Overactuated multirotor control improves delay robustness without Lipschitz constants
Delay-Certified Readiness Barriers for Overactuated Multirotor Allocation Without Lipschitz Constants
Robotics
Summary
Multirotor drones can use many different ways to spin their rotors to move, but some ways make it hard to respond quickly to things like wind gusts. The authors found a way to guarantee drones keep enough control readiness even when there are delays in sending commands, without needing tricky math constants called Lipschitz constants. They do this by checking the worst-case control readiness in a simple way based on the drone’s rotor responses. Their method worked well in simulations with varying delays and was safer than some existing approaches.
What this means in practice
- •For drone control engineers: Maintain stable flight control despite variable delays when allocating rotor speeds in overactuated multirotors.
- •For unmanned aerial vehicle operators: Ensure reliable disturbance rejection for hexarotors operating with uncertain communication and actuation delays.
Authors
Giuseppe Silano
Abstract
Overactuated multirotors can produce the same wrench with many rotor-speed combinations, some of which leave the vehicle unable to change its wrench quickly, e.g., to reject a gust. Readiness barriers keep this ability, the readiness, above a floor, but only in continuous time; with sampled commands and varying speed-controller delays, the available robustness bound covers less than one millisecond. We remove this limit by exploiting the structure of the problem: each rotor responds monotonically and in closed form to its own torque, so the speeds reachable under uncertain switching times lie in a cheaply computed box, and the lowest readiness over that box sits at a corner known in advance. This yields a Lipschitz-free test that a command keeps the readiness above its floor until the next sample, plus a fallback torque that keeps the vehicle on a certified plan. In hexarotor simulations with 2--40~ms delays and $\pm2$~ms jitter, the filter never violated the floor. At $10\pm2$~ms, it matched a delay-compensating predictor within the design envelope and cost 2--30\% more tracking error beyond it, where the predictor alone violated the floor in 2 to 16 of 16 missions.