グラップルローダを用いた丸太積み込み作業における熟練オペレータによる機械作業の特徴(<特集>伐採搬出の道具と機械) Characteristics of a log loading work with a grapple loader performed by a skilled operator(<SPECIAL ISSUE>Tools and machines for logging)

荷役作業中のグラップルローダの動きを解析することにより,能率的に作業を行うオペレータの機械操作技術や作業手法を明らかにすることを試みた。グラップルローダの動きを計測するため各アクチュエータにセンサを取り付け,その変位量をデータロガーに記録した。計測データから作業機の3次元座標位置を演算する精度は,平均誤差34.5mm,最大誤差80.2mm程度であり,作業を解析する上での精度としては十分に利用できることを確認した。技術レベルの異なるオペレータがはい積みされている丸太3.49m^3をフォワーダ荷台に積み込む作業について解析した結果,熟練者の生産性は初心者に比べて平均で2倍高く,機械操作について以下の特徴が見られた。1)作業機の移動範囲がコンパクトで無駄な動作がない,2)軌跡がスムーズな円弧を描き,複数個のアクチュエータを同時に操作している,3)丸太を把持する際には,常に丸太の重心付近を把持し吊り上げた材が安定している,4)油圧を有効に利用し,機械の能力を最大限に使っている。熟練者と初心者では,機械操作技術および作業手法に明確な違いがあり,そのことが作業の生産性に大きく影響している可能性が示唆された。

In this research, we attempted to clarify the effective machine control technique and working method of an expert worker by analyzing the motion of a grapple loader used in log loading work. In particularly, we focused on the locus of the grapple attachment, and thus installed sensors on each actuator of the knuckle boom for calculating the three-dimensional coordinates of the attachment. The average positioning error was 34.5 mm and the maximum error was 80.2 mm, both of which were considered adequately precise values for our analysis. We then investigated the task of loading 3.49 m^3 of logs on a forwarder carrier, as performed by two operators with different skill levels. As a result, we found that the productivity of work done by the expert was about two times higher than that by the beginner. A close examination of the operations clarified the expert's characteristic technique that contributed to high productivity as follows: 1) the work space was compact, and there was no unnecessary movement; 2) multiple actuators were operated simultaneously, and the attachment was maintained along the most efficient path; 3) the logs were handled stably by being gripped at their center of gravity; and 4) the machine's power was used effectively and continuously during the work. An apparent difference in the operating skills between the beginner and expert has been suggested, and that difference could cause the difference in productivity.