Robust independent and simultaneous position control of multiple magnetic microrobots by sliding mode controller

Abstract

Recent development in technology and improvement of manufacturing tools have accelerated the use of microrobots (MRs) in numerous areas such as micro sensing and medical applications. The ability to control multiple MRs simultaneously and independently could lead to higher performance, and even make new applications possible. In this paper, we have proposed a system for simultaneous and independent control of the position of multiple MRs in a plane. The system consists of 2N permanent magnets (PMs) with a circular arrangement in the plane around the workspace and a pair of Helmholtz coil to control N MRs. PMs are rotated by servomotors, and the coil aligns the orientation of the MRs normal to the plane. A sliding mode controller, as a robust approach, is designed to eliminate the undesired effects of disturbances and uncertainties. For this purpose, at each step, the required force for each MR is calculated based on the proposed controller, and corresponding angles of the PMs are computed analytically. The simultaneous control of multiple MRs is illustrated by simulation, and the performance of the system is discussed. Also, the position control of three MRs with dimensions of 250 µm, and a maximum speed of 330 µm/s is experimentally demonstrated.