TRP-Controller: An Efficient Anti-Saturation Controller for Quadrotors Performing Yaw-low-priority Motions

The flight controller is a basic component for quadrotors. The thrust of each rotor is controlled to realize 3D linear motion and yaw rotation. Limited by the maximum thrust of each rotor, the saturation phenomenon happens when the control inputs are large. This phenomenon is especially obvious in situations where the quadrotor is flying at a high speed while rotating yaw at the same time for sensing purpose. In these situations, yaw rotation can usually be assigned with a lower control priority compared to linear motions to guarantee the tracking accuracy of the flight trajectory. In this paper, an anti-saturation controller is proposed to improve linear motion tracking performance in these yaw-low-priority flights. By deriving from the dynamic model of the quadrotor, sufficient conditions to realize accurate linear motion control without saturation are presented. An efficient thrust mixer is then derived by considering collective thrust, roll, and pitch first and yaw later. Finally, a complete flight controller is established and released as an open-source repository. To evaluate the performance of the proposed controller, experiments were conducted to compare the tracking error with the popular PX4 flight controller. Results show that when the yaw angle is planned to rotate very fast, the average tracking error of linear motion increases by 188.1% with the PX4 controller while only 79.9 % with our controller.