On the Comparison of Gauge Freedom Handling in Optimization-Based Visual-Inertial State Estimation
On the Comparison of Gauge Freedom Handling in Optimization-Based Visual-Inertial State Estimation
复制标题
基于优化的视觉惯性状态估计中规范自由度处理的比较
DOI：
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发表时间：
2018
影响因子：
5.2
通讯作者：
D. Scaramuzza
中科院分区：
文献类型：
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作者：
Zichao Zhang;Guillermo Gallego;D. Scaramuzza
众所周知，视觉惯性状态估计可以达到四个自由度（DoF）变换（围绕重力旋转和平移），并且必须正确处理额外的自由度（“测量自由度”）。虽然在实践中采用了不同的方法来处理量规自由度，但尚未有研究系统地分析它们之间的差异。在本文中，我们首次对基于优化的视觉惯性状态估计中处理量规自由度的不同方法进行了比较分析。我们通过实验比较了三种常用的方法：将不可观察状态固定为某些给定值，在这些状态上设置先验，或者在优化过程中让状态自由演化。具体而言，我们表明：1)三种方法的精度和计算时间相似，自由量规方法略快；2)自由规范法的协方差估计表面上有很大的不同，但实际上与其他方法密切相关。我们的研究结果在模拟和现实世界的数据集上都得到了验证，可以用于设计基于优化的视觉惯性状态估计算法。
It is well known that visual-inertial state estimation is possible up to a four degrees-of-freedom (DoF) transformation (rotation around gravity and translation), and the extra DoFs (“gauge freedom”) have to be handled properly. While different approaches for handling the gauge freedom have been used in practice, no previous study has been carried out to systematically analyze their differences. In this letter, we present the first comparative analysis of different methods for handling the gauge freedom in optimization-based visual-inertial state estimation. We experimentally compare three commonly used approaches: fixing the unobservable states to some given values, setting a prior on such states, or letting the states evolve freely during optimization. Specifically, we show that 1) the accuracy and computational time of the three methods are similar, with the free gauge approach being slightly faster; 2) the covariance estimation from the free gauge approach appears dramatically different, but is actually tightly related to the other approaches. Our findings are validated both in simulation and on real-world data sets and can be useful for designing optimization-based visual-inertial state estimation algorithms.