Specifications and Controls
Sonar sensitivity adjustment controls are accessible directly. For the front sonar, for
instance, locate a hole near the front underside of the array through which you can see
the cap of the sonar-gain adjustment potentiometer. Using a small 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
a heavy shag carpet, for
example. If the sonar are too sensitive, they will “see” the carpet immediately ahead of
the robot as an obstacle.
Increase the sensitivity of the sonar by turning the gain-adjustment screw clockwise,
making them more likely to see small objects or objects at a greater distance. For
instance, increase the gain if you are operating in a relatively quiet and open
environment with a smooth floor surface.
P
ROTECTIVE
IR
S
, B
UMPERS
,
AND
E
MERGENCY
STOP
Performance PeopleBot has two types of integrated IRs: fixed-range and breakbeam.
The robot’s fixed-range sensors are very reliable, diffuse-IR detectors mounted to the front
of the robot on each side and which detect obstacles, particularly tabletops or rope
barriers, that otherwise aren’t detected by the sonar. The fixed-range IR detectors
respond to any surface except glass or other mirrored surfaces, and can detect objects
as thin as a human finger. They are oriented to trigger when an object is 28 cm (11.5
inches) or nearer to the front of the robot and 3.75 cm (1.5 inches) at the height of the
lower deck.
Two breakbeam IR sensors, one on each side 3.75 cm (1.5 inches) forward of the left and
right column struts and between the top and lower decks of the robot, sense objects
which intrude into the robot’s profile, but which may not be otherwise detected by the
sonar or fixed-range IR sensors.
Figure 9. Bumper segments and
corresponding STALL value bit assignments
Bump rings fore and aft also provide
contact sensing for when other sensing
has failed to detect an obstacle. The
rings are segmented for contact
positioning.
Electronically and programmatically,
Performance PeopleBot’s IRs and
bumpers trigger digital events which
are reflected in the
STALL
and
DIGIN
values of the standard server-
information packet that AROS
automatically sends to a connected
client. Your client also may request a
special
IOpac
server information
packet that contains additional, more-
detailed bumper, stall, IR , and other
I/O related information.
AROS itself also monitors and responds to protection triggers. For example, AROS’
bump_stall
server triggers a stall in the robot whenever one or more bumper segments
get triggered while the robot is moving in the same direction (front forward or rear
reverse). Please consult the
Appendix A
for interface details and the chapters on AROS,
particularly the section which describes the contents of the
IOpac
server information
packet, later in this manual for configuration and programming details.
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