Coordinated disturbance observer-based tracking control for unmanned autonomous helicopter under asymmetric time-varying state constraints

This paper investigates the problem on tracking control for a medium-scale unmanned autonomous helicopter (UAH) under external disturbances and full state constraints. First, the nonlinear UAH model is divided into position and attitude subsystems, both of which incorporate the disturbance. Second, for each subsystem, a coordinated disturbance observer (CDO) is developed to accurately estimate the disturbance for compensation. Third, an improved log-type barrier Lyapunov function (LBLF) approach is employed to address the constraint issues on position, velocity, and attitude angle, while a new type of integral-type barrier Lyapunov function (IBLF) is offered to tackle the constraint on attitude angular rate. Fourth, by integrating disturbance estimation and tracking errors, two tracking controllers are presented for the position and attitude loops, resulting in the overall closed-loop system. Then, by utilizing the Lyapunov stability theory, a sufficient condition is established to ensure the uniform boundedness of all error signals. Finally, simulation results are presented to validate the effectiveness and advantage of our proposed control method.