Category: CMUTR
Institution: Department of Computer Science, Carnegie
        Mellon University
Abstract: We have been developing a novel method to program a robot, 
        an APO(assembly-plan-from-observation) method.
        A human performs assembly operations in front of the APO 
        system's TV camera.
        The APO system recognizes such assembly operations and 
        generates an assembly plan to repeat the assembly operations
        using its robot arm.
        Since an important purpose of assembly operations is to achieve
        face contacts between objects, out previous system was based on
        face contact relations.
        Our system recognized object configurations after each of 
        assembly operation and then extracted face contact relations
        from the observed object configurations.
        By associating a face contact relation with the operation 
        necessary to achieve the relation, the system was able to 
        construct a plan to repeat the assembly.
        In this system, two kinds of information were extracted from 
        object configuration: 1) face-contact relation and 2) motion 
        parameters necessary to move objects around.
        The system works well while noise-free input.
        Usually, however, object configuration is contain some degree
        of error.
        Since a face contact relation is a topological relation, it can
        be obtained reasonably well from noisy object recognition 
        results.
        However, motion parameters are obtained directly by converting
        object configurations.
        Under the presence of error, due to error-contaminated motion
        parameters, the system may fail to perform an assembly 
        operation, although a face-contact relation and thus an 
        assembly operation is correctly recovered.
        This paper proposes a method to correct erroneous motion
        parameters based on a face contact relation.
        We assume that a given face contact relation reflects the 
        actual face contact correctly.
        Face contact constraint equations will be defined for each pair
        of contact faces.
        A face contact equation requires that a vertex of one face is 
        on the plane including the other face.
        Motion parameters are determined by solving face contact 
        constraint equations simultaneously using the singular value
        decomposition method.
        In order to maintain the relationship among motion parameters
        of previous operations, we define operation dependency lists
        (ODL), symbolic lists of homogeneous transformations to 
        represent operations.
        An ODL is calculated for each assembly operation, and is
        attached to each object.
        By using OLDs instead of object configurations, we can apply
        the same method to obtain correct motion parameters for former
        operations.
        We implement this method in the APO system, apply the method to
        several assembly examples, and verify the effectiveness of the
        method. 			 
        
        
Number: CMU-CS-91-168
Bibtype: TechReport
Month: Aug
Author: Takashi Suehiro
        Katsushi Ikeuchi		
Title: Towards an Assembly Plan from Observation: 
        Fine localization based on face contact constraints
Year: 1991
Address: Pittsburgh, PA
Super: @CMUTR