Modelling planar assembly tasks: representation and recognition

The assembly plan from observation (APO) system observes a human operator perform an assembly task, analyzes the observations, models the task, and generates the programs for the robot to perform the same task. The task model of the observed task is defined as a sequence of contact states of the part being assembled and the motion which causes the transition between the states. The freedom of the assembled part can be represented as a polyhedral convex cone (PCC) in screw space, which can belong to one of a finite number of distinct contact states. These contact states correspond to topologically distinct intersections of PCCs with a linear subspace T in screw space. Any observed assembly task can be represented as a finite sequence of critical contact states and the motion between them. The abstract task model is used to program the robot to execute the observed assembly task. We illustrate the application of the theory by implementing the APO system for assemblies in a plane