Pas de Deux avec les Microrobots
(Video)
Bruce R. Donald^a,b,*, Christopher Levey^c, and Igor Paprotny^d,a
aDepartment of Computer Science, Duke University, Durham NC 27708
^bDepartment of Biochemistry, Duke University Medical Center, Durham NC 27708
^cThayer School of Engineering, Dartmouth College, Hanover NH 03755
^dDepartment of Computer Science, Dartmouth College, Hanover NH 03755
*Corresponding Author:
Bruce R. Donald
Department of Computer Science
Duke University
Department of Biochemistry
Duke University Medical Center



The Video:
AVI with Cinepac Radius 157 MB
AVI with Cinepac Radius - zipped 142 MB

More information and additional videos can be found in reference [1] below and here:
http://www.cs.duke.edu/donaldlab/Supplementary/jmems08/


This video may not be used for commercial or for-profit purposes.
It is copyrighted by the authors.

Description: Video captured through an optical microscope, showing simultaneous control and operation of two stress-engineered microrobots. The dimensions of our microrobots are 260 x 60 x 10 micrometers; each robot consists of an unthetered scratch-drive actuator that provides forward motion, and a steering-arm actuator that controls whether the robot moves in a straight line or turns.

Our stress-engineered microrobots are electrostatically powered via a global control signal transmitted to all the robots regardless of the their position and orientation within their operating environment. Hence, a single control and power-delivery signal must be used to simultaneously control all robots within the same operating environment, resulting in a highly underactuated system. Despite this high level of underactution we are able to achieve independent control of the individual microrobots by designing their steering-arms to respond to different voltage levels of the supplied control signal.

This example uses nested hysteresis gaps. A hysteresis gap is the difference between the snap-down and release voltages for a steering-arm actuator. Nested hysteresis gaps allow us to set the states of the steering-arms (up or down) to any configuration. As shown in this video, all four states of the two microrobot steering-arms are used to choreograph their motion.

A disadvantage of nested hysteresis gaps is that they are control-voltage bandwidth intensive, limiting the number of simultaneously-controllable devices. An alternative multi-microrobot control scheme that minimizes control-bandwidth is described in [1].

References:

[1] B. R. Donald, C. G. Levey and I. Paprotny. "Planar Microassembly by Parallel Actuation of MEMS Microrobots." Journal of Microelectromechanical Systems, 2008; 17(4): 789-808.