Planning and control for microassembly of structures composed of stress-engineered MEMS microrobots

Abstract

We present control strategies that implement planar microassembly using groups of stress-engineered MEMS microrobots (MicroStressBots) controlled through a single global control signal. The global control signal couples the motion of the devices, causing the system to be highly underactuated. In order for the robots to assemble into arbitrary planar shapes despite the high degree of underactuation, it is desirable that each robot be independently maneuverable (independently controllable). To achieve independent control, we fabricated robots that behave (move) differently from one another in response to the same global control signal. We harnessed this differentiation to develop assembly control strategies, where the assembly goal is a desired geometric shape that can be obtained by connecting the chassis of individual robots. We derived and experimentally tested assembly plans that command some of the robots to make progress toward the goal, while other robots are constrained to remain in small circular trajectories (closed-loop orbits) until it is their turn to move into the goal shape. Our control strategies were tested on systems of fabricated MicroStressBots. The robots are 240–280 μm × 60 μm × 7–20 μm in size and move simultaneously within a single operating environment. We demonstrated the feasibility of our control scheme by accurately assembling five different types of planar microstructures.

Feedback control of many magnetized: Tetrahymena pyriformis cells by exploiting phase inhomogeneity

“…A suitable Lyapunov function is the squared distance of the center of rotation, [x c,i , y c,i ] (5), from the origin: 1 V(t, x,y) = 7:J2 (xl,i(t) + yl/t)) (6) i=l We construct several control laws that stabilize the system with the proposed Lyapunov function. …”

“…In previous work [2], [3], we focused on micro/nanorobotic systems with control inputs (forward velocity and turning rate) applied to the local coordinate frame, such as electric potential-driven scratch-drive micro-robots [4]- [6] and some light-actuated, molecular nanocar species [7], [8]. These robots have bounded uncertainty in their velocity which scales both their forward velocity and their turning rate.…”

“…In [4]- [6] the authors designed robots with varying hys teresis levels so that some could orbit in place while others went straight. By cleverly interleaving primitives, they con structed shapes composed of multiple robots.…”

“…The cells start in a vertical line at {[10,5],[10,6],[10,7],[10,8]} mm and are steered to orbit goal positions in a horizontal line at {[-6,0], [-2,0], [2,0], [6,0]} mm. The magnetic field has frequency 15 rad/s, the a values are {5, 6, 7,8}, and the speeds v are {0.8,0.5,0.6,0.7} mm/s.…”

Automated real-time control of fluidic self-assembly of microparticles

“…For instance, Tolley described the directed fluidic assembly of micromachined, mechanically-locking tiles into irreversible multimeric structures [13]. Donald demonstrated the use of a single global control signal to drive microassembly of stress-engineered MEMS robots [14]. A magnetofluidic apparatus for the directed reconfiguration of sets of millimetric, water-floating magnetic modules was developed by Miyashita [15].…”