Actuation of ferrobots in a plane for independent and swarm motion using a grid of electromagnets

Abstract

Abstract We demonstrate an experimental platform for independent planar actuation of multiple ferromagnetic robots on a plane by locally varying the magnetic field around them using a 2D grid of solenoids. The ferromagnets can be brought together and separated, moved together in a swarm, or independently navigated using local magnetic fields, allowing for complex maneuvers. To enable this, they require strong fields to actuate and involve complications in force calculations. Modelling the force on the ferromagnet, which has field-dependent magnetization, is addressed by Legendre polynomial expansion of the integrand in the field equation, leading to significantly decreased computational effort. The developed method is used to apply required currents in the electromagnets and thereby move the ferromagnets along required paths in closed-loop motion. The accuracy of the developed force estimation is validated using finite element analysis, and it matches with less than 4% error. Furthermore, an autobraking mechanism with an optimal braking strategy is devised to mitigate the undesired overshoot and oscillations of ferromagnets. Several maneuvers of swarm and independent motion are presented. As a demonstrative case study, multiple ferrobots are used to change the shape of a planar elastic band to form a shape-changing robot, which is made to mimic processes in single-cell organisms.