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

TL;DR

This paper presents an efficient optimization-based method for cable force allocation in multirotor teams transporting payloads, improving collision avoidance and scalability while maintaining stability, and enabling real-time onboard implementation.

Contribution

It introduces a cascade of quadratic programs for cable force allocation that enhances collision avoidance and scalability in multirotor payload transport.

Findings

Outperforms state-of-the-art controllers by at least an order of magnitude in scalability.

Operates in real-time on microcontrollers during complex payload transport scenarios.

Successfully demonstrates collision-free transport with up to 10 robots.

Abstract

We consider transporting a heavy payload that is attached to multiple multirotors. The current state-of-the-art controllers either do not avoid inter-robot collision at all, leading to crashes when tasked with carrying payloads that are small in size compared to the cable lengths, or use computational demanding nonlinear optimization. We propose an efficient optimization-based cable force allocation for a geometric payload transport controller to effectively avoid such collisions, while retaining the stability properties of the geometric controller. Our approach introduces a cascade of carefully designed quadratic programs that can be solved efficiently on highly constrained embedded flight controllers. We show that our approach exceeds the state-of-the-art controllers in terms of scalability by at least an order of magnitude for up to 10 robots. We demonstrate our method on challenging scenarios with up to three small multirotors with various payloads and cable lengths, where our controller runs in realtime directly on a microcontroller on the robots.