A Pragmatic Approach to Exploiting Full Force Capacity for Serial Redundant Manipulators

Abstract

Assembly and drilling tasks are commonly allocated to robots in the production industry, and are often operations where the manipulator holds a static configuration while the end-effector physically interacts with the environment. Carrying its own weight while countering forces may be too much for a limited payload robot in certain configurations. Kinematic redundancy with regard to a task allows a robot to perform it in a continuous space of articular configurations; space in which the payload of the robot may vary dramatically. It may be impossible to hold a physical interaction in some configurations, while it may be easily sustainable in others that bring the end-effector to the same location. This paper describes a framework for this kind of operations, in which kinematic redundancy is used to explore the full extent of a force capacity for a given manipulator and task. A pragmatic force capacity index is proposed. This index offers a sound basis for redundancy resolution via optimization or complete redundancy exploration, and may provide good hints for end-effector design. A practical use case with a 7-axis KUKA LBR iiwa was used to demonstrate the relevance of the proposed method.