Portable Body-Attached Positioning Mechanism Toward Robotic Needle Intervention

This article presents a robotic needle positioning approach with a novel 4-DoF parallel positioner, two back-driveable 2-channel linear/rotational driver, and a machine-body interface. Being more compact and flexible, Ni-Ti alloy wire-based Bowden cable transmission is introduced to connect the positioner and the drivers. For this new mechanism, forward and inverse kinematics are derived, and the workspace is analyzed. The mechanism's maximum incidence angle is 45$^{\circ }$, and the stroke of the slider is 41 mm. The structural size of one positioner is $\varnothing$70 mm × 45 mm. The compact size and lightweight of the positioner make it readily mountable on the skull or attached to other parts of the body. We fabricated a 3D printed proof-of-concept prototype of the system and tested its performance. The open-loop positioning accuracy of the slider and rotor is within $\pm$1 mm and from $-0.8^{\circ }$ to 1.5$^{\circ }$, respectively. The trajectory tracking error of the system is within 1.71 mm. The stiffness of the positioner in the x- and y-directions can be calculated as 9.03 and 11.91 N/mm, respectively. Finally, an image-guided navigation framework based on electromagnetic tracking demonstrates the feasibility of the proposed system on a phantom study.