Electromagnetic actuation system using stationary six-pair coils for three-dimensional wireless locomotive microrobot

Abstract

This paper develops a three-dimensional (3D) electromagnetic actuation system (EMA) for a magnetic microrobot locomotion in 3D space. The EMA system consists of stationary six-pair coils which include three pairs of Helmholtz coils and three pairs of Maxwell coils set in three orthogonal directions. The uniform magnetic field produced by Helmholtz coil and the uniform gradient magnetic field produced by Maxwell coil allow us to take advantage of those properties to establish the 3D EMA system which can produce controllable magnetic field in the 3D space by independently changing the current in each coil. Microrobot is subjected to magnetic force and magnetic torque under the external magnetic field. Simultaneously combining uniform magnetic field with uniform gradient magnetic field ensures that the magnetic force keeps constant to drive the microrobot wirelessly, and the microrobot overcomes the gravity and liquid resistance and achieves stable locomotion in the 3D region of interest (ROI). We establish the open-loop control algorithm for the gravity compensation of the 3D wireless locomotive microrobot. In the end, we validate the performance of the EMA system and the proposed control method by microrobot locomotion experiment in 3D liquid environment.