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6.3
Important aspects and hints
The single most important aspect for the system to work well is to have proper ultrasonic
coverage
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Each sensor has an ultrasonic beam of ~90 degrees. Outside of that range the emitting power and
sensitivity drops quite rapidly. From the left, right, or back sides of the ultrasonic sensor the signal is
received highly attenuated. Thus, it is crucially important to provide proper ultrasonic coverage for
the area where the robot will be moving
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Also it is very important to provide proper ultrasonic coverage to other stationary beacons when the
map is being formed
Mobile beacon (‘hedgehog” or “hedge”) is designed to be placed horizontally
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Mobile beacon has four horizontal and on vertical sensors each covering its own sector. Together
they cover 360 degrees horizontally and upper hemisphere. Lower hemisphere is highly attenuated,
so don’t expect ultrasonic coverage in that area
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It is advised to place the mobile beacon as high as possible on the robot, if stationary beacons are
above the mobile beacon, to minimize shadows from other objects, people, etc.
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Example of proper positioning of the mobile beacon:
https://youtu.be/PFgNPkLGCDk
- the beacon is
placed horizontally and above other objects that can produce shadow to the stationary beacons
Keep the radio signal’s strength under control
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RSSI (Dashboard => right menu) of any beacon must not be higher than -25dBm. Otherwise, the
system may malfunction (packets lost unnoticeable, etc.)
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It is recommended to keep the distance between beacons not less than 0.5-1m. Beacons can as
close to each other as you need so. If beacons are extremely close from each to each, just
disconnect antenna from the beacon. Monitor Received Signal Strength Indicator (RSSI). It must be
