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In this work, we develop methods for controlling multiple untethered magnetic micro-robots (called Mag-μBots), with all dimensions under 1 mm, without the need for a specialized surface. We investigate sets of Mag-μBots that are geometrically and magnetically designed to respond uniquely to the same magnetic fields. The responses of geometrically dissimilar Mag-μBots with similar magnetization and a group of identically-fabricated Mag-μBots are investigated. By controlling the magnetic field waveforms, individual and subgroups of Mag-μBots are able to locomote in a parallel but dissimilar fashion. Specifically, the pulsing frequency of the imposed driving magnetic fields is used as a selection method among the Mag-μBots. This method for accomplishing motion discrimination is discussed, modeled, and tested. Independent global positioning of two and three robots is demonstrated in two-dimensional space. While individual Mag-μBot velocities can be as high as 7 mm/s, the effective velocities during multi robot control are found to be up to 2 mm/s. As this control method is accomplished without the use of a specialized surface, it has potential applications in areas such as micro-fluidic systems and bio-manipulation.