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rotational velocities with very high deceleration and remains stopped until it receives a subsequent
translation or rotation velocity command from the client.
Position Integration
Pioneer platforms track their position and orientation based on wheel motion sensed by encoder readings
and from the integrated gyroscope.
On start-up, the robot position is initialized to (X=0mm,
Y=0mm, θ=0°), pointing along the positive X-axis at 0 degrees.
As the robot moves, the position is updated with reference to
this initial coordinate frame, and the latest calculated position
estimate is reported in the standard SIP data packet (see
below) as XPos, YPos and Theta. X and Y coordinates are
provided in millimeters. θ varies between -179 to 180 degrees.
ARIA uses these position estimates to update its own stored
position, which may optionally have transformations
automatically applied to place the robot in any coordinate
system, or to make corrections.
Be aware that registration between external and internal coordinates deteriorates rapidly with movement
due to gearbox play, movement in robot suspension, wheel imbalance, wheel slip, accumulated small
errors in encoder sensing, and many other real-world factors. You can rely on the dead-reckoning ability
of the robot for a short range—on the order of several meters and one or two revolutions, depending on
the surface. (ARNL addresses this problem by using additional sensing and sophisticated localization
algorithms to correct the position of the robot with respect to features within a known and mapped
environment.)
You may translate and rotate the robot into a new coordinate system in ARIA using the
ArRobot::moveTo()
function. All subsequent position updates received by ARIA from the robot will
then continue to use that coordinate system to reflect movement of the robot.
Device Interfaces
The robot controller and and other devices are connected to the embedded computer via serial
connections through which commands can be sent and data received. These serial connections use
USB interfaces of the onboard computer (via FTDI USB-serial adapters).
ARIA has been preconfigured on the Pioneer LX embedded computer to connect to the robot controller
via the correct interface and using the correct baud rate as shown in the table below. On Linux, the
/etc/Aria.args
file contains the following default connection options:
-robotPort /dev/ttyUSB0 -robotBaud 57600
ARIAARGS
On Windows, the
options:
-robotPort COM3 -robotBaud 57600
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System environment variable contains the following default connection
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