Observability-Aware Control for Quadrotor Formation Flight with Range-only Measurement

Cooperative Localization (CL) is a promising approach to achieve safe quadrotor formation flight through precise positioning via low-cost inter-drone sensors. This paper develops an observability-aware control principle tailored to quadrotor formation flight with range-only inter-drone measurement. The control principle is based on a novel approximation of the local observability Gramian (LOG), which we name the Short-Term Local Observability Gramian (STLOG). The validity of STLOG is established by a proof of the link between local observability and estimation precision. We propose the Observability Predictive Controller (OPC), an implementation of our control principle under a receding-horizon framework, which optimizes a metric of the STLOG to maximize the minimum precision improvement along a trajectory. Monte Carlo simulations and experimental flight tests are conducted on a pair of quadrotors performing formation flight. The results show that the OPC improves positioning precision and estimator confidence, confirming the practical utility of the proposed approach.