Single Force-Guided Precision Peg-in-Hole Search of Cylindrical Part with Small Length/Diameter Ratio

This paper presents an approach to deal with precise positioning for valve spool of precision solenoid valve in automatic assembly. The valve spool is the cylindrical part with length/diameter ratio less than 0.3 and the mating clearance is narrower. At present, its assembly process is positioning first and then inserting. Lacking real-time feedback about the contact state, the positioning accuracy of assembly is limited by the cumulative motion error of the operating mechanism. Therefore, to achieve this assembly, expensive precision operating equipment must be used. However, this paper proposes an approach of single force-guided peg-in-hole search to solve problems of accuracy and cost. Utilizing the adaptive deformation of the flexible manipulator and combining with the high-frequency one-axis force sensor, the approach creates a motion control algorithm based on the force decay during search phase. The experiments are tested with the mating parts which have diameter 20mm and radial clearance 6μm. The success ratio 94.2% validates the feasibility of the approach.