Efficient Optimization-based Cable Force Allocation for Geometric Control of a Multirotor Team Transporting a Payload

We consider transporting a heavy payload that is attached to multiplemultirotors. The current state-of-the-art controllers either do not avoidinter-robot collision at all, leading to crashes when tasked with carryingpayloads that are small in size compared to the cable lengths, or usecomputational demanding nonlinear optimization. We propose an efficientoptimization-based cable force allocation for a geometric payload transportcontroller to effectively avoid such collisions, while retaining the stabilityproperties of the geometric controller. Our approach introduces a cascade ofcarefully designed quadratic programs that can be solved efficiently on highlyconstrained embedded flight controllers. We show that our approach exceeds the state-of-the-art controllers in termsof scalability by at least an order of magnitude for up to 10 robots. Wedemonstrate our method on challenging scenarios with up to three smallmultirotors with various payloads and cable lengths, where our controller runsin realtime directly on a microcontroller on the robots.