We consider optimal control problems with constraints at intermediate points of the trajectory. A natural technique (propagation of phase and control variables) is applied to reduce these problems to a standard optimal control problem of Pontryagin type with equality and inequality constraints at the trajectory endpoints. In this way we derive necessary optimality conditions that generalize the Pontryagin classical maximum principle. The same technique is applied to so-called variable structure problems and to some hybrid problems. The new optimality conditions are compared with the results of other authors and five examples illustrating their application are presented.
Statement of the ProblemOn the interval [t 0 , t ν ] consider the optimal control problem Problem A :where t 0 , t 1 , . . . , t ν are not fixed, x ∈ R n , u ∈ R r , the function x(·) is absolutely continuous, the function u(·) is measurable bounded.Thus, Problem A contains equality and inequality constraints that depend on the values of the phase variable not only at the endpoints of [t 0 , t ν ], but also at the intermediate points t 1 , t 2 , . . . , t ν−1 . If ν = 1, i.e, there are no intermediate points, Problem A is the well-known classical problem of Pontryagin type. In our formulation this problem has been considered in [3,4,6,22]. Particular cases of the problem, without endpoint inequalities and with the endpoint equalities specified separately for the left and right endpoints, have been considered in [1,5] and in many other books and articles.The objective of the present study is to generalize the Pontryagin maximum principle to this class of problems. We will show that Problem A can be reduced to a standard optimal control problem without intermediate constraints.Let the following assumptions hold.(A1) the function f is defined and continuous on the open set Q ⊂ R n+r+1 , the partial derivatives f t , f x , exist on this set and are jointly continuous in all the arguments;