Aligning threaded parts using a robot hand

Techniques for determining and correcting threaded part alignment using minimal force and angular position data are developed to augment currently limited techniques for aligning threaded parts. These new techniques ore based on backspinning a nut with respect to a bolt and measuring the force change that occurs when the bolt "drops" into the nut. Kinematic models that describe the relationship between threaded parts during backspinning are introduced and are used to show how angular alignment may be determined. The models indicate how to distinguish between the aligned and misaligned cases of a bolt and a nut connection by using axial force data only. In addition, by tracking the in-plane relative attitude of the bolt during spinning, data can be obtained on the direction of the angular misalignment which, in turn, is used to correct the misalignment. Results from experiments using a bolt held in a specialized fixture and a Stanford/JPL hand are presented.