Realization of spatial compliant virtual fixture using eigenscrews.

Virtual fixture is kind of assistance mechanism to limit movement into restricted regions and/or guide movement along desired trajectories in human-machine interactive operation. The structure of geometric and dynamic constraints of reference tasks is analyzed using screw theory. End-effector and the reference frame are elastically coupled by virtual screw springs, which slides along the reference sequences. An allowable motion screw set is constructed, from which the desired spatial compliance and stiffness matrices are synthesized from an allowable motion screw set. The presented virtual fixture are implemented dynamic contour tracking experiment, the effects of control parameters on system performance are also analyzed. The proposed virtual fixtures unites rotation and translation motions, and filter out task-unrelated components from the manual input while augmenting task-related components.