Integration of an expert system and dynamic programming approach to optimize log breakdown using 3-dimensional log and internal defect shape information Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/00000275g

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  • A computer program, SAW3DG, was developed to optimize log breakdown using 3-dimensional log and internal defect shapes. The program was based on SAW3D, a log breakdown optimization program considering only 3-dimensional log shape. SAW3D was modified to include internal log defects in 3-dimensional representation and integrated with SLGRADER, an expert system for softwood lumber grading, resulting in a system that is able to optimize log breakdown based on lumber grade. SAW3DG allows live, cant, around, and multi-thickness sawing methods. The system uses a polygonal cross-section model to represent the log and its internal defects. It consists of four basic components: headrig optimization, edging optimization, trimming optimization, and lumber grading. The headrig optimization component begins the log breakdown process by mathematically rotating and skewing the log into a position and then uses a programming (DP) algorithm to find the optimum sawing pattern. The profile of each piece cut from the log along with its defect information is then passed to the edging optimization component where the piece is optimally positioned and then edged using another DP algorithm. Information about the untrimmed lumber and its defects is sent to the trimming optimization component where the sizes of each finished piece of lumber and defects exposed on its four faces are finally determined. This information is then sent to the lumber grading component to determine the lumber grade. Lumber value is determined by its grade and size and used by a third DP algorithm to decide the optimum trimming pattern. Solutions are provided both in text and graphic formats. Twelve computer generated logs of various sizes and in ellipsoid, horn-down, and S-twisted shapes with a number of internal defect types and distributions were used to evaluate SAW3DG. Results indicated that SAW3DG provided better solutions than those models that consider only the true external log shape or that treat the log as a defect free truncated cone. In addition, effects of log rotation and skewing operations, flitch/cant pitch, and different sawing methods on SAW3DG solutions were also studied.
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