Evaluation of the use of box size priors for 6D plane segment tracking from point clouds with applications in cargo packing

Abstract

Available solutions to assist human operators in cargo packing processes offer alternatives to maximize the spatial occupancy of containers used in intralogistics. However, these solutions consist of sequential instructions for picking each box and positioning it in the containers, making it challenging for an operator to interpret and requiring them to alternate between reading the instructions and executing the task. A potential solution to these issues lies in a tool that naturally communicates each box's initial and final location in the desired sequence to the operator. While 6D visual object tracking systems have demonstrated good performance, they have yet to be evaluated in real-world scenarios of manual box packing. They also need to use the available prior knowledge of the packing operation, such as the number of boxes, box size, and physical packing sequence. This study explores the inclusion of box size priors in 6D plane segment tracking systems driven by images from moving cameras and quantifies their contribution in terms of tracker performance when assessed in manual box packing operations. To do this, it compares the performance of a plane segment tracking system, considering variations in the tracking algorithm and camera speed (onboard the packing operator) during the mapping of a manual cargo packing process. The tracking algorithm varies at two levels: algorithm (Awpk), which integrates prior knowledge of box sizes in the scene, and algorithm (Awoutpk), which assumes ignorance of box properties. Camera speed is also evaluated at two levels: low speed (Slow) and high speed (Shigh). This study analyzes the impact of these factors on the precision, recall, and F1-score of the plane segment tracking system. ANOVA analysis was applied to the precision and F1-score results, which allows determining that neither the camera speed-algorithm interactions nor the camera speed are significant in the precision of the tracking system. The factor that presented a significant effect is the tracking algorithm. Tukey's pairwise comparisons concluded that the precision and F1-score of each algorithm level are significantly different, with algorithm Awpk being superior in each evaluation. This superiority reaches its maximum in the tracking of top plane segments: 22 and 14 percentage units for precision and F1-score metrics, respectively. However, the results on the recall metric remain similar with and without the addition of prior knowledge. The contribution of including prior knowledge of box sizes in (6D) plane segment tracking algorithms is identified in reducing false positives. This reduction is associated with significant increases in the tracking system's precision and F1-score metrics. Future work will investigate whether the identified benefits propagate to the tracking problem on objects composed of plane segments, such as cubes or boxes.