Task-oriented approaches to the inverse kinematics problem for a reclaimer excavating and transporting raw material

The inverse kinematics problem of the reclaimer that excavates and transports raw materials in a raw yard is investigated. Link coordinates are introduced by the Denavit-Hartenberg representation. The middle bucket, among the buckets which are in contact with the raw material pile, is treated as the end-effector of a reclaimer. Two task-oriented approaches are investigated. The first approach assumes the complete removal of a pile via a level plan on the pile. In this case, the end-effector is assumed to be a particle moving in the three-dimensional (3D) space. A closed-form solution is provided. The second approach assumes the reclamation of an arbitrary pile. The end-effector is regarded as a rigid body which requires both position and orientation information. Because there is no solution for the second approach in general, an approximate solution is provided by exploiting a geometric constraint. The 3D information near the excavation point is approximated as a plane and the orientation of the end-effector is given in the normal direction of the plane.