From 66016e3d1b14d9270ccbf0144af894268ea53b11 Mon Sep 17 00:00:00 2001 From: Mike McCauley Date: Fri, 7 Mar 2014 08:14:39 +1000 Subject: [PATCH] AntennaTracker: initial documentation --- Tools/AntennaTracker/AntennaTracker.txt | 168 ++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 Tools/AntennaTracker/AntennaTracker.txt diff --git a/Tools/AntennaTracker/AntennaTracker.txt b/Tools/AntennaTracker/AntennaTracker.txt new file mode 100644 index 0000000000..24eff8ef0f --- /dev/null +++ b/Tools/AntennaTracker/AntennaTracker.txt @@ -0,0 +1,168 @@ +AntennaTracker + +Mike McCauley +2014-03-05 + +This is the ardupilot AntennaTracker + +This software, combined with appropriate hardware, can be used to cause a +high-gain antenna to track a mavlink equipped air or ground vehicle in real +time, providing higher quality radio links over longer distances than a +stationary or omnidirectional antenna. + +AntennaTracker can be a stationary installation on the ground, or can be +mobile, mounted on a vehicle, and moving at the same time as the vehicle it is +tracking, such as on a pursuit vehicle etc. + +Antenna Tracker Hardware + +The software works with: + +- Alt-Azimuth mounted antenna, equipped with 2 servos: one for Azimuth (also +called bearing or yaw) -180 to 180 degreees and one for Altitude (also +called elevation, or pitch) -90 degrees (straight down) to 90 degrees +(straight up). + +- Ardupilot compatible processor such as +-- Flymaple +-- others tested? +and with a radio or wired link to a source of mavlink messages with the +tracked vehicle's position data. + +A suitable power supply is also needed, possibly battery powered. In the case +of Flymaple, the onboard 5V regulator is not able to drive large servos +without causing large amounts of electrical noise in the processor, so you +would probably need an external 5V regulated supply + +Theory of Operation + +AntennaTracker receives real-time GPS position reports from the vehicle being +tracked (in the form of GLOBAL_POSITION_INT messages sent by mavlink radio +connection or possibly by hardwired serial connection). AntennaTracker also +knows it own current position. Based on these 2 sets of coordinates, it +calculates the magnetic bearing and elevation to the vehicle. It then moves +the tracker servos until the antenna (and the AntennaTracker processor) are +aligned with the desired bearing and elevation. At this stage the antenna is +pointed straight at the tracked vehicle. As the vehicle (and possibly the +antenna mount itself) move around, the servos are continually move to track +the vehicle. + +AntennaTracker currently only supports closed loop feedback to position the +antenna. This requires that AntennaTracker processor (including +accelerometers and compass) be mounted on the moving part of the antenna +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? + +- If the tracker is equipped with a GPS and it has 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 +recent good GPS fix is used. + +- If there is no good GPS fix since startup (either because there is no GPS +equipped or because the GPS has not yet got a fix), the most resently set HOME +location is used. + +- If no HOME location has ever been set in the tracker, 0.0 Latitude, 0.0 +Longitude, 0 Altitude are used (which is probably not very helpful) + +How does AntennaTracker get GLOBAL_POSITION_INT messages from the tracked +vehicle? + + + +Mounting + +The AntennaTracker processor must be mounted on the moving (ie the rotating, +tilting) part of the antenna tracker hardware. Just how you do this will +depend on your exact hardware, but if the processor is mounted in anything +other than the default orientation (ie with the processor default 'forward' +direction pointing in the direction the antenna points, you will have to +configure AHRS_ORIENTATION in the AntennaTracker configuration to suit your +mechanical mounting arrangements. + +In my case, I used a Flymaple with AHRS_ORIENTATION set to 1 (Yaw45). The +Flymaple was mounted on the antenna tracker with component side up and the +green pin headers horizontal and perpendicular to the antenna beam (See +pictures???). + +Configuration + +It is vitally important that your AntennaTracker be properly configured for the +mounting, servos and other hardware in your tracker. Unless you do this IT +WILL PROBABLY NOT WORK AS EXPECTED. CAUTION: It might even oscillate or flap +around. It might even damage itself. + +AntennaTracker (like other ardupilot software such as ArduPlane, APMRover2 +etc) has configuration values that control and tailor its operation, and which +are stored in EEPROM on the processor. The configuration is restored from +EEPROM every time the processsor starts. + +You can use MissionPlanner, mavproxy or apm_planner or other mavlink compatible +software to check and change the configuration of your AntennaTracker. + +You will almost certainly have to change the following configuration items to +suit, and possibly others besides: + +AHRS_ORIENTATION +RC1_MIN +RC1_MAX +RC1_REV +RC2_MIN +RC2_MAX +RC2_REV +PITCH2SRV_P +PITCH2SRV_I +PITCH2SRV_D +YAW2SRV_P +YAW2SRV_I +YAW2SRV_D + +(more info here about how to find the right values) + +You can find the complete set of configuration items I used for my Flymaple +tracker mounted on an Eagle Tree tracker WHERE????? + +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. + +You can do this by connecting to the AntennaTracker with mavproxy and issuing +these commands: + +disarm + - manually move the antenna so the antenna is level and pointing at 0 degrees elevation + i.e. at the horizon +level + - wait a minute without disturbing the antenna position +arm throttle + - this rearms the servos, allowing the antenna to move + +Operation + + + +How to set the HOME location + +If your AntennaTracker is not equipped with a GPS, you can still use it to +track vehicles. First you will have to tell AntennaTracker where it is on the +ground by setting its HOME position. + +Connect to AntennaTracker with mavproxy + +module load map + - the map will appear. + - Zoom and drag the map until you can see the location where + your AntennaTracker is located + - Click the mouse on the location of the antenna +wp sethome + +AntennaTracker will now remember this as its HOME location whenever it is +started.