Institute for Systems Research

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Subject: search.filters.subject.controllability

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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.
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    A Discrete Event Systems Approach for Protocol Conversion
    (1997) Kumar, Ratnesh; Nelvagal, S.; Marcus, Steven I.; ISR
    A Protocol mismatch occurs when heterogeneous networks try to communicate with each other. Such mismatches are inevitable due to the proliferation of a multitude of networking architectures, hardware, and software on one hand, and the need for global connectivity on the other hand. In order to circumvent this problem the solution of protocol conversion has been proposed. In this paper we present a systematic approach to protocol conversion using the theory of supervisory control of discrete event systems, which was partially first addressed by Inan. We study the problem of designing a converter for a given mismatched pair of protocols, using their specifications, and the specifications for the channel and the user services. We introduce the notion of converter languages and use it to obtain a necessary and sufficient condition for the existence of protocol converter and present an effective algorithm for computing it whenever it exists.
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    Design of Protocol Converters: A Discrete Event Systems Approach
    (1995) Kumar, Ratnesh; Nelvagal, S.; Marcus, Steven I.; ISR
    A protocol mismatch occurs when heterogeneous networks try to communicate with each other. Such mismatches are inevitable due to the proliferation of a multitude of networking architectures, hardware and software on one hand, and the need for global connectivity on the other hand. Global standardization of protocols will avoid such problems, but it may take years to be agreed upon, leaving communication problems for the present. So the alternative solution of protocol conversion has been proposed. In this paper we present a systematic approach to protocol conversion using the recent theory of supervisory control of discrete event systems. We study the problem of designing a converter for a given mismatched pair of protocols, using their specifications and the specifications for the channel and the user services. We introduce the notion of converter languages, use it obtain a necessary and sufficient condition for the existence of protocol converter and present an effective algorithm for computing it whenever it exists.
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    Extension Based Limited Lookahead Supervision of Discrete Event Systems
    (1995) Kumar, Ratnesh; Cheung, Hok M.; Marcus, Steven I.; ISR
    Supervisory control of discrete event systems using limited lookahead has been studied by Chung-Lafortune-Lin, where control is computed by truncating the plant behavior up to the limited lookahead window. We present a different approach in which the control is computed by extending the plant behavior by arbitrary traces beyond the limited lookahead window. The proposed supervisor avoids the notion of pending traces. Consequently the need for considering either a conservative or an optimistic attitude regarding pending traces (as in the work of Chung- Lafortune-Lin) does not arise. It was shown that an optimistic attitude may result in violation of the desired specifications. We demonstrate here that a conservative attitude may result in a restrictive control policy by showing that in some cases the proposed supervisor is less restrictive than the conservative attitude-based supervisor. Moreover, the proposed approach uses the notion of relative closure to construct the supervisor so that it is non-blocking even when the desired behavior is not relative closed (Chung-Lafortune-Lin assume relative closure). Finally, the proposed supervisor possesses all the desirable properties that a conservative attitude based supervisor of Chung-Lafortune-Lin possesses. We illustrate our approach by applying it to concurrency control in database management systems.
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    Linear Feedback Stabilization of Nonlinear Systems with an Uncontrollable Critical Mode
    (1991) Fu, Jyun-Horng; Abed, Eyad H.; ISR
    Linear feedback stabilization of nonlinear systems is studied for systems whose linearization at an equilibrium point possesses a simple critical mode that is uncontrollable. The results complement previous work on the synthesis of nonlinear stabilizing control laws. The present work addresses continuous- time systems for which the linearization has either a simple zero eigenvalue or a pair of simple pure imaginary eigenvalues. Both the stability analysis and stabilizing control design employ results on stability of bifurcations of parametrized systems