ABSTRACT

In the Nordic countries, trees are typically bucked into logs using harvesters that measure only a two-dimensional diameter profile of the stem. Because the value of a log can vary significantly depending on its shape and internal defects, bucking decisions can in principle be improved by optical scanning of the three-dimensional stem shape, and detection of knots and other features inside the stem by X-ray computed tomography (CT). The objective of this study was to quantify how much the value recovery at a sawmill could be increased, if bucking decisions took advantage of additional measurement data and a sawing simulator to estimate log values. A simulation study on 1582 Scots pine stems was performed to compare bucking based on a two-dimensional diameter profile with bucking that maximises log value based on either optical scanning alone, or both optical and CT scanning. For log positioning, both the traditional “horns-down” position, and value-maximising rotation based on CT scanning were considered. The results show that bucking based on optical scanning alone can potentially increase the value of sawn timber by up to 5%, and CT scanning before bucking provides little additional value for a sawmill using a CT scanner to optimise log rotation.

摘要

在北欧国家，通常使用仅测量茎的二维直径轮廓的收割机将树木推倒成原木。由于原木的值可能会因其形状和内部缺陷而发生很大变化，因此原则上可以通过光学扫描三维茎形状并通过计算X射线检测茎内部的打结和其他特征来改善屈曲决策。断层扫描（CT）。这项研究的目的是量化锯木厂的价值回收率，如果通过决策获得额外的测量数据和锯木模拟器来估算原木价值，锯木厂可以提高多少价值。进行了1582个苏格兰松树茎的模拟研究，以比较基于二维直径轮廓的屈曲与仅基于任一光学扫描的使对数值最大化的屈曲，或同时进行光学和CT扫描。对于原木定位，既考虑了传统的“降低角度”位置，又考虑了基于CT扫描的最大旋转值。结果表明，仅基于光学扫描的翘曲可以将锯材的价值提高多达5％，并且在翘曲之前进行CT扫描对于使用CT扫描仪优化原木旋转的锯木厂几乎没有任何附加价值。