arXiv subjects

Craig A. Woolsey

Publications and source records attributed to Craig A. Woolsey.

4 recordsLinked to original sources

arXiv2026

Practical Complete Tracking With Pivoted Unidirectional Actuation

This paper addresses practical tracking control for robotic vehicles with pivoted unidirectional actuators. A widely recognized obstacle to tracking control for multirotors is the free-fall singularity --- when commanded to free-fall, the vehicle's attitude target becomes undefined. This singularity is a pathology pertinent to all robotic vehicles with pivoted and gimbaled unidirectional actuators. This paper addresses the planar instance of the general theoretical problem: the case of a vehicle with pivoted unidirectional actuation. Starting from a baseline robust controller that assumes unconstrained inputs, we redesign the control law to be compatible with the pivoted actuator. This is accomplished by driving the output of the pivoted actuator to a ball centered at the target input value. The baseline controller's guarantees are recovered in a practical sense. The theory is illustrated with a simulation example.

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arXiv2025

A Symmetry-Preserving Reduced-Order Observer

A symmetry-preserving, reduced-order state observer is presented for the unmeasured part of a system's state, where the nonlinear system dynamics exhibit symmetry under the action of a Lie group. Leveraging this symmetry with a moving frame, the observer dynamics are constructed such that they are invariant under the Lie group's action. Sufficient conditions for the observer to be asymptotically stable are developed by studying the stability of an invariant error system. As an illustrative example, the observer is applied to the problem of rigid-body velocity estimation, which demonstrates how exploiting the symmetry of the system can simplify the stabilization of the estimation error dynamics.

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arXiv2022

Robustness and Convergence Analysis of First-Order Distributed Optimization Algorithms over Subspace Constraints

This paper extends algorithms that remove the fixed point bias of decentralized gradient descent to solve the more general problem of distributed optimization over subspace constraints. Leveraging the integral quadratic constraint framework, we analyze the performance of these generalized algorithms in terms of worst-case robustness and convergence rate. The utility of our framework is demonstrated by showing how one of the extended algorithms, originally designed for consensus, is now able to solve a multitask inference problem.

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arXiv2020

Wind profiling in the lower atmosphere from wind-induced perturbations to multirotor UAS

We present a model-based approach to wind velocity profiling using motion perturbations of a multirotor unmanned aircraft system (UAS) in both hovering and steady ascending flight. A state estimation framework was adapted to a set of closed-loop rigid body models identified for an off-the-shelf quadrotor. The quadrotor models used for wind estimation were characterized for hovering and steady ascending flight conditions ranging between 0 and 2 m/s. The closed-loop models were obtained using system identification algorithms to determine model structures and estimate model parameters. The wind measurement method was validated experimentally above the Virginia Tech Kentland Experimental Aircraft Systems Laboratory by comparing quadrotor and independent sensor measurements from a sonic anemometer and two SoDARs. Comparison results demonstrated quadrotor wind estimation in close agreement with the independent wind velocity measurements. Wind velocity profiles were difficult to validate using time-synchronized SoDAR measurements, however. Analysis of the noise intensity and signal-to-noise ratio of the SoDARs proved that close-proximity quadrotor operations can corrupt wind measurement from SoDARs.

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