Reinforcement Learning Solution with Costate Approximation for a Flexible Wing Aircraft

An online adaptive learning approach based on costate function approximation is developed to solve an optimal control problem in real time. The proposed approach tackles the main concerns associated with the classical Dual Heuristic Dynamic Programming techniques in uncertain dynamical environments. It employs a policy iteration paradigm along with adaptive critics to implement the adaptive learning solution. The resultant framework does not need or require prior knowledge of the system dynamics, which makes it suitable for systems with high modeling uncertainties. As a proof of concept, the suggested structure is applied for the auto-pilot control of a flexible wing aircraft with unknown dynamics which are continuously varying at each trim speed condition. Numerical simulations showed that the adaptive control technique was able to learn the system's dynamics and regulate its states as desired in a relatively short time.