Addressing the inherent low acquisition frequency limitation of 3D LiDAR to achieve high-frequency output has become a critical research focus in the LiDAR-Inertial Odometry (LIO) domain. To ensure real-time performance, frequency-enhanced LIO systems must process each sweep within significantly reduced timeframe, which presents substantial challenges for deployment on resource-constrained platforms. To address these limitations, we introduce SR-LIO++, an innovative LIO system capable of achieving doubled output frequency relative to input frequency on resource-constrained hardware platforms, including the Raspberry Pi 4B. Our system employs the previously proposed sweep reconstruction methodology to enhance LiDAR sweep frequency, generating high-frequency reconstructed sweeps. Building upon this foundation, we propose a caching mechanism for intermediate results (i.e., surface parameters) of the most recent segments, effectively minimizing redundant processing of common segments in adjacent reconstructed sweeps. This method decouples processing time from the traditionally linear dependence on reconstructed sweep frequency. Furthermore, we present a quantized map point management based on index table mapping, significantly reducing memory usage by converting global 3D point storage from 64-bit double precision to 8-bit char representation. This method also converts the computationally intensive Euclidean distance calculations in nearest neighbor searches from 64-bit double precision to 16-bit short and 32-bit integer formats, reducing computational cost. Extensive experimental evaluations across three distinct computing platforms and four public datasets demonstrate that SR-LIO++ maintains state-of-the-art accuracy while substantially enhancing efficiency. Notably, our system successfully achieves 20 Hz state output on Raspberry Pi 4B hardware.

翻译：针对三维激光雷达固有低采集频率限制以实现高频输出的问题，已成为激光雷达-惯性里程计（LIO）领域的关键研究焦点。为确保实时性能，频率增强型LIO系统必须在显著缩短的时间窗口内完成每次扫描处理，这对资源受限平台上的部署提出了重大挑战。为突破这些限制，我们提出SR-LIO++这一创新LIO系统，能够在包括树莓派4B在内的资源受限硬件平台上实现相对于输入频率两倍的输出频率。该系统采用前期提出的扫描重建方法提升激光雷达扫描频率，生成高频重建扫描。在此基础上，我们提出针对最近片段中间结果（即表面参数）的缓存机制，有效减少相邻重建扫描中公共片段的冗余处理。该方法将处理时间从传统上与重建扫描频率的线性依赖关系中解耦。此外，我们提出基于索引表映射的量化地图点管理方案，通过将全局三维点存储从64位双精度转换为8位字符表示，显著降低内存占用。该方法还将最近邻搜索中计算密集的欧氏距离计算从64位双精度转换为16位短整型和32位整型格式，降低了计算成本。在三个不同计算平台和四个公开数据集上的广泛实验评估表明，SR-LIO++在保持最先进精度的同时大幅提升了效率。值得注意的是，我们的系统在树莓派4B硬件上成功实现了20Hz的状态输出。