On the cost of fast controls for thermoelastic plates

7 pages, no figures. Submitted November 28, 2005. Accepted October 6, 2006. To appear in Asymptotic Analysis.International audienceThis paper proves that any initial condition in the energy space for the system of thermoelastic plates without rotatory inertia on a smooth bounded domain with hinged mechanical boundary conditions and Dirichlet thermal boundary condition can be steered to zero by a square integrable input function, either mechanical or thermal, supported in arbitrarily small sub-domain and time interval [0,T]. As T tends to zero, for initial states with unit energy norm, the norm of this input function grows at most like exp( C_p / T^p ) for any real p > 1 and some C_p > 0. These results are analogous to the optimal ones known for the heat flow and the proof uses the heat control strategy of Lebeau and Robbiano