Analysis of drivable area and magnetic force in quadrupole electromagnetic actuation system with movable cores

Recently, significant attention has been paid to the development of electromagnetically actuated microrobots. Various types of electromagnetic actuation (EMA) systems have been proposed and put into practice. Owing to their limited workspace and driving force, the previous EMA systems were used restrictively in microrobots of specific sizes. Arguably, more research should be conducted on driving microrobots of various sizes using a single EMA system. In this study, a novel quadrupole EMA system with movable magnetic cores is proposed for driving microrobots of various sizes. Sharp magnetic cores and a closed magnetic circuit method are introduced to generate a magnetic field of high intensity and gradient with a small current. In addition, an analytical definition of the drivable area (DA) is presented in which a microrobot can move to the desired direction. The DA is estimated using a finite element method (FEM) and is verified via experimental results. The effectiveness of the proposed EMA system is verified by analyzing the changes in DA and magnetic force according to variations in the positions of the magnetic core. The results imply that driving microrobots of various sizes is possible. Moreover, it is shown that an EMA system with movable cores could be manipulated more efficiently than those with fixed cores.