Control by coefficients in the Elrod-Adams model

The purpose of this paper is to study a control by coefficients problem issued from the elastohydrodynamic lubrication. The control variable is the film thickness. The cavitation phenomenon takes place and described by the Elrod-Adams model, suggested in preference to the classical variational inequality due to its ability to describe input and output ow. The idea is to use the penalization in the state equation by approximating the Heaviside graph whith a sequence of monotone and regular functions. We derive a necessary condition for the regularized problem, then we establish estimates of the state and the adjoint state in the one dimensional case. Next we pass to the limit.