基于激光雷达的农业耕作微地貌测量装置设计与试验

Design and Experiment of Microtopography Measuring Device for Agricultural Cultivation Based on LiDAR

针对现有地表微地貌测量装置难以兼顾农业耕种作业后地表微地貌测量的精度和效率、部分测量装置单次测量覆盖区域不能满足统计要求的问题,设计了一套由激光雷达、直线导轨、便携式计算机和支架等构成的非接触式地表微地貌测量装置,开发了以STM32单片机为核心的步进电机驱动控制器,并与上位机软件形成整套采集系统,可实现激光雷达精确定位并快速获取地表三维坐标。该装置典型分辨率在激光雷达扫描方向为3.8~10mm,垂直扫描方向可在毫米精度范围内任意设置,测距分辨率为1mm;测量区域覆盖面积典型值为6.8m2,垂直扫描方向分辨率为10mm时,单次测量时间低于2.5min。通过分析测量误差来源,建立了系统误差补偿模型,在15次均值滤波的条件下,该装置测量最大绝对误差为2.7mm,最大平均绝对误差为0.9mm。油菜机械直播后地表微地貌测量试验结果表明:利用Matlab生成的地表三维模型可以精确地重构原有地表微地貌特征,测量结果与实际地表高度变化吻合度较高;测量数据统计结果表明,固定区域内均方根高度和相关长度测量值需分别在16次和64次的等距采样下达到稳定均值,而畦沟相关评价参数也需要多组样本计算才具有统计意义。

Aiming at the fact that the existing surface microtopography measuring device is difficult to achieve the accuracy and efficiency of surface measurement simultaneously after mechanical cultivation operations,a non-contact surface microtopography measuring device composed of LiDAR,linear guide,portable computer and bracket was developed.The stepping motor drive controller based on STM32 single-chip microcomputer was developed,and a complete acquisition system was built up combined with the upper computer software.The system can realize precise positioning of the LiDAR and quickly obtain the three-dimensional coordinates of the surface.The typical resolution of the device was 3.8~10 mm in the LiDAR scanning direction,the vertical scanning direction can be arbitrarily set within the millimeter precision range,the ranging resolution was 1 mm;the coverage area was 6.8 m 2 typically,when the vertical scanning direction resolution was 10 mm,the single measurement time was less than 2.5 min.By analyzing the source of measurement error,the system error compensation model was established.Under the condition of 15 mean filtering,the maximum absolute error of the device was 2.7 mm and the maximum average absolute error was 0.9 mm.The device was investigated on rapeseed surface area after direct seeding of the crop.Test results revealed that the surface three-dimensional model generated by Matlab can accurately reconstruct the original microtopography surface features,and the measurement results were consistent with the actual surface height fluctuation.The statistical analysis showed that for attaining stable results,the root mean square height and the correlation length in the fixed size area needed to be sampled 16 times and 64 times,respectively.