Now showing items 21-33 of 33

    • 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.
    • 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 ...
    • 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 ...
    • 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 ...
    • 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 ...
    • 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. ...
    • 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 ...
    • 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 ...
    • 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 ...
    • Jacobian linearisation in a geometric setting 

      Lewis, Andrew D.; Tyner, David R. (IEEE, 2003)
      Linearisation is a common technique in control applications, putting useful analysis and design methodologies at the disposal of the control engineer. In this paper, linearisation is studied from a differential ...