Control method improves wrench feasibility for tiltrotor drones
CBF-Based Control Allocation for Omnidirectional Tiltrotor Aerial Robots
Robotics
Summary
Flying robots that tilt their rotors can move and twist in many directions, but changing rotor angles quickly is hard. The authors created a control method that keeps the robot’s force and torque commands possible even when the rotor angles lag behind. They tested their method in simulations and found it kept the drone on track better than existing methods, especially during tricky maneuvers and disturbances. This means the drone can follow complex paths more reliably without losing balance.
What this means in practice
- •For drone control engineers: Maintain feasible force and torque commands during flight despite slow rotor angle changes for better drone maneuvering.
- •For robotics simulation developers: Implement robust wrench allocation techniques to improve aerial robot control accuracy in complex simulated environments.
Authors
Seobeom Lee, Hyondong Oh
Abstract
Actively tilting aerial robots can generate six-dimensional wrenches, but slow servo response can make a desired wrench infeasible during reconfiguration. This paper develops a control barrier function (CBF) allocator that preserves wrench feasibility under bounded servo-configuration mismatch. An exact equivalent-wrench identity connects the thrust required at nominal and actual configurations. For a nonsingular six-channel allocation map, inverse allocation reduces robust wrench containment to twelve thrust margins tightened by an ellipsoidal reserve. Their complete derivatives yield a six-variable servo-rate quadratic program, followed by differential thrust allocation for tracking. A conditional forward-invariance result establishes actual-configuration feasibility under reserve coverage, feasible initialization, and admissible CBF inputs. A complementary MuJoCo study evaluates a measured-angle implementation against geometric, augmented differential, and normalized differential allocation in circular and cartwheel maneuvers, with and without disturbances. The proposed implementation achieves lower position error in all four recorded scenarios, with an attitude tradeoff in circular tracking. During the disturbed cartwheel, the desired wrench is feasible at all 1751 stored samples of continuous rotation; baseline violation rates range from 60.8% to 100%. These comparisons evaluate sampled feasibility; validation of the nominal-trajectory certificate requires nominal-state and reserve-coverage records.