Optimization of a Spatial Transmission Linkage for Heavy Manipulators

Abstract

The problem described in this paper is part of the development of a hydraulically driven heavy manipulator at the IMECH GmbH. The manipulator is intended for handling payloads up to 500 kilograms in a constrained environment. Therefore it is necessary to equip the manipulator with redundant degrees of freedom – which means more than six in the spatial case. On the other hand, in contrast to existing large manipulators (Wanner, 1990), the size of the manipulator is limited. Consequently it is difficult to provide as many joints as there are degrees of freedom, which leads to the idea of using spherical joints to replace three rotational joints. A spatial transmission linkage is necessary to control the movement of the spherical joint, since the swivel motion covers an angle up to 205°. The complete manipulator is built up of modular components, called ball-joint-units consisting of a central spherical joint and a transmission linkage. A brief description of a ball-joint-unit is given in section 2