Development of a Chainsaw with Branch Bite Preventing Mechanism for Pruning Robots

Abstract

When forestry workers prune away and lop branches off a tree using a chainsaw, they do so from various directions considering the possible deflection of the branches to prevent branch-bite. When using a robot with a chainsaw attached, it may get stuck halfway due to branch-bite caused by cutting in one direction. This paper formulates the contact force where a branch is cut at the contact point between the guide bar and the branch, and estimates the required driving force for the robot to cut and proceed. Experiments were conducted using a branch cutting machine that reproduces branch-bite to compare the currents flowing in the driving motor for the cases with and without an anti-branch-bite mechanism. The currents measured for the case with and without the anti-branch-bite mechanism were 85.5±17.2 and 148.9±20.7 mA, respectively. A significant test (Man-Whitney U-test, p<0.05) was conducted and it shows that the proposed mechanism outperforms the conventional one. The proposed branch-bite prevention mechanism was shown to prevent branch-bite effectively and reduce the reaction force received when cutting and proceeding by spreading the incision of the branch using circular orbit cutting.