UAV Tracking antenna
I have been thinking of ways to increase the range of the data modem or video feed from a UAV. And it always comes back to having better directional antenna on the ground that has to be pointing at the UAV. My problem is I don’t know too many people that would love to come with me to some remote area and hold a stick up to the sky with an antenna on it and point it at a UAV for hours at a time! I can’t see why?? :)
Then I thought it can’t be that hard to make a tracking antenna, can it??
Putting the mechanics of it aside for a moment….
If you had a GPS receiver on the ground (base station), and the feed from the UAV’s GPS it could be done. If you edited the Ardupilot code (another version running on the ground just for the antenna control) so that the GPS data from the UAV was constantly updated into the waypoint 1 position, and changed the rudder part of the code to give you a 360 degree value. This would give you the direction to point the antenna. Then all you would need is the difference in altitude between the two GPS units (Ground and UAV to get the height of the UAV), and then the distance to waypoint data to calculate the angle that the antenna would need to be pointing up from the ground. (Tan- x = altitude/distance I think?) Then all you would need is a reference to north (Compass module) to make sure it all syncs up. Somehow…
The only problem is if it lost track of the UAV it wouldn’t be able to find it again. Hmmmmmm..
This could even be used in a car following a UAV as long as the car was level and not going up or down a steep hill. I guess you could compensate for that as well if you had enough time on your hands.
I found this but there is not much info.
The hard part would be physically building the antenna mount.
I not planning on actually doing this anytime in the near future as I am still trying to build a working UAV but, can anyone think of a better way to do this?
Then I thought it can’t be that hard to make a tracking antenna, can it??
Putting the mechanics of it aside for a moment….
If you had a GPS receiver on the ground (base station), and the feed from the UAV’s GPS it could be done. If you edited the Ardupilot code (another version running on the ground just for the antenna control) so that the GPS data from the UAV was constantly updated into the waypoint 1 position, and changed the rudder part of the code to give you a 360 degree value. This would give you the direction to point the antenna. Then all you would need is the difference in altitude between the two GPS units (Ground and UAV to get the height of the UAV), and then the distance to waypoint data to calculate the angle that the antenna would need to be pointing up from the ground. (Tan- x = altitude/distance I think?) Then all you would need is a reference to north (Compass module) to make sure it all syncs up. Somehow…
The only problem is if it lost track of the UAV it wouldn’t be able to find it again. Hmmmmmm..
This could even be used in a car following a UAV as long as the car was level and not going up or down a steep hill. I guess you could compensate for that as well if you had enough time on your hands.
I found this but there is not much info.
The hard part would be physically building the antenna mount.
I not planning on actually doing this anytime in the near future as I am still trying to build a working UAV but, can anyone think of a better way to do this?
Replies to This Discussion
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Permalink Reply by Nick Sargeant on -
I'm glad people with the technical knowledge are pursuing this. Fantastic work.
From my limited code trading skills i take it that you planning to use Xbee modems to transmit the NMEA data back to the ground and also use standard servos for 180 degrees of movement. Is this correct?
Thanks,
Nick
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Permalink Reply by OlivierD. on -
There's a company in Holland, Immersion RC that makes FPV gear. They are about to release a full antenna tracking solution.
Here's the RCGroups thread. Apparently, they are demo-ing their units at an PFV meeting in France over the next couple of days.
http://www.rcgroups.com/forums/showthread.php?t=959889
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Permalink Reply by High Society on -
The Immersion RC system does look pretty nice but expensive. They do have some good ideas.
If I can write some interface code, I could put another modem and modem antenna on the unit in addition to the video and decode the telemetry which could completly bypass the laptop. Although I would have to integrate a GPS into the unit to get home position. I wonder if it would exceed the arduino's capacity with all of this going on?
Maybe then, I could forward the telemtry to the laptop for a complete ground station solution?
I was also thinking of adding a search mode in case of lost link. Any thoughts?
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Permalink Reply by High Society on
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Thanks for checking the code Jeff, I tried to do the math as simply as possible.
I haven't had much time to revise within the past few days as I have been out in the field.
Nick, I already have the modems in place that are transmitting the telemetry down at a rate of ~5Hz. I guess there are a few ways to connect the antenna pointer to the laptop and communicate. I had initially thought of using Azimuth and Elevation angles formatted in some way sent from the laptop. This way would reduce the math load on the arduino. I decided to go with the NMEA messages instead. Maybe in the future I may implement a STANAG message protocol. Or Cursor On Target (COT).
As far as actuation of the antenna(s), I am starting to get into that design phase now. Some concepts that I am keeping as priorities at this point are:
Power Consumption -- Because it will be running on a 11.1V LiPO
Durability -- I can see this thing getting beat around a lot in transit to and from the field
Accuracy -- I believe I can get around one degree of accuracy if I can get a good enough servo, polish the code and find a optical encoder or really good potentiometer.
With that in mind I was looking at obtaining a metal gear analog servo(for power consumption) for both az and el. The Azimuth servo will have its potentiometer disconnected and routed to an optical encoder(if costs permit) or a multi turn potentiometer in order to obtain a full 360 degree az rotation. I have implemented a similar 2 axis system on a board camera recently but at a smaller scale.
I have seen this done with a digital servo as the el actuator and a stepper as an az actuator which works great but steppers need a little more juice to operate. I also intend on reducing the duty cycle of the servos to help with power.
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Permalink Reply by Joel on -
Could the groundstation Xbee which is receiving telemetry from the UAV be used to point a tracking antenna? Maybe an additional arduino board could take in telemetry from the GS xbee and then send out ftdi to laptop for groundstation software and also use outputs to drive servos?
Also, the RTL variable could be used if you launch from where your antenna is. No need for a GPS on the ground? or even program in your starting coords before flying?
Anyone think this is doable?
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Permalink Reply by Joel on
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It seems that with this telemetry information already being sent through the xbee(including gps data), that there should be some kind of built in way to include antenna tracking. Is no one else interested in this? Would save space and money compared to purchasing a separate tracking device.
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ModeratorPermalink Reply by Sgt Ric on -
I was sure there was a group here at DIYDrones working on this... it had alot of discussion about a year ago with alot of interest at that time.
About the same time as the Ardustation work was being done. (the ArduStation manual even mentions the tracking antenna)
Jordi even had a prototype, if I remember correctly(?)
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AdminPermalink Reply by Thomas J Coyle III on -
Sqt Ric,
I believe that the latest version of the ArduStation firmware supported a tracking antenna and several forum members built pan and tilt antenna tracking mounts.
I have built the pan and tilt antenna mount for a diversity tracking system, but have not interfaced it with the ArduStation yet.
Regards,
TCIII
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Permalink Reply by Max on -
Hello. Yesterday i thinking about this problematics. My friend need tracking UAV because he have on UAV video transmitter on 5.8GHz. For good video signal, receiver antenna needs to be directed to transmitter antenna. My version of the solution of this problem is: On airplane is the GPS and RF GFSK modem module. RF modem module have omni-directional antenna and high output power. Frequency of the RF modem is around 430MHz. RF modem transmit the GPS data. Antenna ground tracking device have RF GFSK modem too, with omni directional antenna also (or one-direction antenna with wider angle then antenna for video receiver). For tracking you need to know only two angles: one is azimut second is latitude angle. You dont need to know distance from you to UAV. I attached the picture of the problem. On picture needed angles is gammaN and gammaH. From GPS data you can know the alfaA, bettaA, alfaL, bettaL angles. Also from GPS data you can know latitude (h). It is enough for rating needed angles. Before start you just to must calibrate ground antenna station. Software of the antenna tracking device need to know coordinates of the ground antenna placement. You just need to place UAV GPS-FSK modem traking module on ground antenna station and let software set this coordinates like ground antenna station coordinates. Then you need to turn ground antennas exactly to north and set this position like default. So now you can fly with UAV. Tracking device will rate azimut and latitude angles from GPS data and turn antenna exactly to UAV. So this is my idea.
P.S. Maybe the math problematic can be more simple. Amateur UAV will not fly on hundreeds kilometers. So i think that is possible transfer spherical tracking problematic onto plane tracking problematic. The rate code will be more simple and faster.
P.S.2 Sorry for my english. - Attachments:
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smerovanie antenn.PNG, 27 KB
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