Now showing items 1-20 of 161

    • Group structures in a class of control systems 

      Lewis, Andrew D. (1992)
      We investigate two classes of control systems, one of Brockett and one of Murray and Sastry. We are able to show that these two systems may be formulated in the language of principle fibre bundles. Controllability of ...
    • Lagrangian submanifolds and an application to the reduced Schrödinger equation in central force problems 

      Lewis, Andrew D. (D. Reidel, 1992)
      In this Letter, a Lagrangian foliation of the zero energy level is constructed for a family of planar central force problems. The dynamics on the leaves are explicitly computed and these dynamics are given a simple ...
    • Variational principles for constrained systems: theory and experiment 

      Lewis, Andrew D.; Murray, Richard M. (1994)
      In this paper we present two methods, the nonholonomic method and the vakonomic method, for deriving equations of motion for a mechanical system with constraints. The resulting equations are compared. Results are also ...
    • Nonholonomic mechanics and locomotion: the snakeboard example 

      Lewis, Andrew D.; Ostrowski, James P.; Burdick, Joel W.; Murray, Richard M. (IEEE, 1994)
      Analysis and simulations are performed for a simplified model of a commercially available variant on the skateboard, known as the Snakeboard.1 Although the model exhibits basic gait patterns seen in a large number of ...
    • Aspects of Geometric Mechanics and Control of Mechanical Systems 

      Lewis, Andrew D. (1995)
      Many interesting control systems are mechanical control systems. In spite of this, there has not been much effort to develop methods which use the special structure of mechanical systems to obtain analysis tools which ...
    • The geometry of the Gibbs-Appell equations and Gauss's Principle of Least Constraint 

      Lewis, Andrew D. (1995)
      We present a generalisation of the Gibbs-Appell equations which is valid for general Lagrangians. The general form of the Gibbs-Appell equations is shown to be valid in the case when constraints and external forces ...
    • Configuration controllability of simple mechanical control systems 

      Lewis, Andrew D.; Murray, Richard M. (Society for Industrial and Applied Mathematics, 1995)
      In this paper we present a definition of "configuration controllability" for mechanical systems whose Lagrangian is kinetic energy with respect to a Riemannian metric minus potential energy. A computable test for this ...
    • Affine connections and distributions 

      Lewis, Andrew D. (1996)
      We investigate various aspects of the interplay of an affine connection with a distribution. When the affine connection restricts to the distribution, we discuss torsion, curvature, and holonomy of the affine connection. ...
    • Energy-preserving affine connections 

      Lewis, Andrew D. (1997)
      A Riemannian affine connection on a Riemannian manifold has the property that is preserves the ``kinetic energy'' associated with the metric. However, there are other affine connections which have this property, and ...
    • Decompositions of control systems on manifolds with an affine connection 

      Lewis, Andrew D.; Murray, Richard M. (North-Holland, 1997)
      In this letter we present a decomposition for control systems whose drift vector field is the geodesic spray associated with an affine connection. With the geometric insight gained with this decomposition, we are able to ...
    • Lifting distributions to tangent and jet bundles 

      Lewis, Andrew D. (1998)
      We provide two natural ways to lift a distribution from a manifold to its tangent bundle, and show that they agree if and only if the original distribution is integrable. The case when the manifold is the total space ...
    • Towards F=ma in a general setting for Lagrangian mechanics 

      Lewis, Andrew D. (1998)
      By using a suitably general definition of a force, one may geometrically cast the Euler-Lagrange equations in a ``force balance'' form. The key ingredient in such a construction is the Euler-Lagrange 2-force which is a ...
    • Affine connection control systems 

      Lewis, Andrew D. (1999)
      The affine connection formalism provides a useful framework for the investigation of a large class of mechanical systems. Mechanical systems with kinetic energy Lagrangians and possibly with nonholonomic constraints are ...
    • The geometry of the maximum principle for affine connection control systems 

      Lewis, Andrew D. (2000)
      The maximum principle of Pontryagin is applied to systems where the drift vector field is the geodesic spray corresponding to an affine connection. The result is a second-order differential equation whose right-hand side ...
    • Optimal control for a simplified hovercraft model 

      Coombs, A. Theo; Lewis, Andrew D. (2000)
      Time-optimal and force-optimal extremals are investigated for a planar rigid body with a single variable direction thruster. A complete and explicit characterisation of the singular extremals is possible for this problem.
    • Controllability and motion algorithms for underactuated Lagrangian systems on Lie groups 

      Bullo, Francesco; Leonard, Naomi E.; Lewis, Andrew D. (IEEE, 2000)
      In this paper, we provide controllability tests and motion control algorithms for underactuated mechanical control systems on Lie groups with Lagrangian equal to kinetic energy. Examples include satellite and underwater ...
    • Simple mechanical control systems with constraints 

      Lewis, Andrew D. (IEEE, 2000)
      We apply some recently developed control theoretic techniques to the analysis of a class of mechanical systems with constraints. Certain simple aspects of the theory of affine connections play an important part in our ...
    • On the homogeneity of the affine connection model for mechanical control systems 

      Bullo, Francesco; Lewis, Andrew D. (IEEE, 2000)
      This work presents a review of a number of control results for mechanical systems. The key technical results derive mainly from the homogeneity properties of affine connection models for a large class of mechanical systems. ...
    • Controllable kinematic reductions for mechanical systems: concepts, computational tools, and examples 

      Bullo, Francesco; Lewis, Andrew D.; Lynch, Kevin M. (2001)
      This paper introduces the novel notion of kinematic reductions for mechanical systems and studies their controllability properties. We focus on the class of simple mechanical control systems with constraints and model ...
    • Geometric local controllability: second-order conditions 

      Hirschorn, Ron M.; Lewis, Andrew D. (2002)
      In a geometric point of view, a nonlinear control system, affine in the controls, is thought of as an affine subbundle of the tangent bundle of the state space. In deriving conditions for local controllability from ...