A comparison of the required energy in loadingfor

In automating an excavation task it is required to deene a nominal trajectory for the motion of the excavator tool, so that its motion can be programmed and controlled. During the motion, the excavating tool (the bucket for instance, in the case of a loader), experiences the excavating forces that must be overcome by the active forces for moving the bucket, in order for the excavation to take place. The excavating forces depend not only on the characteristics of the media to be excavated, the tool itself and the operation (combination of cutting, digging and scooping), but on the trajectory selected for the tool, as well. Moreover, the energy consumed during the excavation process is related to the forces and the trajectory. The importance of a proper trajectory becomes more evident considering that such an operation is repeated many many times. In the long run, the associated cost depends on the consumed energy and the speed at each operation. This paper is concerned with the required energy for loading by a bucket in a loader, or a load-haul-dump unit in underground mines. A number of diierent techniques or trajectories have been proposed for the motion of a bucket, as the loading strategy. In this paper the excavation forces and the approximate energy required for lling a bucket by moving it according to the proposed strategies are compared.