From 7116fdecde6ecc01a8e4d4d1686403da94a49d2d Mon Sep 17 00:00:00 2001 From: Mike McCauley Date: Thu, 27 Mar 2014 09:04:36 +1000 Subject: [PATCH] AntennaTracker: added documentation about compass calibration to AntennaTracker.txt --- Tools/AntennaTracker/AntennaTracker.txt | 57 +++++++++++++++++++++---- 1 file changed, 48 insertions(+), 9 deletions(-) diff --git a/Tools/AntennaTracker/AntennaTracker.txt b/Tools/AntennaTracker/AntennaTracker.txt index fa2adb6b17..7591e575fc 100644 --- a/Tools/AntennaTracker/AntennaTracker.txt +++ b/Tools/AntennaTracker/AntennaTracker.txt @@ -54,9 +54,9 @@ tracker hardware. The servos are moved until the yaw and pitch of the processor (and therfore of the antenna itself) matches the bearing and elevation to the tracked vehicle. -How does AntennaTracker know where it is? +How does AntennaTracker know where it is on the earth? -- If the tracker is equipped with a GPS and it has a good 3D fix, the most +- If the tracker is equipped with a GPS and it has had a good 3D fix, the most recent good GPS fix is used. - If the tracker is equipped with a GPS and it has lost its fix, the most @@ -72,7 +72,17 @@ Longitude, 0 Altitude are used (which is probably not very helpful) How does AntennaTracker get GLOBAL_POSITION_INT messages from the tracked vehicle? - +mavproxy, when it runs the tracker module, intercepts all GLOBAL_POSITION_INT +messages received from its master vehicle, and sends them to the tracker. It +knows how to connect to the tracker with the set port and set baudrate +commands, for example to connect by a USB-Serial radio, such as the 3DR Radio +on port /dev/ttyUSB0: + +(after starting mavproxy) +module load tracker +tracker set port /dev/ttyUSB0 +tracker set baudrate 57600 +tracker start Mounting @@ -127,13 +137,42 @@ available) You can find the complete set of configuration items I used for my Flymaple tracker mounted on an Eagle Tree tracker WHERE????? +Compass Calibration + +AntennaTracker uses its internal magnetic compass to determine where North is +and therefore where to point for each bearing to the target vehicle. (On other +ardupilot vehicles, the yaw is also calibrated by the current GPS track. This +is not possible for AntennaTracker, so the compass is the only possible source +for absolute bearing) + +The compass magnetometer is exquisitely sensitive to nearby magnetic fields from +wires, metal fittings, servos, radios etc. Therefore is it VITALLY ESSENTIAL that you +calibrate the compass. Further, it must be calibrated outdoors, while installed +in situ in the tracker, with all other equipment installed, fastened down and +ready to operate. + +Failure to calibrate correctly will result in the tracker pointing in the +wrong direction, or the azimuth/yaw and elevation/pitch drifting. + +Use Mission Planner to calibrate the tracker: +- Assemble the completed tracker, complete and ready to operate. +- Power up the tracker +- Connect to it with Mission Planner +- On Mission Planner->INITIAL SETUP->Compass, click on Live Calibration +- click on OK +- rotate the complete antenna tracker assembly around, in 3 dimensions, making sure to +rotate the tracker to every possible orientation in the 1 minute you have +available. DONT just move the yaw and pitch motors around. You will probably have to +pick the whole thing up. +- At the end of the minute, Mission Planner will update AntennaTrackers compass offsets. + Levelling -Since AntennaTracker uses its internal accelerometers to determine the current -elevation/pitch of the antenna, it is important to 'level' the AntennaTracker -before use so the accelerometers are calibrated. Failure to do this will -result in the antenna constantly pointing a bit high or a bit low compared to -the tracked vehicle. +Since AntennaTracker uses its internal accelerometers (amongst other things) +to determine the current elevation/pitch of the antenna, it is also important +to 'level' the AntennaTracker before use so the accelerometers are +calibrated. Failure to do this will result in the antenna constantly pointing +a bit high or a bit low compared to the tracked vehicle. You can do this by connecting to the AntennaTracker with mavproxy and issuing these commands: @@ -152,7 +191,7 @@ Operation After powering up AntennaTracker, it may take up to 1 minute while it automatially calibrates the compass before it points in the expected -direction. +direction. Moving the tracker around will speed up this process. How to set the HOME location