Programmable Force Fields
Sensorless Positioning, Orienting, and Sorting (1992-1997)
Karl F. Böhringer, Bruce R. Donald (Cornell)
Increased miniaturization of mass-produced products such as disk drives,
displays, and sensors will require fundamental innovations in design and
parts handling. Many of the components in these products will be integrated
circuits and MEMS (Micro Electro Mechanical Systems) fabricated with massively
parallel wafer processing technology. Conventional pick and place robotic
techniques are inadequate for the efficient assembly of these micron-scale
components. This new economy of scale poses a fundamental challenge for
design and assembly. We propose an entirely new methodology founded on recent
insights from sensorless and minimalist robotics: massively parallel manipulation.
|Sensorless manipulation with PFFs:
two different examples of two-step open-loop strategies (the yellow
arrow indicates the direction of the force in the specific region
of the force field).
Figure 1: Sorting
by Size: in the first step parts are centered, and in the second
step they are separated such that small parts go left, and large
parts go right.
Figure 2: Sensorless Orienting: after this two-step
strategy, the ratchet-shaped part always reaches the same orientation
(modulo 180° symmetry in the force field).
The idea is to move parts using planar forces and moments that require
a minimum of sensing and servoing. The shape of the field, as defined
by the magnitude and direction of force at each point, can be designed
to position, align, sort, and assemble arrays of small parts in parallel.
The key to our approach is the programmable force field (PFF), an abstraction
defined with piecewise continuous functions on the plane, that can be
locally integrated to model the motion of parts interacting with the plane.
In the past two years, the PIs have used variants of this abstraction
to model different methods for implementing forces, such as arrays of
microactuators and vibrations of a plate. This abstraction is also related
to the theory of vector and potential fields that are used to model fluid
dynamics and hold great promise for modelling electrostatic forces and
compliant motion due to contact with rigid obstacles.
Recently, a new class of manipulators has been developed at the micro-scale
based on MEMS technology (Micro Electro Mechanical Systems fabricated
from silicon). These devices are both massively parallel (thousands of
devices on a chip) and extremely fast (motion cycles measured in micro-seconds).
Applying traditional digital control techniques would require increasing
controller CPU speeds by 6 orders of magnitude. Instead we propose to
develop techniques to allow real-time control of MEMS manipulators with
present-day computational hardware.
- K. F. Böhringer, B. R. Donald, Lydia Kavraki, Florent Lamiraux,
"Part Orientation with One or Two Stable Equilibria Using Programmable
Vector Fields." IEEE Transactions on Robotics and Automation,
16(2):157-170, April 2000. Paper.
- K. F. Böhringer, B. R. Donald, N. C. MacDonald, "Programmable
Vector Fields for Distributed Manipulation, with Applications to MEMS
Actuator Arrays and Vibratory Parts Feeders." International Journal
of Robotics Research, 18(2):168-200, February 1999. Paper.
- K. F. Böhringer, B. R. Donald, N. C. MacDonald, G. T. A. Kovacs,
J. W. Suh, "Computational Methods for Design and Control of MEMS Micromanipulator
Arrays." IEEE Computational Science and Engineering, 4(1):17-29,
January-March 1997. Paper.
A complete list of our publications
(many of them available online) can be found here.
- NSF IRI-8802390, IRI-9000532, IRI-9201699, IRI-9530785, and CISE/CDA
98-05548 IRI-9896020, and by a Presidential Young Investigator award
to Bruce Donald, NSF/ARPA SGER IRI- 9403903
- AFOSR, the Mathematical Sciences Institute, Intel Corporation, and
AT&T Bell Laboratories
© Karl F. Böhringer, Department of Electrical Engineering, Box
352500, Seattle, WA 98195-2500, USA