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Visual positioning technology of picking robots for dynamic litchi clusters with disturbance

Xiong, Juntao, He, Zhiliang, Lin, Rui, Liu, Zhen, Bu, Rongbin, Yang, Zhengang, Peng, Hongxing, Zou, Xiangjun
Computers and electronics in agriculture 2018 v.151 pp. 226-237
Litchi, cameras, fruits, orchards, robots
Visual localization by picking robots in natural environments is a difficult problem due to disturbance by interference factors. To solve this problem, research on visual positioning for dynamic litchi clusters with disturbance under natural environments was performed in this study. A visual system with two CCD cameras was used to acquire images of dynamic litchi clusters. The centroid of minimum bounding rectangle of litchi fruit was calculated, and the pendulum principle was used to calculate the oscillation angle of litchi clusters with three disturbance states: static, slight and large. For static or slight disturbance, the improved fuzzy C-means clustering method was used in image segmentation to obtain the litchi fruit and stem, and picking points were calculated using binocular visual stereo matching. The indoor experimental results show the maximum depth error of the picking point visual positioning for litchi clusters with static or slight disturbance is 5.08 cm, and the minimum depth error is 1.96 cm. The orchard visual positioning test results show the maximum depth error is 5.8 cm, and the minimum depth error is 0.4 cm. The results meet the picking demands of the picking robot end effector.