基于ISS-LCG组合特征点的油菜分枝点云配准方法

【目的】针对传统点云配准方法准确率低、速度慢等问题，以油菜Brassica napus L.分枝点云为研究对象，提出基于ISS-LCG组合特征点的配准方法。【方法】以成熟期油菜角果分枝点云为对象，去除背景噪声后，得到清晰完整的油菜分枝点云；然后通过内部形状描述子(Intrinsic shape signature,ISS)提取油菜分枝点云的特征点，再使用线性同余法(Linear congruential generator,LCG)伪随机选取油菜点云的部分点构成关键点，将特征点和关键点进行融合，构成ISS-LCG组合特征点；通过三维形状上下文特征(3D shape context,3DSC)对组合特征点进行特征描述，最后采用RANSAC+ICP两步点云配准法进行点云配准。【结果】基于ISS-LCG组合特征点的点云配准算法以30°为间隔对点云进行两两配准时，配准效果最佳，配准误差约0.066 mm，配准精度比未采用组合特征点的配准方法提升了50%～70%；配准时间均小于48 s，平均配准时间为8.706 s。【结论】该方法在可控环境内可以实现成熟期油菜植株高精度、高效率的自动配准。

Point cloud registration method of rape branches based on ISS-LCG combined feature points

Objective Aiming at the problems of low accuracy and slow speed of traditional registration methods, we took point cloud of rape (Brassica napus L.) branches as the research object, and proposed a registration method based on ISS-LCG combined feature points.Method The pods of mature rape branches were taken as the research object. The background noise of rape point cloud was removed to obtain the clear and complete point cloud of rape branches. Intrinsic shape signatures (ISS) algorithm was used to extract feature points of point cloud. Linear congruential generator (LCG) algorithm was used to pseudo-randomly select some points of point cloud to constitute key points. Feature points and key points were combined to form ISS-LCG combined feature points. Then, the combined feature points were described by 3D shape context (3DSC) algorithm. Finally, RANSAC + ICP two-step point cloud registration method was used for point cloud registration.Result The precision of on-time registration of rape branch point cloud in pairwise matching was the highest among shooting angles with an interval of 30°. The registration error was about 0.066 mm. Compared with the method without combined feature points, the registration accuracy was improved by 50%-70%. The registration time was less than 48 s, and the average registration time was 8.706 s.Conclusion The proposed method could achieve highly precise and efficient automatic registration of mature rape plants in a controlled environment.