at systems whose configuration can be identified with a Lie group and the reduced equations are of the Lie-Poisson type. Examples of such systems include hovercraft, spacecraft and autonomous underwater vehicles. We present sufficient conditions for the controllability of affine nonlinear control systems where the drift vector field is a Lie-Poisson reduced Hamiltonian vector field. In this setting we show that depending on the existence of a radially unbounded Lyapunov type function, the drift vector field of the reduced system is weakly positively Poisson stable. The weak positive Poisson stability along with the Lie algebra rank condition is used to show controllability. These controllability results are then extended to the unreduced dynamics. Sufficient conditions for controllability are presented in both cases where the symmetry group is compact and noncompact. We also present a constructive approach to design feedback laws to stabilize relative equilibria of these systems. The approach is based on the observation that, under certain hypotheses the fixed points of the Lie-Poisson dynamics belong to an immersed equilibrium submanifold. The existence of such equilibrium manifolds, along with the center manifold theory is used to design stabilizing feedback laws.
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    Control Problems of Hydrodynamic Type
    (1998) Krishnaprasad, Perinkulam S.; Manikonda, Vikram; ISR; CDCSS
    It 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)

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    Controllability of Lie-Poisson Reduced Dynamics
    (1997) Manikonda, Vikram; Krishnaprasad, Perinkulam S.; ISR
    In this paper we present sufficient conditions for controllability of Lie-Poisson reduced dynamics of a class of mechanical systems with symmetry. We prove conditions (boundedness of coadjoint orbits and existence of a radially unbounded Lyapunov function) under which the drift vector field (of the reduced system) is weakly positively Poisson stable (WPPS). The WPPS nature of the drift vector field along with the Lie algebra rank condition is used to show controllability of the reduced system. We discuss the dynamics, Lie-Poisson reduction, and controllability of hovercraft, spacecraft and underwater vehicles, all treated as rigid bodies.