Name: Vbug 1.5 aka. "Walkman"
Designer: Mark W. Tilden
Build Date: Dec 15, 1993 - April 1,
- 4 x Escap MU915L gearboxes (151:1 gear
ratio) for each leg.
- 1 x Motorola Phone vibration motor
driving a brass "oven timer" mechanism.
- 3 chip analog controller using 4 Nv
"Microcore" in a 74HC14 plus 2 x 74ALS240s as motor drivers and
- All extra analog components salvaged
from Sony Professional Walkmans.
- 730grams (including rechargeable NICADs)
- 4.8v operation with over 2 hours of
runtime from a single charge.
- Could walk over any complex surface
equal to it's own resting height.
- Forward, backward, left-right turning and
- 5 multi-directional wire touch sensors
(4 corners and 1 forward) and two phototropic eyes for light following
- Nv "Necklass Function" processes could
fall into 3 distinct patterns allowing it to rest, walk, and "dig".
- Unusual ability to extract itself from
difficulty using unconstrained pivot limbs.
- Asymmetric control signals even mimicked
a form of "learning ability" due to motor-load variations affecting process
refractions in beneficial ways.
In Mark Tilden's first year as a physicist
at Los Alamos National Laboratory he took advantage of formal time to apply
his theories of minimalist biomorphic design, building a range of
experimental insectoid robot platforms for scientific study. Following a
New York Times interview in 1993 (covering Tilden's fame as organizer of the
BEAM Robot Games that year), the reporter mentioned that the Times had
dozens of broken Sony "Walkman Professionals" used to destruction, and
they'd be glad to send them along. About a dozen did show up which Tilden
carefully dissected and used in a variety of first-generation research
walkers. Walkman 1.5 was the most successful and certainly the most famous
of the twelve-robot line, many of which were built concurrently over a 2
Knowing his Nervous Network control theory
was robust enough to work anything, Tilden built his robots only from
discarded components and in non-uniform ways to prove the point, and Walkman
was no exception. The robot was built from a vast array of diverse
components from the famous "oven timer" gearbox, Motorola phone vibrating
motors, Walkman gearboxes and analog electronics, gold PCB test pins, and
parts from old laser-printer cartridges, even the PCB the circuit was built
on was scavenged from an 1980s Sun Microsystems video board. Indeed, there
was nothing in the robot (as in the entire VBug series) that was not second
hand. The entire robot was "wire-framed", with solder as the primary
structural element holding it together. Walkman and his brethren even
garnered a Guinness World Record for "World's Least Expensive Research
Robot" from 1997 to 2001.
standing on one of the extra walkmans donated by the reporters at the New
York Times. The first Walkmans donated were used to build the robot itself.
Despite appearances nothing on Walkman was
decorative -- sensors were all shaped to optimize object detection as the
asymmetric robot explored, gold video-cable pins were used for contacts to
optimize lifetime, even the aluminum backplate was used as a heat sink for
the 240 bus driver chips (pushed well beyond their ratings as both motor
drivers and multiplexers).
Walkman turned out to be the darling of
Tilden and Hasslachers international lecture circuit from 1994 to 1999,
showing how emergent competence could rise from simplicity (a stalwart of
the Artificial Life movement during that time). During a lecture at the MIT
Robotics Laboratory in 1995 the famous Marvin Minsky, after examining
Walkman, put it down and exclaimed "I don't know where you've hidden the
wireless modem link to the computer that's actually controlling this thing,
but I know it has to be in there somewhere." Despite a long emotionally
charged discussion afterwards, no opinions were changed despite experimental
evidence and repeated tests.
In 1997 Walkman was taken to Washington DC
for study and presentation by various science agencies to drum up funding
interest in Biomorphic Robotics -- a "new form" of robotics that appeared
capable but significantly less expensive than conventional methods. It was
during this time that Walkman was found missing after a prominent
presentation to congress having been lifted from a Capitol Hill exibition
table without a trace. Walkman was gone for over 15 months until the fall
of 1998 when it was returned to Tilden by a new DARPA Project manager who
had "found it" along with various other Tilden robots in an Arlington
Virginia government office. Several other robots were also returned that
had been delivered to diverse sponsors over the years (of the original
twelve VBug robots built, seven are still unaccounted for).
Walkman was very animated and quite
enigmatic to watch. It showed an incredible exploration competence despite
simplicity and even a demonstrable memory effect, being able to extract
itself from any leg trap again using the same method it would "find" after
only 30 seconds of flailing, and again almost immediately. Though there
was much study and papers written on Walkmans abilities, they were never
properly described or explained, and Walkman's abilities remain a mystery
until this day.
Vcc phase space sampled during 5000 steps.
Symbol lexicon layout showing topological simplicity.
Walkman 1.5 schematic showing the chips in the actual positions and their
exact wiring allocations. The bottom 4 resistors in the middle set the
tuning for the very asymmetric structure and took Tilden well over a day to