Convergence Analysis of Policy Iteration

Abstract: Adaptive optimal control of nonlinear dynamic systems with deterministic and known dynamics under a known undiscounted infinite-horizon cost function is investigated. Policy iteration scheme initiated using a stabilizing initial control is analyzed in solving the problem. The convergence of the iterations and the optimality of the limit functions, which follows from the established uniqueness of the solution to the Bellman equation, are the main results of this study. Furthermore, a theoretical comparison between the speed of convergence of policy iteration versus value iteration is presented. Finally, the convergence results are extended to the case of multi-step look-ahead policy iteration.