Energy-Efficient Optimal Control of a Hexarotor UAV Based on High-Order Fully Actuated Gust Disturbance Rejection

To address the challenge of simultaneously satisfying attitude stability constraints and achieving multi-motor energy efficiency optimization for a hexarotor UAV under complex low-altitude gust disturbances, this paper proposes a coordinated control method that integrates high-order fully actuated disturbance rejection with energy-efficient allocation. First, a low-altitude composite wind field model incorporating random wind, gusts, and improved Dryden turbulence is established. On this basis, a mapping relationship from wind field parameters to attitude disturbance torque and motor load is constructed to characterize the load imbalance among the six motors induced by gust disturbances. Second, an extended state observer (ESO) is designed at the attitude layer to estimate and compensate for the equivalent disturbances in the angular-acceleration channels. At the actuator layer, a bank of six Z-type extended state observers (ZESOs) is constructed to estimate the lumped disturbance acting on each individual motor channel. Based on the compensated motor dynamics, a coordination protocol is further developed to ensure coordinated reference tracking of the six motors under nonuniform gust loads and actuator constraints. Finally, a quadratic programming-based energy-efficient allocation model is developed with the objective of minimizing the total system loss, and a stability-index-driven switching mechanism between the strong disturbance-rejection mode and the energy-saving mode is designed. The proposed method thereby enables the coordinated optimization of attitude stability and actuator layer energy efficiency under gust disturbances.