452 research outputs found
Bounded-From-Below Solutions of the Hamilton-Jacobi Equation for Optimal Control Problems with Exit Times: Vanishing Lagrangians, Eikonal Equations, and Shape-From-Shading
We study the Hamilton-Jacobi equation for undiscounted exit time control
problems with general nonnegative Lagrangians using the dynamic programming
approach. We prove theorems characterizing the value function as the unique
bounded-from-below viscosity solution of the Hamilton-Jacobi equation which is
null on the target. The result applies to problems with the property that all
trajectories satisfying a certain integral condition must stay in a bounded
set. We allow problems for which the Lagrangian is not uniformly bounded below
by positive constants, in which the hypotheses of the known uniqueness results
for Hamilton-Jacobi equations are not satisfied. We apply our theorems to
eikonal equations from geometric optics, shape-from-shading equations from
image processing, and variants of the Fuller Problem.Comment: 29 pages, 0 figures, accepted for publication in NoDEA Nonlinear
Differential Equations and Applications on July 29, 200
Further Results on Lyapunov Functions for Slowly Time-Varying Systems
We provide general methods for explicitly constructing strict Lyapunov
functions for fully nonlinear slowly time-varying systems. Our results apply to
cases where the given dynamics and corresponding frozen dynamics are not
necessarily exponentially stable. This complements our previous Lyapunov
function constructions for rapidly time-varying dynamics. We also explicitly
construct input-to-state stable Lyapunov functions for slowly time-varying
control systems. We illustrate our findings by constructing explicit Lyapunov
functions for a pendulum model, an example from identification theory, and a
perturbed friction model.Comment: Accepted for publication in Mathematics of Control, Signals, and
Systems (MCSS) on November 20, 200
Further Constructions of Control-Lyapunov Functions and Stabilizing Feedbacks for Systems Satisfying the Jurdjevic-Quinn Conditions
For a broad class of nonlinear systems, we construct smooth control-Lyapunov
functions whose derivatives along the trajectories of the systems can be made
negative definite by smooth control laws that are arbitrarily small in norm. We
assume our systems satisfy appropriate generalizations of the Jurdjevic-Quinn
conditions. We also design state feedbacks of arbitrarily small norm that
render our systems integral-input-to-state stable to actuator errors.Comment: 15 pages, 0 figures, accepted for publication in IEEE Transactions on
Automatic Control in October 200
On the Strong Invariance Property for Non-Lipschitz Dynamics
We provide a new sufficient condition for strong invariance for differential
inclusions, under very general conditions on the dynamics, in terms of a
Hamiltonian inequality. In lieu of the usual Lipschitzness assumption on the
multifunction, we assume a feedback realization condition that can in
particular be satisfied for measurable dynamics that are neither upper nor
lower semicontinuous.Comment: 15 pages, 0 figures. For this revision, the authors added a remark
about an alternative nonconstructive proof of the main resul
Further Results on Strict Lyapunov Functions for Rapidly Time-Varying Nonlinear Systems
We explicitly construct global strict Lyapunov functions for rapidly
time-varying nonlinear control systems. The Lyapunov functions we construct are
expressed in terms of oftentimes more readily available Lyapunov functions for
the limiting dynamics which we assume are uniformly globally asymptotically
stable. This leads to new sufficient conditions for uniform global exponential,
uniform global asymptotic, and input-to-state stability of fast time-varying
dynamics. We also construct strict Lyapunov functions for our systems using a
strictification approach. We illustrate our results using a friction control
example.Comment: 10 pages, 0 figues, revised and accepted for publication as a regular
paper in Automatica in May 2006. To appear in October 2006 issu
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