基于修正似然滤波的无人机编队相对导航方法

针对无人机编队相对导航系统中视觉导航传感器量测数据存在随机时延问题，提出一种能够处理多步随机延迟量测的修正似然容积卡尔曼滤波（ML-CKF）算法。用多个伯努利随机变量对量测模型进行修正以描述随机延迟；通过边缘化延迟变量来计算滤波的似然函数以从延迟量测中提取准确的信息；采用三阶球面-径向容积准则计算高斯加权积分以解决系统的非线性。滤波中的加权因子根据接收量测的特性进行调整，因此，所提修正似然滤波具有自适应卡尔曼滤波属性。利用罗德里格斯参数表示姿态误差，设计了基于修正似然容积卡尔曼滤波的相对导航滤波器。仿真结果表明：所提算法可以准确地估计出长机和僚机之间的相对位置、速度和姿态，且估计精度高于容积卡尔曼滤波和传统随机时延滤波。

Relative navigation method based on modified likelihood filtering for unmanned aerial vehicle formation

A modified likelihood cubature Kalman filtering (ML-CKF) is proposed to solve the problem that the measurements of vision-based relative navigation sensor for unmanned aerial vehicle formation are randomly delayed by multiple steps. The measurement model is modified by the Bernoulli random variables to describe the random delay. The likelihood function of the filtering is calculated by marginalizing out the delay variable to extract accurate information from the delayed measurements. The third-degree spherical-radial rule is utilized to compute the Gaussian-weighted integrals for the nonlinear system. The proposed modified likelihood filtering has the property of adaptive filtering because the weighting factors of the filtering are tuned based on the characteristics of the received measurements. By utilizing the Rodrigues parameters to denote the attitude errors, the relative navigation filter of unmanned aerial vehicle formation is designed based on the ML-CKF. Simulation results indicate that the proposed filtering algorithm could accurately estimate the relative position, velocity and attitude between the leader and follower. Moreover, the estimation accuracy of ML-CKF is superior to cubature Kalman filtering and conventional randomly delayed filtering.