Two-player zero-sum game based neural critic tracking control for UAUV with unknown disturbance via backstepping method

In this work, a new tracking control scheme is developed for underactuated autonomous underwater vehicle(UAUV) with unknown disturbance. First, an error tracking system is constructed using backstepping method, which transforms the tracking control problem into the two-player zero-sum game problem. One player is the optimal controller which is designed to make the UAUV track the desired trajectory. The other player is the unknown disturbance that represent the overall damping effect of the UAUV. Then, the single critic network based online policy iteration algorithm is designed to get the optimal control law and the worst-case disturbance, which can achieve the near-optimal control performance and relax the requirements for initial admissible control conditions. In order to improve the converge velocity of tracking error, the weight update law are designed. Furthermore, a discount coefficient is introduced into the performance index due to the nonlinearity and the complexity of UAUV. In addition, the stability of the UAUV is analyzed based on the Lyapunov stability theory the system is guaranteed to be uniformly ultimately bounded (UUB). Finally, the effectiveness of the proposed method is demonstrated through the real-time simulations on the UAUV model.