A system allowing both the automatic programming of a robotic cell and the monitoring of assembly task execution is described. The system consists of a coordinator, a set of specialists and a task supervisor. The specialists are each associated with a particular snbtask within the assembly and have both off-line and on-line functions. The three specialists which have been incorporated into the system are grasping, displacement and insertion-The coordinator works from a task-level description of the assembly to he performed and generates a cell-centered plan based on an ordered call to the system specialists. Once the assembly operation has been planned, it is the respcmsibility of the supervisor to monitor the correct execution of the assembly task by handling multisensory integration, correcting local errors and calling--when needed--the on-line functions of the several specialists. The overall operation of the system is illustrated by means of an assembly task example.
INTRODUCTIONThe application of robots in mechanical assembly tasks is a field of growing interest. Nevertheless, several open problems in the programming and execution phases of these tasks currently limit their practical industrial use. This is clear when considering that even the simplest assembly tasks require the coordinated action of different object-oriented planning systems, each of them being associated with a given elementary assembly operation. 4 Grasping,17 displacement I a and insertion t ~ constitute three examples of such elementary operations arising in most assembly tasks. Each one of these elemental planning systems has been independently studied by many research teams, 9" ~ 0. ~ 5 The results obtained so far seem to indicate the extreme complexity of this kind of apparently simple operation.
