If you're willing to wait half a minute,
Dan Resnick's vibrating table will pass you a glass of champagne all by
The Universal Part Manipulator is a table outfitted with
flexible legs and four motors that gently vibrate to move objects around
the surface. An overhead camera allows a computer to keep track of what's
on the table and coordinate movements. The part manipulator's most
complicated task to date is sorting poker chips by color.
inspiration for this device was a computer's 'clean up desktop' button,
said Dan Resnick, a postdoctoral student at Berkeley.
Windows... if you have folders scattered all over the place you can hit a
button... and all the folders go neatly to grid points and get neatly
rearranged. What if you could build a device that [automatically
rearranges] objects in the physical world?" Resnick said.
table has pairs of motors attached to two consecutive sides. This
configuration allows it to move in three types of ways within the plane of
the table: font to back using the motors on one side of the table, side to
side using the motors on the consecutive side, and rotating when motors on
the same side of the table move in opposite directions. "The motion is
always horizontal, there's no up and down motion," said Resnick.
Resnick likens the vibrating motion to a foot massage machine. "If
you put your hand on the table you can feel... a very low amplitude
vibration," he said.
The table is made of an aluminum honeycomb
material used for airplane floors because it is light and sturdy. "You
want [it] to be light because there's a motor that is pushing the table
around -- the lighter the table the smaller your motor can be," Resnick
The researchers developed motion primitives, or algorithms to
control the motors. The basic movement moves objects forward one
centimeter per second. "It executes a vibration in one direction very
quickly and then comes back in the opposite direction a little slower,"
allowing the object to slip forward slightly, said Resnick. If the
vibration is fast enough, the objects appear to be moving forward
Currently, the table shuffles objects around fairly
slowly. If it is moving one object at a time, the object will move one
centimeter per second. If the table is actively moving more than one
object to different places on the table, each object will travel a
fraction of that centimeter per second. For instance, if the table is
trying to move three different poker chips to different places on the
table, each chip will move at one-third of a centimeter per second.
The slowdown happens for the same reason it takes a juggler more
time to go through a juggling cycle as the number of juggled objects
grows, said Resnick. "It would take a longer time for the juggler to cycle
back to bottle No. 1 -- the same thing here. It is a kind of juggling
motion... and as you add more objects the table spends more time juggling
all the objects at the same time," said Resnick.
The table can
move several objects at full speed if it groups them, however, and it can
move one object at full speed while keeping others in place.
was both a trick and a hard part to the project, said Resnick. The trick
was realizing that it was possible to move one object on a plane while
keeping others in the same place.
The motion primitive that
accomplishes this applies a motion waveform to the table centered on the
object to be moved. This vibration causes all objects on the table to
move, but at the end of each millisecond long movement only the one object
will inch forward, while the others will end up back where they began.
The difficult part of the project was integrating several
technologies, said Resnick, pointing out that computer science, mechanical
design and electronic design were all involved.
The work is
impressive, said Matt Mason, professor of computer science and robotics at
Carnegie Mellon University. "There have been a number of robotics
researchers working on what we call nonprehensile manipulation or
graspless manipulation... Reznik's work takes this idea to a very elegant
extreme by moving several objects at once, giving each object an
independent motion. His work combines an elegant use of planar kinematics
with a creatively engineered use of friction to provide the motive power."
The work neatly sidesteps the difficult robotics problem of
designing a general-purpose grasping hand, Mason said. "The hand is just a
flat table, which fits all parts," he said.
There are issues still
to be addressed, he added. For instance, the universal part manipulator
can't handle round objects, and is fairly slow. "It might make sense to
think about having more than one plate ... [or] to consider other ways of
exciting the plates, or using shapes other than flat plates," said Mason.
Resnick is currently working on speeding the movement of objects
on the table by about three times and allowing it to handle a wider
variety of objects like pliers, computer chips, CD cases, books, and wine
bottles. "We're manipulating full wine bottles right now. [They're] more
unstable objects to manipulate then a glass because the bottle itself is
taller," Resnick said.
Eventually, he plans to produce specific
demos of more interactive tables like a desk that straightens itself, or a
kitchen table that knows where the salt shaker belongs. "I would either be
competing with the table to move [objects] to a specific spot or be aided
by the table," said Resnick.
Other future possibilities include a
warehouse with a smart floor that organizes boxes, or an entertainment
application that moves people around.
The table project should
produce something practical within two years, said Resnick. "I think a
couple years is a good horizon for something commercial to pop out of this
research," he said.
Resnick is continuing to work on the vibrating
table as postdoctoral student at Berkeley, but is also employed by
Resnick's research colleague is John Canny of Berkeley.
They have submitted a technical paper titled "C'mon Part, Do the Local
Motion," to the IEEE Conference on Robotics and Automation scheduled for
Seoul in May, 2001. The research was funded by the National Science
Timeline: 2 years
Story Type: News
Elements: Photo 1, Photo 2; Technical paper "C'mon Part, Do the
Local Motion," submitted to the IEEE Conference on Robotics and Automation
scheduled for Seoul in May, 2001; Technical paper "Building a Universal
Part Manipulator," IEEE Conference on Robotics and Automation in May, 1999
in Detroit; Resnick's demos www.cs.berkeley.edu/~dreznik/UPM2000/experiments.htm