In this paper, we present a fast, lightweight odometry method that uses the Doppler velocity measurements from a Frequency-Modulated Continuous-Wave (FMCW) lidar without data association. FMCW lidar is a recently emerging technology that enables per-return relative radial velocity measurements via the Doppler effect. Since the Doppler measurement model is linear with respect to the 6-degrees-of-freedom (DOF) vehicle velocity, we can formulate a linear continuous-time estimation problem for the velocity and numerically integrate for the 6-DOF pose estimate afterward. The caveat is that angular velocity is not observable with a single FMCW lidar. We address this limitation by also incorporating the angular velocity measurements from a gyroscope. This results in an extremely efficient odometry method that processes lidar frames at an average wall-clock time of 5.64ms on a single thread, well below the 10Hz operating rate of the lidar we tested. We show experimental results on real-world driving sequences and compare against state-of-the-art Iterative Closest Point (ICP)-based odometry methods, presenting a compelling trade-off between accuracy and computation. We also present an algebraic observability study, where we demonstrate in theory that the Doppler measurements from multiple FMCW lidars are capable of observing all 6 degrees of freedom (translational and angular velocity).

翻译：本文提出一种快速轻量级的里程计方法，利用调频连续波（FMCW）激光雷达的多普勒速度测量值，无需进行数据关联。FMCW激光雷达是近年来新兴的技术，能够通过多普勒效应测量每次回波的相对径向速度。由于多普勒测量模型相对于六自由度车辆速度呈线性关系，我们可构建线性连续时间速度估计问题，再通过数值积分获得六自由度位姿估计。其限制在于单个FMCW激光雷达无法观测角速度，为此我们引入陀螺仪的角速度测量值加以弥补。该方法极为高效，单线程处理激光雷达帧的平均实时耗时为5.64毫秒，远低于被测激光雷达10Hz的工作频率。基于真实行车序列的实验表明，与当前最先进的基于迭代最近点（ICP）的里程计方法相比，本方法在精度与计算量之间取得了极具竞争力的平衡。此外，我们通过代数可观性分析从理论上证明：多个FMCW激光雷达的多普勒测量值可完整观测全部六个自由度（平移速度与角速度）。