Pioneer 2 - Manual (Page 17)

Pioneer Mobile Robots
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The sonar firing rate is 25 Hz (40 milliseconds per sonar per array) and sensitivity ranges from ten cm (six
inches) to more than five meters (16 feet). (Objects closer than ten cm are not detected.) You may control
the sonar’s firing pattern through software; the default is left-to-right in sequence for the forward array
(Figure 3-3) and right-to-left on the rear. One sonar from each array "ping" simultaneously.
The driver electronics for the forward and rear sonar sensor arrays each are calibrated at the factory.
However, you may adjust their sensitivity and range to accommodate differing Pioneer 2 operating
environments. The sonar gain control is on the underside of the sonar driver board, which is attached to the
floor of each sonar module.
Both banks’ sensitivity adjusment controls are accessible directly, although you will need to remove the P2
Gripper to access the front sonar, if you have that accessory attached. For the font sonar, for instance, from
the underside, locate a hole near the front of the sonar module through which you can see the cap of the
sonar-gain adjustment potentiometer. Using a flat-blade screwdriver, turn the gain control counterclockwise
to make the sonar less sensitive to external noise and false echoes.
Low sonar-gain settings reduce the robot’s ability to see small objects. Under some circumstances, that is
desirable. For instance, attenuate the sonar if you are operating in a noisy environment or on uneven or
highly reflective floor
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a heavy shag carpet, for example. If the sonars are too sensitive, they will “see” the
carpet immediately ahead of the robot as an obstacle.
Increase the sensitivity of the sonar array by turning the gain-adjustment screw clockwise, making the
sonar more likely to see small objects or objects at a greater distance. For instance, increase the sonar gain
if you are operating in a relatively quiet and open environment with a smooth floor surface.
Batteries and Power
The Pioneer 2 CE has a single, twelve-volt, direct-current, seven ampere-hour (84 watt-hour) sealed
lead/acid battery which supplies ample power for its drives, electronics, and accessories. Typical
intermittent operation of the motors gives six or more hours of Pioneer 2-CE use.
The Pioneer 2 DX and AT models may contain up to three, hot-swappable, seven ampere-hour, 12 VDC
sealed lead/acid batteries (total of 252 watt-hours), accessible though a hinged and latched back door.
Similar to the CE model, the battery life of the Pioneer 2 DX and AT, of course, depends on the
configuration of accessories and motor activity. Pioneer 2-AT charge life typically ranges from four
to eight hours. Pioneer 2-DX can run for more than a day.
If you don’t use the motors, Pioneer 2’s native electronics will run for several days on a single battery
charge.
Balance the batteries in your Pioneer 2.
IMPORTANT: Batteries have a significant impact on the balance and operation of your robot. For the
Pioneer 2-DX and 2-AT, under most conditions, we recommend operating with three batteries. Otherwise,
a single battery should be mounted in the center, or two batteries inserted on each side of the battery
container.
Typical recharge time using the recommended accessory recharger varies according to the battery’s
discharge state; it is roughly equal to three hours per volt. The optional Charge Cube allows simultaneous
recharge of three swappable batteries outside the robot.
With the optional high-speed Charger, recharge time is greatly reduced, but caare must be taken not to
overcharge and thereby damage batteries.
Electronics
The Pioneer 2’s standard electronics reside on three main boards: The microcontroller is mounted under the
Console Deck; a power / motor controller board is mounted to the battery box inside the robot; and a sonar
controller (one for each array) is mounted in the base of the sonar array.