Discrete event systems approach to fixtureless peg-in-hole assembly

Assembly tasks are normally performed with one robot and fixtures. Fixtures reduce the flexibility of the system and increase the cost of assembly. This paper addresses assembly without fixtures using two-manipulator robot. An active method using force feedback is proposed for the peg-in-hole assembly in highly uncertain environment. Assembly states are described by extended contact relations. Qualitative models for event evolution are easily derived from the marking of the Petri net model. The states are recognized through identification of the events using two 6-DOF force and moment sensors. The proposed method is verified and evaluated through experiments with round peg-in-hole assembly.