Position-based magnetic field control for an electromagnetic actuated microrobot system

This paper proposes an electromagnetic actuation (EMA) system using two pairs of coils (4 coils) which can realize 2 degrees of freedom (DOF) motion (roll and translation motion) on a 2-dimensional (2-D) plane. Previously, for 2 DOF motion of a microrobot on a 2-D plane, two stationary pairs of Helmholtz coils and two stationary pairs of Maxwell coils (8 coils) were used. However, the proposed EMA system has only two stationary pairs of coils and carries out the same 2 DOF motion as that of a microrobot. Compared with the previous EMA system, the proposed EMA system has 18% smaller volume and 26.7% less power consumption for the same actuation of a microrobot in the same region of interest (ROI). For the control of the electromagnetic field in the EMA system, in general, it is assumed that the generated magnetic field in ROI is identical to the desired magnetic field at the center of ROI. However, the generated magnetic field at the edge of ROI differs somewhat to the desired magnetic field and the difference of the magnetic field can induce a microrobot positioning error. Therefore, to increase the positioning accuracy of the microrobot, the real-time position value of the microrobot is used to generate the desired magnetic field at each position. Through the proposed position based magnetic field control, the position error of the microrobot can be reduced to less than 0.33 mm. Finally, it was verified that the EMA microrobot can accurately move along desired paths by the position based magnetic field control. (C) 2013 Elsevier B.V. All rights reserved.