The execution of automatically generated assembly plans by robots is one of the key technologies of modern and flexible manufacturing. During the execution of assembly sequences the robot comes into contact with the environment. Since there are positional and geometrical uncertainties from object representation, robot motion, and sensor information, compliance is used typically to prevent excessive contact forces. The contact forces and the resulting torques provide information about the contact geometry which is used to guide the assembly operation. We present a fast algorithm to identify assembly process states considering static friction under uniform gravity. This identification of assembly process states enables a robot to select and modify its motion strategies adequately according to the state. We give a symbolic representation of contact states and analyze the static properties of assemblies at each contact state by using the theory of polyhedral convex cones.

The execution of generated assembly plans by robots is one of the key technologies of modern and flexible manufacturing. During the execution of assembly sequences the robot comes into contact with environment. Since there are positional and geometrical uncertainties from object representation, robot motion, and sensory information, compliance is used typically to prevent excessive contact forces. These contact forces provide information about the contact geometry which is used to guide the assembly operation. In this paper we present an algorithm to classify and recognize contact states between subassemblies. We analyze the local depart space (LDS) given by the assembly planning system for the calculation, classification, and recognition of the contact states. The LDS describes the direction of motion for the separation of subassemblies involved in the assembly sequence. We calculate valid configurations of the active subassembly in an uncertainty region and use the theory of polyhedral convex cones for the recognition of contact states. Therefore, force-torque sensor information acquired in the assembly process is interpreted using state classifiers which are formulated by polyhedral convex cones.