Assembly tasks are ofien performed by one robot with some devices to hold parts, or fixtures. This type of assembly system has low flexibility in terms of the variety of parts and thd part- presentation the system can handle. This paper addresses assembly without fixtures using a two- arm robot. An active method by which a two-arm robot can assemble the peg and hole using force feedback was proposed previously. In this method, an assembly state is modeled as that of having a unique control command and the events between assembly states are modeled through qualitative reasoning. Based on the proposed active method, this paper defines three basic motions for assembly, constructs assembly sequence diagram using the definition of the states, events, and three basic motions, and implements the proposed method with a two-arm robot
system.
In order to accomplish the purpose, a two-arm robot system is constructed which consists of two 5-d.o.f. manipulators and two 6-d.o.f. force/torque sensors. Experiments with the fixtureless peg-in-hole assembly is presented to verify and evaluate the method.
