Cooperative Localization is a promising approach to achieving 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 measurements. 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 proving its link to directional estimation precision in nonlinear systems. We propose the Observability Predictive Controller (OPC), a receding-horizon controller that generates optimal inputs to enhance information gain in weakly observable state directions by maximizing the minimum eigenvalue of the STLOG. This reduces the risk of estimator divergence due to the unbounded growth of uncertainty in weakly observed state components. Monte Carlo simulations and flight experiments are conducted with quadrotors in a GNSS-denied ferrying mission, showing that the OPC improves positioning confidence and estimator robustness.

翻译：协同定位是一种通过低成本无人机间传感器实现精确定位，从而实现安全四旋翼编队飞行的有效方法。本文针对仅使用无人机间距离测量的四旋翼编队飞行，提出了一种可观测性感知控制原理。该控制原理基于一种新颖的局部可观测性格拉姆矩阵近似方法，我们将其命名为短期局部可观测性格拉姆矩阵。通过证明其与非线性系统中方向估计精度的关联，确立了STLOG的有效性。我们提出了可观测性预测控制器，这是一种滚动时域控制器，通过最大化STLOG的最小特征值来生成最优控制输入，以增强弱可观测状态方向的信息增益。这降低了由于弱观测状态分量不确定性无界增长而导致估计器发散的风险。在GNSS拒止的运输任务中，对四旋翼无人机进行了蒙特卡洛仿真和飞行实验，结果表明OPC提高了定位置信度和估计器鲁棒性。