Readiness Barrier Functions: Forward-Invariant Control Authority for Overactuated Multirotor Allocation

2026-08-17

AI Summary

This study addresses command discontinuities and the lack of torque rate authority in over-actuated multirotor control allocation. We propose a framework integrating log-determinant forward-invariant control barrier functions with null-space quadratic programming. This approach models authority constraints as forward-invariant sets, providing closed-form costs for rotor deactivation and robust handling of parametric uncertainties to ensure both control continuity and safety certification. Simulations demonstrate that the closed-form solution achieves machine-level precision. Under authority-saturated conditions, tracking errors are reduced by a factor of 80 compared to greedy methods while strictly maintaining set invariance. Consequently, this method effectively resolves the critical trade-off between operational safety and control smoothness in over-actuated aerial systems.

Abstract

Allocation schemes that greedily maximize a readiness metric over the actuator fiber bundle of an overactuated multirotor produce commands that jump between disconnected optimal strata, demanding actuator rates no motor can deliver; effort-minimizing schemes are continuous but cannot guarantee that wrench-rate authority stays above any certified level. We reconcile the two by treating authority as a forward-invariant quantity: a control barrier function on the log-determinant of the drag-aware actuator-authority co-metric, enforced at torque level by a quadratic program in the allocation null space. A single design inequality renders the certified set compact and strictly interior to the actuator box, with the readiness cost of any rotor deactivation given in closed form as $\ln(n/(n{-}m))$ for symmetric designs. Tracking is sacrificed only through an explicit alignment ratio, with wrench error bounded by $\mathcal{O}(ρ^{-1/2})$ and a robust variant handles motor-parameter uncertainty with a closed-form floor shift independent of the airframe matrix. On a hexarotor and a fully-actuated octorotor the closed-form gap matches simulation to machine precision; in the authority-scarce regime greedy maximization violates the certified floor and commits wrench errors up to eighty times larger than the proposed filter, which holds invariance of the certified set at negligible tracking cost.

Problem

• Overactuated Multirotor
• Control Allocation
• Readiness Barrier Functions
• Forward-Invariant Control Authority

Innovation

• Readiness Barrier Functions
• Forward-Invariant Control Authority
• Overactuated Multirotor Allocation
• Null-Space Quadratic Program
• Closed-Form Robustness