6,626 research outputs found
Carleman estimate for an adjoint of a damped beam equation and an application to null controllability
In this article we consider a control problem of a linear Euler-Bernoulli
damped beam equation with potential in dimension one with periodic boundary
conditions. We derive a new Carleman estimate for an adjoint of the equation
under consideration. Then using a well known duality argument we obtain
explicitly the control function which can be used to drive the solution
trajectory of the control problem to zero state
Some Controllability Results for Linearized Compressible Navier-Stokes System
In this article, we study the null controllability of linearized compressible
Navier-Stokes system in one and two dimension. We first study the
one-dimensional compressible Navier-Stokes system for non-barotropic fluid
linearized around a constant steady state. We prove that the linearized system
around , with is
not null controllable by localized interior control or by boundary control. But
the system is null controllable by interior controls acting everywhere in the
velocity and temperature equation for regular initial condition. We also prove
that the the one-dimensional compressible Navier-Stokes system for
non-barotropic fluid linearized around a constant steady state , with is not
null controllable by localized interior control or by boundary control for
small time Next we consider two-dimensional compressible Navier-Stokes
system for barotropic fluid linearized around a constant steady state We prove that this system is also not null controllable by
localized interior control
Local controllability of 1D linear and nonlinear Schr\"odinger equations with bilinear control
We consider a linear Schr\"odinger equation, on a bounded interval, with
bilinear control, that represents a quantum particle in an electric field (the
control). We prove the controllability of this system, in any positive time,
locally around the ground state. Similar results were proved for particular
models (by the first author and with J.M. Coron), in non optimal spaces, in
long time and the proof relied on the Nash-Moser implicit function theorem in
order to deal with an a priori loss of regularity. In this article, the model
is more general, the spaces are optimal, there is no restriction on the time
and the proof relies on the classical inverse mapping theorem. A hidden
regularizing effect is emphasized, showing there is actually no loss of
regularity. Then, the same strategy is applied to nonlinear Schr\"odinger
equations and nonlinear wave equations, showing that the method works for a
wide range of bilinear control systems
Controllability of the 1D Schrodinger equation by the flatness approach
We derive in a straightforward way the exact controllability of the 1-D
Schrodinger equation with a Dirichlet boundary control. We use the so-called
flatness approach, which consists in parameterizing the solution and the
control by the derivatives of a "flat output". This provides an explicit
control input achieving the exact controllability in the energy space. As an
application, we derive an explicit pair of control inputs achieving the exact
steering to zero for a simply-supported beam
Explicit approximate controllability of the Schr\"odinger equation with a polarizability term
We consider a controlled Schr\"odinger equation with a dipolar and a
polarizability term, used when the dipolar approximation is not valid. The
control is the amplitude of the external electric field, it acts non linearly
on the state. We extend in this infinite dimensional framework previous
techniques used by Coron, Grigoriu, Lefter and Turinici for stabilization in
finite dimension. We consider a highly oscillating control and prove the
semi-global weak stabilization of the averaged system using a Lyapunov
function introduced by Nersesyan. Then it is proved that the solutions of the
Schr\"odinger equation and of the averaged equation stay close on every finite
time horizon provided that the control is oscillating enough. Combining these
two results, we get approximate controllability to the ground state for the
polarizability system
The dynamics and control of large flexible space structures, 2. Part A: Shape and orientation control using point actuators
The equations of planar motion for a flexible beam in orbit which includes the effects of gravity gradient torques and control torques from point actuators located along the beam was developed. Two classes of theorems are applied to the linearized form of these equations to establish necessary conditions for controlability for preselected actuator configurations. The feedback gains are selected: (1) based on the decoupling of the original coordinates and to obtain proper damping, and (2) by applying the linear regulator problem to the individual model coordinates separately. The linear control laws obtained using both techniques were evaluated by numerical integration of the nonlinear system equations. Numerical examples considering pitch and various number of modes with different combination of actuator numbers and locations are presented. The independent model control concept used earlier with a discretized model of the thin beam in orbit was reviewed for the case where the number of actuators is less than the number of modes. Results indicate that although the system is controllable it is not stable about the nominal (local vertical) orientation when the control is based on modal decoupling. An alternate control law not based on modal decoupling ensures stability of all the modes
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