UAV - Where to start?

[seddto]

I am just at the beginning but i would like to build my own UAv even if this is a long way to go i think :D The "Ready to Go" Autopilot systems(like Micropilot) are a bit above my budget(around $5500 above my budget i think :D ) so i have to do it my self i think. I read about the OpenSource-Projects like Paparazzi or RCpilot - this would be a good solution. The problem is: I have very little experience with this microcontroller chips they are using :( I don't know where to start to get this working (How to connect the chip to the rc reciever, how to plug the gps with the chip, how to get the Autopilot software on the chip etc...). It's a little bit like a few thousand small pieces and you don't know how to get them together :D Does anyone knows some good sources of information for the beginning? I am from Germany - perhaps anyone even knows a good german forum about Model UAV's - or some good german websites perhaps? I hope it's a bit easier to understand in german ;) Thanks for help Stefan :)

[icebear]

Hello Stefan,

A good way to start if you don't want to build your own stuff could be to start with a simple setup like the U-nav NAV2 board and a GPS. This costs approx $500 instead of the $5000 for the Micropilot. The NAV2 board gives you a possibility to create a route with 31 waypoints and connects directly between the receiver and servos. I used a FMA copilot ($99) like a lot of other people have done to stabilize the airframe. Check the Unav webpage www.u-nav.com and my thread about "Ferias goes UAV" from a few weeks ago if you don't already know about these units.

Und ja, ich spreche auch ein bisschen deutch falls du einige Fragen hast!

/Icebear

PS: I am a little interested in the Paparazzi stuff as well but haven't gotten into it yet

[seddto]

Thanks for your reply icebear :) I didn't notice the NAv2-Autopilot yet - sounds interesting. But what kind of senors are included - i didn't get it from the description on u-nav.com. Is a IR-Sensor used to detect the wing level? I also heared about the Ap4 , one is sold at ebay at the moment. Would this be a good choice?

[kd7ost]

Thanks for your reply icebear :) I didn't notice the NAv2-Autopilot yet - sounds interesting. But what kind of senors are included - i didn't get it from the description on u-nav.com. Is a IR-Sensor used to detect the wing level? I also heared about the Ap4 , one is sold at ebay at the moment. Would this be a good choice?

How are you doing icebear?

Seddto,

UNAV doesn’t use any of the thermopile type sensors in their products. They use all MEMS sensors. (Called SMM by Futaba) The thermopiles, like what are used in the co-pilot, operate well most of the time but there are certain atmospheric or terrestrial conditions where they cease to get the job done. I have a few and they rarely work in the winter time for example when the ground and air infra red temperature signatures are too close to each other. Even in some drab cloudy conditions I’ve had no stability from the co-pilot. The Co-pilot is a good device so don’t get me wrong, but it’s built for hobby flying and most hobby fliers are also fair weather fliers. If your UAV flying is going to be for hobby or other fair weather work, it shouldn’t be an issue for you to use one though.

There are different versions of the PICOPILOT flight systems that are optimized for different styles of aircraft. A full blown PICOPILOT system will stabilize and guide most conventional style stable airframes. This means in roll, altitude, (altitude lock using barometric sensing) as well as managing the GPS waypoints in a route. It can operate small electric aircraft with tiny little blind GPS units or bigger gas powered aircraft. The one thing you won’t find in the PICOPILOT line is the ability to change altitudes throughout the flight using autonomous means. It stays at the altitude you set it at. You can override this in flight but altitude changes are strictly a Pilot function while autonomous flight is under way. That’s something I think is generally acceptable in this level of UAV product. It’s not meant to allow your plane to head off to NAS. I also think most guys like us doing this are more interested in ourselves as the Pilot making the decissions during the flight. The autonomous systems working or poised in the background are used more to supplement the pilots job when needed. All this despite the fact that it (PICOPILOT) can perform full autonomous flight and is an off the shelf system.

I have one unit and am looking to get another variant soon. icebear has just worked through getting his going so he’s up on a fair amount of the setup information. When you buy a PICOPILOT, UNAV provides access to the manuals and documentation that takes you to the nitty gritty.

I don’t know the AP4 unit. A couple of guys have used it. Look down the list here for a whole thread on the AP4. http://www.rcgroups.com/forums/showthread.php?t=417175 I know it uses GPS information for guidance and altitude. This information comes from a handheld GPS which outputs the NMEA 0183 information at a 2 second rate. So you can’t expect altitude to stay real tight. In my own usage I find pro’s and cons to using a handheld GPS unit too. There’s a whole gamut of information you are about to get exposed to.

Let us know if you have any more questions.

Dan

[icebear]

Hi Stefan (& Dan!),

I just got back from another (good!) UAV flight at the beach where I live, so it feels appropriate to respond now...

Dan pretty much covered everything with his really informative reply, but here are a few comments from me too.

The NAV unit is only one half of the Picopilot - it performs winglevelling (if you choose the NAV-A(ileron) unit - the NAV-E(levator) does not) and navigation, but does not include the altitude hold unit. If you are using the FMA co-pilot you could use this unit to keep the plane level but it is hard adjust throttle and elevator to keep the plane from gaining or loosing altitude a little.

I found that just using the Pico NAV and Copilot works for shorter routes and for experimenting, but for longer routes you'd need some kind of altitude hold.
The ALT board in the Picopilot can be purchased separately, so it could be an idea to get some experience first with just the NAV unit if you want to save some money...

Anyway, best of luck!

/Icebear

[icebear]

Hello again Stefan,

Here's a picture from today at dusk when I flew a short UAV mission (2 km's approx or 1.5 miles).

This is my Super Impress II, which is a small electric (42" wingspan, 30 oz AUW) with the Picopilot and FMA copilot. You can see the thermopile sensor (black) and GPS (yellow) on top of the wing/fuselage.

Keep us updated on your questions and progress!

/Icebear

[Jeff85]

Thanks K.... & Ice....
for all the good info on getting started in UAV's. I know it helped me a lot understand more about what I have to do to my own ship I'm building, when I get to the UAV aspects.

Check out my build thread post 250, 251, 269 & 275: http://www.rcgroups.com/forums/showthread.php?t=394769&page=17&pp=15

I will certainly be over here to gain more wisdom from you all when I ready.
Thanks

[icebear]

Thanks Jeff!

I have been reading your thread before with great interest. Good to see that you received your eagletree stuff now as well! Keep us updated on that. I've been thinking that you might be able to use an existing navigation GPS to load the Eagletree so that you don't need to have one for telemetry and one for navigation. Would be interesting to know if the Eagletree system accepts 'any' GPS or if the Eagletree GPS outputs standard NMEA sentences that could be used for the Pico for example... Any idea?
Good luck!

/Icebear

[seddto]

Hello icebear - Thanks for help and the great pictures! Now i understand how you do the alt hold part - that seems pretty tricky :) But i am still wondering how reliable these NAV-A and NAV-E Autopilots work, perhaps anyone could say a bit about that. Does the NAV-E just hold a altitude the plane is flying or can you tell the NAV-E perhaps after takeoff climb to 200 ft and hold? How is the NAV-E managing the "climb rate" and avoids a stall? Perphaps anyone has some experience with this autopilot? :)
Still some questions on the NAV-A, perhaps icebear knows a bit about that :rolleyes:
If you plan a gps route for the NAV-A to fly, can you start this route everywhere or do you have to bring the plane in a good position to start so that the Autopilot only needs to do little course changes (perhaps 1-2 degrees)?
And: Does the NAV-A regain control in extreme situations perhaps after a stall or while flying with a high bank level?
So many questions - sorry :D I am still learning a lot on these things, thanks for help :rolleyes:

[icebear]

Hi Stefan,

The NAV-units navigate through aileron (-A, incl wing levelling)) or Rudder (-R no wing levelling) and the altitude hold units are called ALT (-T for throttle or -E for elevator).
The altitude hold is not programmable, when you enable the device it will try to keep the altitude you were at when the device was enabled. So for example you take off manually and climb - when you are at the desired altitude, turn on the autopilot and it starts to navigate and keeps the altitude.
I have no experience with the ALT_E, but the ALT-T works fine.
And finally when plannig a route you should allow for the turning radius. In practice I have had no problems at all. It goes from waypoint to waypoint as long as these are spread out more than 1/10th mile apart.
Since I am using the COpilot to stabilize I havent had any extreme situations to recover from. The NAV-A wing leveller however is limited to 45 degrees bank angle I believe.
Hope this helps!

Icebear

[kd7ost]

Hello icebear - Thanks for help and the great pictures! Now i understand how you do the alt hold part - that seems pretty tricky :) But i am still wondering how reliable these NAV-A and NAV-E Autopilots work, perhaps anyone could say a bit about that. :

They are very reliable. I can give you some information and I know icebear will jump in too.

Does the NAV-E just hold a altitude the plane is flying or can you tell the NAV-E perhaps after takeoff climb to 200 ft and hold? How is the NAV-E managing the "climb rate" and avoids a stall? Perphaps anyone has some experience with this autopilot? :) :

Pico Pilot is made up of two proprietary circuit boards that can be used alone or in pairs. You must have GPS to go with them. For waypoint management you use a Nav board. This comes in two flavors. Nav R or Nav A. R=rudder steering and A=aileron steering. The Altitude hold also has two flavors of Alt boards. The Alt T or Alt E. Both altitude flavors, The Alt E (Elevator) and Alt T (Throttle) use a barometric sensor to keep your UAV at the altitude you set. You don't tell it how high to fly. You fly via RC to the altitude you desire and enable the device right there. The Alt E will control your Elevator to keep the UAV right there. It has a gain adjustment built in. During the setup you test this in flight until the gain is correct for your airframe response. The Alt T does the same thing and is used in airframes where altitude is lost or gained by using the throttle. Not all, (In fact very few) RC planes are set up that way. I like the Alt E in my gas powered plane and the Alt T for electric. The motor in an Alt T setup needs to have a little more up thrust than the kit manufacturer calls for so it will gain altitude when throttled up. Stall is avoided in the setup and proper choice of airframes. Picopilot is not designed for unstable (aerobatic or pitch sensitive) aircraft. Generally trainer type airframes with a little nose down balance are used for stable UAV platforms. I would speculate that high wing planes flying slower than 100 mph are best to use with Picopilot. Control to prevent a stall is easy then. The device doesn't take you to an altitude. It keeps you where you set it. If you set it while in flight, then lose engine power, but have a plane set up for slight nose down pitch angle, you will just descend normally. The control throw won't go radical and cause a stall unless you have it set too sensitive on a plane that is prone to stalling and have a large elevator surface area. Thats not generally the case though.

Still some questions on the NAV-A, perhaps icebear knows a bit about that :rolleyes:
If you plan a gps route for the NAV-A to fly, can you start this route everywhere or do you have to bring the plane in a good position to start so that the Autopilot only needs to do little course changes (perhaps 1-2 degrees)?:

The Nav units will turn you a complete 180 degrees if needed to get to the next waypoint. There are some limitations but I don't remeber them ver batim. It shouldn't be a problem. Things like if your next way point is over 100 miles away it will skip that waypont assuming you must have errored in the data entry. The waypoint manager will follow your waypoints to the letter otherwise. It does not do the "Smart Route function" that a handheld GPS does. If you put in points that go back and fourth, it will sequence back and fourth to them. UNAV wanted to rectify the guidance problems that handheld GPS software imposes.

And: Does the NAV-A regain control in extreme situations perhaps after a stall or while flying with a high bank level? :

Yes, if it's enabled. If the plane is set up correctly with the PicoPilot, those extremes should never happen. It would take a massive wind gust or something really out of the ordinary to induce a bad aircraft attitude. The response time of the MEMS sensors used in Pico pilot is faster than a pilot could react. You shouldn't see any problems like you describe.

So many questions - sorry :D I am still learning a lot on these things, thanks for help :rolleyes:

Dan

[seddto]

Hello icebear & kd7ost: Thanks for your help :) It's not so easy to understand how those autopilots work, when you never have seen one "in action" :)

[icebear]

No worries Stefan. I got all the help I needed from Dan and others here, so just keep asking!

Icebear