Executing assembly tasks specified by manipulation primitive nets

Abstract

Numerous scientific publications in the open literature show approaches for automatic assembly planning, automated robot programming, notations for the task frame formalism, robot control architectures for hybrid control methods, and respective experimental results in these areas. But there are still significant gaps between these individual fields. Considering the whole chain, from assembly planning via autonomous robot programming to the execution of complex robot tasks, the latter part of it is discussed in this paper: manipulation of primitive nets as output of task planning systems are decomposed into single manipulation primitives, which are subsequently used to generate parameters for hybrid control. A hybrid controller computes set-points for a joint position controller. Our aim is to define versatile interfaces between the mentioned disciplines, in order to close the gaps between them. Derived from the task-frame formalism, manipulation primitives constitute the base interface in this sense. After its description, the composition of manipulation primitive nets is described. Regarding the control architecture, the interpretation of manipulation primitives as atomic commands and the setting of unambiguous low level control parameters is discussed. Subsequently, the software architecture necessary to realize the complex control structure for compliant motion, is introduced. To highlight the meaning for practical implementations, several experimental results of sample assembly tasks are shown.