Open-Loop Magnetic Actuation of Helical Robots using Position-Constrained Rotating Dipole Field

Abstract

Control of tetherless magnetically actuated helical robots using rotating dipole fields has a wide variety of medical applications. The most promising technique in manipulation of these robots involves a rotating permanent magnet controlled by a robotic manipulator. In this work, we study the open-loop response of helical robots (in viscous fluids characterized by low Reynolds numbers) in the presence of position constraints on the actuating rotating permanent magnet. We first derive a mapping between the space of the manipulator’s joints, the produced magnetic fields in three-dimensional space, and the translational and rotational velocities of the helical robot. Then, we constrain the 3D position of the rotating dipole field and predict the response of the helical robot by controlling its angular velocity using the constrained mapping. We demonstrate open-loop control and gravity compensation of the robot using the angular velocities of the actuating permanent magnet while enforcing constraints on the end-effector position.