Simplifying synchronization in cooperative robot tasks-an enhancement of the manipulation primitive paradigm

Abstract

Complex handling and assembly tasks can be gradually decomposed into simpler sub-tasks until a level of elementary 'primitive' tasks is reached, which can be expressed generically by so-called Manipulation Primitives. Manipulation Primitives can hence be utilized as the foundation of a unified paradigm to specify and execute complex sensor-based robot tasks. By embedding these Manipulation Primitives into a fully hierarchical structure, the specification and reuse of common sub-tasks can be simplified immediately. However, without appropriate synchronization mechanisms the user-friendly and effective specification of tasks for multi-robot systems based on Manipulation Primitives still remains an issue. The underlying place-transition net formalism allows for synchronization by including the notions of forks and joins into the net but this approach is neither user-friendly nor does it allow for immediate support of more sophisticated synchronization mechanisms such as range synchronization. To eliminate this drawback of the Manipulation Primitive Concept, this contribution proposes powerful but at the same time easy-to-use synchronization primitives and introduces a revised Manipulation Primitive paradigm, which takes full advantage of the developed primitives. The advantages of the proposed concepts regarding the specification of tasks for industrial multi-robot systems are illustrated with several examples.