Geometric Backstepping Control of Omnidirectional Tiltrotors Incorporating Servo�Rotor Dynamics for Robustness against Sudden Disturbances
Jaewoo Lee, Dongjae Lee, Jinwoo Lee, Hyungyu Lee, Yeonjoon Kim, H. Jin Kim
AI summary
Problem
Existing control strategies for omnidirectional multirotors often ignore or linearize actuator dynamics, causing instability or crashes during aggressive maneuvers and sudden external disturbances.
Approach
The authors develop a geometric backstepping controller that exploits the nonlinear cascade between rigid-body and first-order actuator dynamics, using Lyapunov analysis to guarantee stability and robustness against parametric uncertainty.
Key results
- A geometric backstepping framework explicitly coupling servo and rotor dynamics
- Lyapunov-based proof of exponential stability and ultimate boundedness under parametric uncertainty
- Experimental validation showing superior tracking and disturbance recovery over a baseline controller
- Demonstration that ignoring actuator dynamics causes crashes during aggressive translation and sudden impact recovery
Why it matters
Enables reliable, high-performance operation of omnidirectional multirotors in demanding real-world tasks like aerial manipulation and inspection by preventing control-induced instability.
Abstract
This work presents a geometric backstepping controller for a variable-tilt omnidirectional multirotor that explicitly accounts for both servo and rotor dynamics. Consider- ing actuator dynamics is essential for more effective and reliable operation, particularly during aggressive flight maneuvers or recovery from sudden disturbances. While prior studies have investigated actuator-aware control for conventional and fixed- tilt multirotors, these approaches rely on linear relationships between actuator input and wrench, which cannot capture the nonlinearities induced by variable tilt angles. In this work, we exploit the cascade structure between the rigid-body dynamics of the multirotor and its nonlinear actuator dynamics to design the proposed backstepping controller and establish exponential stability of the overall system. Furthermore, we reveal parametric uncertainty in the actuator model through experiments, and we demonstrate that the proposed controller remains robust against such uncertainty. The controller was compared against a baseline that does not account for actuator dynamics across three experimental scenarios: fast translational tracking, rapid rotational tracking, and recovery from sudden disturbance. The proposed method consistently achieved better tracking performance, and notably, while the baseline diverged and crashed during the fastest translational trajectory tracking and the recovery experiment, the proposed controller main- tained stability and successfully completed the tasks, thereby demonstrating its effectiveness.