A Cylindrical Halbach Array Magnetic Actuation System for Longitudinal Robot Actuation Across 2D Workplane

Magnetic actuation has been widely investigated for miniature robot control due to its wireless control capability. As a permanent magnetic (PM) actuation system, the Halbach array can provide strong and controllable magnetic fields with large motion workspace. However, existing cylindrical Halbach array systems can only generate axial force along its central axis and require the workspace (i.e., patient anatomy) to be manipulated inside the system for any useful robot manipulation, severely limiting their application for robotic surgery. In this work, we introduce a cylindrical Halbach array actuation system capable of generating a magnetic field with longitudinal gradients across a 2-dimensional (2D) workplane instead of only along the central axis, effectively extending the longitudinal force actuation coverage from 1D to a 2D plane. This is achieved by optimizing the magnet sizes and roll angles of the Halbach rows arranged circumferentially around the system. Co-alignment between the field and gradient directions is also achieved through proper configuration of the magnet pitch angles along each Halbach row, resulting in tip-leading robot motion capability. A series of model-based simulations were performed during the optimization process and later verified experimentally. The actuation system was experimentally demonstrated to stably drive a 2 mm diameter magnetic robot longitudinally at different locations within the workplane and at different velocities. This represents a significant advancement towards deploying cylindrical Halbach array systems for robot manipulation in clinical cases.