Simultaneous control of multiple MEMS microrobots

Abstract

We present control algorithms that implement a novel planar microassembly scheme using groups of stress-engineered microrobots controlled through a single global control signal. The global control signal couples the motion of the devices, causing the system to be highly underactuated. Despite the high degree of underactuation, it is desirable that each robot be independently maneuverable. By exploiting differences in the designs and the resulting electromechanical interaction with the control signal, the behavior of the individual robots can be differentiated. We harness this differentiation by designing the control signal such that some devices remain confined in small circular orbits (limit cycles), while the non-orbiting robots perform work by making progress towards the goal. The control signal is designed to minimize the number of independent control voltage levels that are used for independent control, allowing us to maximize the number of simultaneously controllable devices. Our algorithms were tested on systems of fabricated untethered stress-engineered MEMS microrobots. The robots are 240-280 μm × 60 μm × 7-20 μm in size and are controlled in parallel (simultaneously) within the same operating environment. We demonstrated the feasibility of our control algorithms by accurately assembling 5 different types of planar microstructures. © 2009 Springer-Verlag.