Peg-in-hole under state uncertainties via a passive wrist joint with push-activate-rotation function

This study presents a novel passive wrist joint with push-activate-rotation (PAR) functionality for a peg-in-hole assembly and a strategy utilizing the passivity and inherent functionality of the wrist. The PAR function involves rotation around a vertical axis, automatically activated by pushing the wrist in the vertical direction. The novel features of the approach are that 1)hardware based passive compliance absorbs uncertainties of the states for the peg, 2) no active rotational joints are required for the manipulator part, 3) F/T sensors are not used; instead, an IMU sensor is, and 4) multiple shapes for the peg or hole are available e.g., rectangular, circular, hexagonal, and triangular prisms. The validity of the approach is shown via several experiments.