Differential Flatness of Lifting-Wing Quadcopters Subject to Drag and Lift for Accurate Tracking

TL;DR

This paper develops a differential flatness-based control law for lifting-wing quadcopters, enabling precise agile trajectory tracking by incorporating flatness-derived feedforward and feedback to handle disturbances.

Contribution

It introduces a unified control approach using differential flatness for lifting-wing quadcopters with various angles, enhancing tracking accuracy for agile maneuvers.

Findings

Achieves precise trajectory tracking in outdoor tests.

Incorporates jerk as angular velocity for improved bandwidth.

Effectively handles disturbances and model mismatch.

Abstract

In this paper, we propose an effective unified control law for accurately tracking agile trajectories for lifting-wing quadcopters with different installation angles, which have the capability of vertical takeoff and landing (VTOL) as well as high-speed cruise flight. First, we derive a differential flatness transform for the lifting-wing dynamics with a nonlinear model under coordinated turn condition. To increase the tracking performance on agile trajectories, the proposed controller incorporates the state and input variables calculated from differential flatness as feedforward. In particular, the jerk, the 3-order derivative of the trajectory, is converted into angular velocity as a feedforward item, which significantly improves the system bandwidth. At the same time, feedback and feedforward outputs are combined to deal with external disturbances and model mismatch. The control algorithm has been thoroughly evaluated in the outdoor flight tests, which show that it can achieve accurate trajectory tracking.