Mathematica and BattleBots
Bringing Aggression, Determination,
and Mechanical Engineering to a Living Room near You
Looking for action with brains-over-brawn appeal? William
McHargue, a freelance physicist and long-time Mathematica user, is one
of many who find this combination in BattleBots, the new fighting-robot craze.
"With BattleBots, one can be aggressive and yet nobody gets hurt," says
McHargue. Recently, McHargue was featured in Mechanical Engineering
magazine for work on Tesla's Tornado, his BattleBot.
have hit the mainstream, thanks to their popular television series,
which is currently in its fifth season. More than just a TV show, BattleBots Inc. holds
the best-known fighting-robot tournament in the United States. Fans can find a
wide array of BattleBots merchandise including figurines, books, magazines,
video games, and clothing. The tournaments provide a forum in which builders
exhibit their ingenuity and expertise. BattleBots also challenges fans to join the
builder subculture with online tips and guidelines for creating BattleBots of
their very own.
Many BattleBot builders work in teams of three or more, but McHargue chose to
design and construct Tesla's Tornado on his own. Degrees in physics, electrical
engineering, and computer science made him particularly well equipped to
undertake the entire robot-building process. Although Telsa's Tornado hasn't yet
been featured on television, McHargue did rack up wins in his first season when
the BattleBot delivered knockout blows to its opponents.
In the BattleBox, Tesla's Tornado is a 117.9-pound block of spinning, smashing
steel. This BattleBot is so effective at wreaking mass destruction that testing
the robot outside of the reinforced bulletproof BattleBox is impossible. That's
why McHargue turned to Mathematica to model the efficiency of his
creation before he even began construction.
modeled Tesla's performance with Mathematica using
masses predicted by Cobalt, a solid-modeling program. "Mathematica
was employed to help predict the basic performance of the finished robot,"
McHargue says. Then, as McHargue finished crafting each component, he
incorporated the actual masses into the Mathematica model. Now, when
McHargue wants to make changes to his BattleBot, all he has to do is to plug the
new data into his existing Mathematica model.
McHargue's design philosophy is "to make a fighting robot as simple as possible,
yet still effective in combat." Tesla's Tornado, a competitor in the
60-to-120-pound middleweight division, appears rugged but harmless when sitting still.
Instead of elaborate contraptions such as the hammers, saws, and axes used by
other competitors, Tesla's secret weapon is its rotational inertia. To ensure
Tesla's effectiveness, McHargue graphed its rotational speed versus time from
start-up with Mathematica. "I needed to know ahead of time whether it
could spin up in a short enough time frame to defend itself," he says.
McHargue eliminated the turntable used in most "horizontal spinner" bots and
instead made the whole body the spinner. This puts Tesla's full weight behind its
spin, and at speeds surpassing 600 rpm, it can inflict some serious damage. At
full speed, Tesla's Tornado can exert a 28-millisecond impulse of nearly three tons
when its bot cutters strike a 120-pound opponent. "It is this kind of high, if only
short-lived, force that can break things," says McHargue.
In order to implement his innovative "chassis is weapon" design, McHargue
engineered the two powered wheels to perform multiple functions. First, they
spin in opposite directions with substantial torque to ensure that the bot will
accelerate to at least 200 rpm in three seconds, the amount of time it usually
takes opponents to cross the ring and attack. Then, to move around the ring,
each wheel brakes at specific intervals in the spin. When a wheel is braked, it
acts as a pivot point, resulting in bursts of carefully directed momentum, which
cause the bot to translate (move laterally) as directed by remote control. Since
Tesla's wheels are continuously running at high speeds, it can function only on
surfaces as smooth as the BattleBox floor without rapidly wearing out the
Adding to the experimental nature of his design, McHargue's control scheme is
also unique. He has created the only BattleBot that is controlled by infrared
light. Using light instead of radio waves provides a reference for the braking
that allows Tesla to translate. Converting the light source to a laser is on the
drawing board for his next competition. BattleBots safety regulations required
him to perform an analysis to prove that the laser would not harm anyone
viewing the fight. McHargue performed the calculations for this analysis and
typeset the report using Mathematica.
"The quality and robustness of the Mathematica system, the fact that
Wolfram has never stopped supporting Macintosh (my platform of choice since
1984), and the publication quality of its PostScript output are but a few
reasons I first turn to Mathematica when considering problems of a
general scientific or engineering nature," says McHargue. He also enjoys the
ability to carry units throughout all of his calculations. This helps guard against
accidentally overestimating Tesla's performance. McHargue notes that although
he could have done these calculations with other software tools, the notebook
environment's ability to use full symbolic expressions in actual equations and to
mix plots right in with everything else "just makes Mathematica a better
BattleBots airs on Saturdays at 8 p.m. Eastern Standard Time on Comedy
Central. For more information on BattleBots, check out the BattleBots.com