M. Moussaoui et A. Seeger, APPROXIMATE PONTRYAGIN PRINCIPLE AND PERT URBATION ANALYSIS OF CONVEXOPTIMAL-CONTROL PROBLEMS, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 319(8), 1994, pp. 849-854
We characterize the subdifferential of the optimal-value function of a
convexly perturbed optimal control problem. We do not assume the exis
tence of optimal solutions to the unperturbed problem.