Algorithms and Automated Material Handling Systems Design for Stacking 3D Irregular Stone Pieces

摘要

The motive of this research is to develop a good stacking method with an\nautomatic material handling system and the procedures that can increase productivity,\nreduce production costs, and prevent labor injury. A diversity of products leads to a\nnumber of different kinds of stacking problems. Much research has been done focusing\non two-dimensional arrangement for rectangles, circles or irregular shapes, and threedimensional\nregular-shaped objects such as rectangular boxes. To solve stacking\nproblems, many algorithms such as the genetic algorithm, simulated annealing and other\nheuristic algorithms have been proposed.\nThe three-dimensional stacking problem has a practical application in the\ntransportation, manufacturing, and construction industries. There has been relatively little\nemphasis on three-dimensional irregular objects; however, stacking three-dimensional\nirregular objects has become more common in industry. In this thesis research, three\nheuristic algorithms are proposed to stack irregular stone pieces nested in a container\nwith multiple layers. Primary functions of the heuristic algorithms include three major\nparts. First, it approximates irregular shapes to a cluster of straight lines. Secondly, it\narranges the approximated angles one-by-one with the proposed step-by-step rule. Finally,\nit considers the weight of the stone pieces from the pixel calculation for reasons of stability. The first and second algorithms are based on the area and angle of the stone\npiece and the third one is based on the approximated weight of the stone.\nAn automatic real-time stacking system including pneumatic devices, sensors,\nrelays, a conveyor, a programmable logic controller, a robotic arm, and a vision system\nwas developed for this study. The algorithms developed were tested by this automatic\nstacking system for better utilization. Three performance measures were presented in the\nexperimental result.\nComparisons between the results from three proposed algorithms and that from\nthe bottom-back-left algorithm are made. Experimental data demonstrate that the\nutilizations and the stabilities of the three proposed algorithms are statistically better than\nthat of the bottom-back-left algorithm. However, the cycle times of the three proposed\nalgorithms have no statistical difference from that of the bottom-back-left algorithm. In\naddition, a statistical test between each proposed algorithm is also conducted. Both the\nutilizations and stabilities have statistical differences between each proposed algorithm\nwhile the cycle times do not. The results of this study show that the algorithm\ndeveloped works effectively for solving the stone-pieces stacking problem.