Online actor critic algorithm to solve the continuous-time infinite horizon optimal control problem

  • Authors:
  • Kyriakos G. Vamvoudakis;Frank L. Lewis

  • Affiliations:
  • Automation and Robotics Research Institute, University of Texas at Arlington, Fort Worth, TX;Automation and Robotics Research Institute, University of Texas at Arlington, Fort Worth, TX

  • Venue:
  • IJCNN'09 Proceedings of the 2009 international joint conference on Neural Networks
  • Year:
  • 2009

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Abstract

In this paper we discuss an online algorithm based on policy iteration for learning the continuous-time (CT) optimal control solution with infinite horizon cost for nonlinear systems with known dynamics. We present an online adaptive algorithm implemented as an actor/critic structure which involves simultaneous continuous-time adaptation of both actor and critic neural networks. We call this 'synchronous' policy iteration. A persistence of excitation condition is shown to guarantee convergence of the critic to the actual optimal value function. Novel tuning algorithms are given for both critic and actor networks, with extra terms in the actor tuning law being required to guarantee closed-loop dynamical stability. The convergence to the optimal controller is proven, and stability of the system is also guaranteed. Simulation exam pies show the effectiveness of the new algorithm.