This paper deals with precise insertion processing
(peg-in-hole task) for speeding up and increasing
flexibility of assembly process in factory automation. When
a gap between a peg and a hole is narrower than positioning
accuracy of robotic manipulator, it is impossible to succeed
the peg-in-hole task by conventional position control
methods. Moreover, in the case that a robotic hand holds a
deformable thin ring and put it around a shaft, the insertion
process becomes increasingly difficult because the gripping
force deforms the ring and the narrow gap is crushed.
We propose a novel mating technique based on passive
alignment principle (PAP) in order to solve the twin problems
of accuracy and deformation. The PAPmechanism can
correct the ring position in nanoorder and remove the ring
deformation. We derived the limitations of the PAP, which
are remaining position errors after the PAP applied, based
on Hertz stress. We also analyzed accuracy requirements
of industrial robotic manipulator for applying the PAP and
calculated allowance diagrams. We conducted 280 mating
and insertion experiments with four kinds of materials of
rings and shafts with three different insertion directions.
The success rate 97.8% validates our proposed PAP-based
mating algorithm.