each and every step of motion is an amazing tool, making
the creation of walking gaits and motions an infinitely more
precise and controlled process. Once motions are created,
they can be easily mapped to various inputs on the PS3
controller or (in the case of the pan/tilt assembly for aiming
the joysticks) can be used to directly control specific servos
for direct aiming.
Telepresence, Weapon, and
As discussed in a previous installment, one of the
requirements to compete in the Mech Warfare competition
is that each robot must carry a wireless video solution. The
“standard issue” most competitors are using is the Trendnet
IP-110W WiFi camera which can maintain 30 fps at
320x240 resolution in a very compact form factor. Given
that I had a larger bot, I went for a more robust solution
and implemented a wireless IP video encoder which is more
or less a WiFi video server. It allows the use of any standard
NTSC camera, so I took advantage of this and chose a high
resolution one: the Sony Ex-View CCD 38CSHRX.
The video encoder unit digitizes the video feed and
provides an IP address in which to pull the feed from; once
attached to my own mobile wireless network, it was a plug
and play solution that worked out rather well. Even at the
highest resolution, I was able to maintain a solid 30 frames.
Figure 3 shows the wireless IP video encoder and camera.
Now, while I could stop here, why not take the immersion
provided from telepresence to the next level?
I had reviewed numerous “video goggle” setups and
found most of them to be rather poor in quality and had
all but given up until I came across the personal cinema
system known as Headplay. This unit provides HD quality
video feed “projected” in front of your eyes through two
small LCD displays, with the option to adjust inter-pupillary
distance, as well as focus. With a VGA input, I could plug
the visor-mounted unit into my laptop and view the video
feed from the robot in full resolution right in front of my
eyes; kind of like sitting inside the robot. Figure 4 shows
50 SERVO 08.2009
the unit and supporting electronics.
The Airsoft guns used on Hagetaka were actually
purchased at a local Wal-Mart and chopped down to size.
Rather than break into the available I/O of the Gumstix
and interface an H-bridge to control the motors, I chose a
simpler (albeit more expensive) solution suggested to me by
Rob Farrell and used the internal controller of an RX- 10
servo to control the motor. This essentially turns each
Airsoft gun into a Dynamixel which, in turn, is easily
interfaced to the existing software and power system.
Furthermore, the LED onboard the Dynamixel control board
can be used with a small pFET circuit to drive a laser.
Powering Hagetaka is an 18.5V 5S 4,000 mAh LiPo
battery which sits inside the upper torso underneath the
electronics. At full capacity, the battery sits at 21V which is
ideal for the upper voltage range of the RX-64s. However, I
needed to drop this voltage down for the other components of the mech. First of all, the RX-28s would not be
happy running at that high of a voltage. Finding a voltage
regulator that was compact and yet robust enough to
handle two high torque servos took a bit of a search.
Luckily, Dimension Engineering was kind enough to grant
me a beta test of their upcoming AnyVolt3 variable DC-DC
converter which can take output 5V-30V at three amps
while taking in 3V-24V.
The unit itself was very compact, lightweight, and
cool running; making it a perfect fit on the rear side of my
RX- 28 pan servo. I also made use of a pair of DE-SWADJ3
25W step-down adjustable regulators from Dimension
Engineering to provide a stable 12V power supply for the
wireless camera system and onboard scoring board. From
there, a 5V regulator from Robotics Connection tied into
the 12V supply to provide a regulated power source for the
I have been writing this series of articles as I have been
building the final revision of Hagetaka which, unfortunately,
leaves their completion prone to disaster. During the crunch
to get Hagetaka combat ready in time for RoboGames, I
spent many sleepless nights burning the midnight oil. On
one such night, I fell victim to Murphy’s Law and ended up
creating some magic smoke which would ultimately put me
out of the running to compete in Mech Warfare this year.
I feel we always learn best from our own and other’s
mistakes, so I’ll share my failures in hopes of gaining your