Control for Micro-Assembly of Heterogeneous MEMS Microrobots through Common Control Signal

We present a new efficient control framework for controlling groups of heterogeneous stress-engineered MEMS microrobots for accomplishing the micro-assembly process. The objective is to maximize the number of controllable microrobots in the system while keeping the number of external global signals as low as possible (highly underactuated system). This work proposes a theoretical control strategy that could complete multiple-shapes microassembly from arbitrary initial configuration where all the control primitives can be accompanied with a constant number (O(1)) of control pulses of the power delivery waveform. We show that with the new control strategy not only we can have a highly underactuated system but also we will have a robust controllable system which could complete the microassembly started from arbitrary initial configuration. These control methods are sufficient to implement a system that is robust against disturbance. The main contributions of the proposed control strategy is that 1) it can accomplish the process of the microassembly from arbitrary initial configuration, 2) it can control a highly underactuated microrobotic-system which allows maximizing the number of simultaneously individually controllable robots, 3) the size of the programming waveform does not grow with population size (i.e. size of the control primitive is O(1), 4) it is robust against disturbance and finally, 5) the assembly can be efficiently nucleated with arbitrary number of seed shapes. We focus on microrobotic systems that can be modeled as nonholonomic unicycles. We validate the control policy with hardware experiments for implementing planar assembly using multiple robots with direct drive wheels. These results lay the foundation for developing new methods to control of a large number of MEMS microrobots.