Operation Manual

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6.3 Important aspects and hints
The single most important requirement for the system to work well is to have proper ultrasonic
coverage
- 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
- 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
- Mobile beacon has four horizontal and one vertical sensors each covering its own sector. Together
they cover 360 degrees horizontally and 180 degrees in the upper hemisphere. Lower hemisphere is
highly attenuated, so don’t expect ultrasonic coverage in that area
- It is advised to place the mobile beacon as high as possible on the robot, if stationary beacons are
above the mobile beacon. This minimizes shadows from other objects, people, etc.
- 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
- RSSI (Dashboard => right menu) of any beacon/modem must not be higher than -25dBm.
Otherwise, the system may malfunction (packets lost unnoticeable, etc.)
- It is recommended to keep the distance between modem and beacons not less than 0.5-1m.
Beacons can as close to each other as you need so. If beacon is extremely close to the modem, just
disconnect antenna from the beacon. Monitor Received Signal Strength Indicator (RSSI). It must be
in the range of -25…-70dBm. Lower than -70dBm will work too, but packet losses may start
occurring. The quality of radio connection very much depends on the external interference too,
because the used band is ISM (either 915MHz or 433MHz) and there are many systems co-existing.