A Nonlinear Trajectory Tracking Control Strategy for Quadrotor With Suspended Payload Based on Force Sensor.

To meet the realistic demands of autonomous transportation for quadrotor suspended-payload systems, it is necessary to investigate load trajectory tracking control using only onboard sensing. This paper proposes a nonlinear payload trajectory tracking strategy based on the force sensor. The system employs a force sensor to measure the tension on the cable, in conjunction with the position of the quadrotor, to provide a real-time estimate of the payload position. A payload velocity observer is designed to ensure its status is always available. Furthermore, in order to meet the needs of transporting objects of varying weights, the system utilizes data feedback from the force sensor to autonomously adapt to various payload masses. Based on the payload state estimation, a payload trajectory tracking controller that only relies on onboard sensing to achieve outdoor operation is designed. And multiple sets of simulations and real-world outdoor experiments are performed to validate the effectiveness of the controller. Experimental results show that the proposed control strategy achieves satisfied performance for different payloads and different trajectories.