Study on Three Dimensional Dual Peg-in-Hole in Robot Automatic Assembly

Abstract

The analyses of the physics of robot assembly tasks are important in developing a flexible assembly system. Assembly analyses involve force/moment analysis due to contacts and jamming analysis due to improper force/moment. Because the uncertainty of geometry and control, contact states exist during the assembly process. Xiao presented the notion of contact formation (CF) in terms of principal contacts (PCs) to characterize contact states, and defined contact states as CFconnected regions of contact configurations (Xiao, 1993). They also examined the neighboring relations between contact states and characterized the contact state space as a contact state graph. Xiao developed an algorithm that automatically generated a highlevel contact state graph and planned contact motions between two known adjacent contact states (Xiao, 2001). Force/moment analysis is an important element in robot assembly analyses. Lots of research has been done on single peg-in-hole. Simunivic analyzed a round peg insertion problem, and derived two dimensional single peg-in-hole jamming conditions (Simunivic, 1972). Whitney adopted Simunovic’s approach to determine the force analysis of the same problem (Whitney, 1982). He identified wedging and jamming conditions and recommended ways to avoid insertion failure. A compliant mechanism, RCC (RemoteCenter-Compliance) was designed for axisymmetric part insertions. Sturges and Laowattana analyzed the wedging condition in rectangular peg insertion and developed a Spatial Remote-Center-Compliance (SRCC) (Sturges, 1988, 1996, 1996). Non-axisymmetric part insertions can be performed. Tsaprounis focused on the determination of forces at contact points between a round peg and a hole (Tsaprounis, 1998). Considerable theories have also been studied over the past years that define two dimensional mating between double rigid cylindrical parts (Arai, 1997, McCarragher, 1995 and Sathirakul, 1998). Arai described error models and analyzed the search strategy of a two dimensional dual peg-in-hole (Arai, 1997). McCarragher modeled assembly as a discrete event dynamic system using Petri nets and developed a discrete event controller