mirror of https://github.com/ArduPilot/ardupilot
AntennaTracker: initial documentation
This commit is contained in:
Mike McCauley
Andrew Tridgell
parent
b4a0c7db63
commit
66016e3d1b
|
|
@ -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?
|
||||
|
||||
<more here>
|
||||
|
||||
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
|
||||
|
||||
<more here>
|
||||
|
||||
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.
|
||||
Loading…
Reference in New Issue