Path Invariant Controllers for a Quadrotor With a Cable-Suspended Payload Using a Global Parameterization

Payload delivery using unmanned aerial vehicles (UAVs) has attained central importance for smart logistics and transportation systems in the context of the fourth industrial revolution. This work considers the problem of designing a smooth dynamic feedback control law for a point mass payload suspended to a quadrotor and making the load to follow a large class of curves that includes both closed and non-closed curves. Typically, the load path following problem is solved using either a coordinate-free or a local-coordinate-based approach. However, in this article, we adopt an alternative methodology. First, we express the system dynamics in an extended Euclidean space using a global coordinate system. Second, we propose two families of functions that lead to the design of almost-global and local controllers in terms of region of convergence. We cast the load path following the problem in the framework of set stabilization, and as a result, the proposed controllers make the given path an invariant manifold. The resulting controllers guarantee that once the suspended load converges to the path, it stays on the path indefinitely while satisfying other application-specific constraints. Finally, to complement the theoretical results, we provide a successful real-world experimental validation of the proposed controller on a Quanser QDrone UAV platform with a cable-suspended payload.