BOUNDARY EXACT CONTROLLABILITY OF INTERFACE PROBLEMS WITH SINGULARITIES .2. ADDITION OF INTERNAL CONTROLS

We prove the exact controllability by boundary action of hyperbolic in terface problems with singularities. The two proposed methods consist of acting by a classical boundary control whose support does not conta in a neighborhood of the singular points and adding internal controls located near these singular points. (See [M.-T. Niane and O. Seck, C. R. Acad. Sci. Paris Ser. I, 318 (1994), pp. 945-948; A. Heibig and M. Moussaoui, Disc. Cent. Dynam. Syst., 2 (1996), pp. 367-386; M.-T. Nian e and O. Seek, C. R. Acad. Sci. Paris Ser. I, 316 (1993), pp. 695-700] , where such a method was introduced.).