Pruning tree-branches close to electrical power lines using a skew-gripper and a multirotor helicopter

In this paper, a solution for pruning tree branches close to electric power lines using a hexarotor helicopter equipped with a circular saw and a robotic gripper is proposed. The solution consists of flying to the target, in this case the branch to be pruned, fix the helicopter to it and finally, prune the tree branch with a circular saw. In this first approach, we propose a novel skew-gripper design which assists the helicopter in both tasks, grasping and pruning. Taking advantage of a rotational motion created by the motors of the gripper, the body of the helicopter is able to turn around the branch for cutting it by means of a circular saw. Moreover, we propose to control the speed of the circular saw by using only the back-EMF (Electromotive Force) as a feedback control signal without the necessity of using encoders or tachometers.