Towards a Vision System for Supervising Assembly Processes

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Towards a Vision System for Supervising Assembly Processes ?
Christian Bauckhage, Jannik Fritsch, Franz Kummert, Gerhard Sagerer??
Technische Fakultat, AG Angewandte Informatik, University of Bielefeld P.O. Box 100131 33501 Bielefeld Germany
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to recognize assembled objects in image data is presented in section 4. Section 5 describes the approach to detect actions occurring during the construction and section 6 illustrates how the results of these modules can be fused in order to cope with incomplete or inconsistent information. An approach towards an incremental recognition of assemblies, i.e. a recognition strategy augmenting earlier resul7.
Abstract. Supervising robotic assembly of multi-functional objects by means of a computer vision system requires components to identify assembly operations and to recognize feasible assemblies of single objects. If the results of both components should be consistent there have to be common models providing knowledge about the intended application. However, if the assembly system should handle not only exactly speci ed tasks it is rather impossible to model every possible assembly or action explicitly. Therefore, based on a exible approach to model and recognize bolted assemblies and a method to monitor a construction process we propose an approach to fuse the results of the action detection and the recognition of assemblies in order to realize a reliable and e cient supervision.
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This work was supported by the German Research Foundation (DFG) within Collaborative Research Project 360. Email: fcbauckha,jannik,franz,sagererg@techfak.uni-bielefeld.de
a) b)
Fig. 1.: Examples of assembled Bau x objects and the model of the airplane that the arti cial communicator is to construct in cooperation with a human instructor.
2 System Overview
The scene in which all construction actions are carried out consists of a table and is modi ed by the robot or the user. A Camera is mounted in an angle of 45 degrees above the table to obtain images of the scene.
In Proc. Symposium on Intelligent Robotic Systems (SIRS’99), pages 89-98, Coimbra, 1999.
Published in Symposium on Intelligent Robotic Systems, pp. 89-98, Coimbra, Portugal, 1999
1 Introduction
Assembling a complex object from a set of separate parts usually takes a sequence of assembly operations, i.e. in most cases constructing an assembly is a process of sequentially connecting several components. Whenever a computer vision system is used to supervise such a process, the problem of modeling assembled objects arises. Recognizing the intermediary results of an assembly process requires knowledge about the way single objects can be put together to form feasible assemblies. Furthermore, possible actions which may occur during the construction have to be represented so that assembly operations are detectable. The work presented here is conducted within a research project studying advanced human-machine communication intended to develop a \Situated Arti cial Communicator" which is able to manipulate objects in its environment according to the instructions of a human. The domain was chosen to be the cooperative construction of a toy-airplane using parts of a wooden construction-kit for children. Figure 1a) shows some of the Bau x objects and indicates the manner of construction while the model of the airplane which is a possible of the construction can be seen in Fig. 1b). A speci c constraint characterizing the work in this project is that the system should simulate a human constructor: it should only employ sensors similar to human senses and only two manipulators are allowed. Thus, the machinery in operation is a two-handed robot which processes visual and auditory input and can be instructed using natural speech and gestures, i.e. like one would instruct a human constructor 4]. Besides robotic components to manipulate the objects and modules to recognize verbal or gestural instructions our system necessarily requires a component to supervise and memorize the ongoing assembly actions. In this paper we describe two approaches which cover di erent aspects of a construction task. On the one hand sequential mechanical assembly means consecutively executing assembly operations so that monitoring all the actions in the construction environment provides information about the state of the assembly process. On the other hand some of the operations during this process result in assemblies which later on will become subassemblies of even more complex objects. Analyzing the structure of these intermediate constructions informs about the process, too. In order to get a consistent interpretation of the ongoing actions the observations made from these di erent viewpoints have to be fused and consequently, a reliable interpretation of the event in the construction environment is possible. First, section 2 presents a detailed depiction of the scenario and describes how di erent modules of the system interact to monitor assembly operations. In section 3 we introduce di erent techniques to represent assembled objects suitable for our purpose. The use of these techniques to realize a knowledge based approach