Dan S. Reznik
& John Canny
University of California, Berkeley
"prehensile" automated manipulation involves a robot end-effector
(gripper), an object, and a sequence of pick-and-place operations. Gripper
and robot-arm clutter (see left inset), sensing and control difficulties, and the serial nature
of pick-and-place operations, renders this approach inappropriate if several
parts need to be manipulated simultaneously in a (possibly small) workspace.
Current research in Distributed manipulation
addresses this question by considering gripperless, non-prehensile devices
containing a large number of simple actuators organized in array fashion.
Different actuators types including micro-cilia, resonators (see right inset), rollers,
air-nozzles, and electromagnetic elements are being studied. Karl Böhringer's
page on Micro
Actuator/Manipulation Systems contains good information on this area.
An important premise in distributed manipulation is that a large number of
simple actuators can be used to manipulate a small number of parts. In
combining this idea with Canny and Goldberg's
minimalism in robotics, we have looked at a complementary question:
Can a device with few degrees of actuation freedom be used to manipulate -- i.e., independently translate and rotate -- a
large number of parts in a planar workspace?
Vibrations-based Part Manipulation: Bowl Feeders
||An inspiration to this question is the
bowl feeder (left inset) which achieves part orientation with a single moving actuator (the bowl!).
A drawback to this device is its non-programmability, i.e., its manipulation function
is tied to the shape of its internal track. We are interested in a programmable device, i.e., one for which the manipulation
task can be flexibly specified in software. a note of caution: vibrations-based
manipulation also has its drawbacks...
Minimalist Part Feeding
Our research in this field has started with the simpler problem of minimalist
part feeding. We have studied a device made up of a single, horizontally-vibrating flat
plate. The plate is constrained to translate along a single dof, e.g., X. We
have shown that by introducing a simple pump-like asymmetry in the plate's
vibration, parts placed on its surface feed forward at constant speed, due to
the sliding frictional forces developed.
Minimalist Parallel Part Manipulation
friction-based part feeding idea has been subsequently refined to that of parallel part
manipulation. By that we mean simultaneously steering -- i.e., translating and rotating -- multiple parts along independent
trajectories, e.g., as prescribed by a high-level planar task such as part mating, sorting, and/or presentation.
Pictures of experimental prototypes are shown on the right.
Our main result has been to show that
a single horizontally-vibrating plate is sufficient for such a manipulation