Trajectory tracking control for quadrotor slung-load system: A fuzzy pre-compensation active disturbance rejection control approach

The quadrotor slung-load system exhibits nonlinearity, under-actuation, and strong coupling, making its trajectory tracking prone to degradation under external disturbances and internal parameter uncertainties, thereby reducing tracking accuracy and operational safety. To improve the robustness and trajectory tracking precision of this system, this paper proposes an interval type-2 fuzzy pre-compensation active disturbance rejection control (IT2FP-ADRC) method. First, noting that the linear extended state observer (LESO) suffers from phase lag, which degrades the accuracy of total disturbance estimation, we design a proportional–derivative–acceleration LESO (PDALESO). By introducing phase compensation, the PDALESO captures time-varying total disturbances more timely and accurately, effectively mitigating the adverse effects of phase lag in the LESO. Second, based on the PDALESO, A robust IT2FP-ADRC controller is developed, comprising an interval type-2 fuzzy pre-compensation module, a bandwidth compensation module, and a proportional–derivative linear state-error feedback module. The fuzzy pre-compensation controller takes the quadrotor’s position error and velocity error as inputs, performs fuzzy inference, and outputs a signal to the bandwidth compensator. The bandwidth compensator, using both the fuzzy output and the instantaneous frequency of the desired trajectory signal, flexibly adjusts the bandwidth of the state error feedback controller via fuzzy rules, thereby enhancing control precision. This architecture not only effectively addresses the system’s nonlinearities and uncertainties but also improves its dynamic response and disturbance rejection capability. Experimental results show that the PDALESO suppresses phase lag and significantly enhances the accuracy of total disturbance estimation. In trajectory tracking simulations comparing five control schemes, the proposed IT2FP-ADRC method is validated to substantially improve the trajectory tracking precision and robustness of the quadrotor slung-load system.