Institute of Industrial Technology
bears little resemblance to the Hubo
bipedal humanoid developed by
KAIST. SeRoPi uses a far more stable
wheeled mobile base than Hubo and
Asimo’s bipedal structure. SeRoPi’s
wheels allow it to move about at
a fairly fast 4. 5 mph — a fast walk
for humans.
What distinguishes SeRoPi from
the others is its dexterous arms and
‘hands’ that allow it to reach down to
the floor to pick up objects. Using
dual stereoscopic camera eyes to
recognize objects, SeRoPi can use
both hands to manipulate these
objects using computer vision.
The 132 pound, 50 inch tall
robot maneuvers itself around on
two differentially-driven wheels
with a passive castor wheel for
balance.
FIGURE 8.
FIGURE 9.
The Robotis
Dynamixel Actuators
Robotis Bioloid Dynamixel servos
are different from all the other
model-aircraft types of servos because
of their onboard intelligence. In fact,
they’re referred to as actuators
instead of servos.
The basic AX- 12 Dynamixel
actuators (see Figure 10) have the
usual motor and associated geartrain
that we are all familiar with, but the
similarity ends there. Each AX- 12
FIGURE 10.
actuator has its own serial ID over a
‘Robotis TTL multi-drop digital packet
communications network’ and
because of this, a single set of three
wires — data, 9.6V VDC, and ground
— runs to all actuators in series. Or
they can be daisy chained together
as shown in Figures 11A and 11B
(courtesy of CrustCrawler).
There are two identical Molex
type connectors on the sides to allow
each successive actuator to be
connected with a jumper cable.
Typical PWM model aircraft servos
usually require three leads to each
individual servo, or at least an
individual 1.0-2.0 ms PWM signal
lead to each, and shared power and
ground leads.
Digital packet communication is
possible with all Dynamixel actuators
to control direction, speed, and
torque with actual feedback of these
parameters and — depending on
the model — outputs of internal
temperature, voltage, light, and sound
detection. The individual user manuals
are very well written. The higher-end
models — DX-117, EX-106, RX- 10,
RX- 28, and RX- 64 — use RS-485
network communication and have
metal gears.
The Dynamixel AX-S1 smart
sensor module integrates a three-directional infrared distance sensor, an
infrared remote control receiver, a
sound sensor, a light sensor, and a
buzzer, as well as the network
interface to communicate with the
actuators and controller. It can also
detect small internal temperature
changes, the system’s voltage, and
convey all readings into a range of
1,024 increments at up to 1 Mbps.
It utilizes the same daisy chain
interconnections as the series
of actuators.
As with the AX- 12, the
recommended operating voltage
for the AX-S1 is 9. 6 volts; not the
4. 8 to 6 volts with model aircraft
servos. The sensor module shown in
Figure 12 looks a lot like the AX- 12
and is mounted in a similar manner,
but the round flange is just a
mounting area, not a rotating disc.
The Robotis CM- 5 main controller
is based on the popular Atmel
ATMega 128 (128K of Flash memory)
running at 17 MHz. Also configured
for 9. 6 VDC, it can communicate with
the AX series of Dynamixels, their
two-axis gyro module, the AX-S1, the
Zigbee ZIG-100 standard, RS-232 or
RS-485 serial, and by six command
buttons on the panel. The controller
also has an LCD display for data
display and control. There is a
stand-alone CM-2+ evaluation
board with the same Atmel controller
and similar functions that is fully
compatible with the Bioloid
components for dedicated control
systems.
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