U-NAV Pico Pilot problems

[dgamble]

Hello,

I'm working on a project at Oklahoma State University and we have purchased the PicoPilot from U-NAV (http://www.u-nav.com/) but we are unable to get it working with our Futaba PCM receiver. Our problem is we can't get the Pico Pilot to turn off.

We are using a Futaba PCM 138DP receiver and between the RC-Rudder and Nav Enable on the Picopilot we have boosters in place to step up the voltage to 5 Volts but the we still can't turn it off. We can get it to work with our FM receiver but we don't want to use FM because the signal is not secure enough. There is a cell tower outside of our lab which broadcasts alot of noise and we have signal loss with our plane when we are more than 3 feet away. PCM works prefectly.

We are planning on using the auto pilot to help fly our plane over 200 miles and set a new world record for F5S category (electric aircraft, 5kg limit).

We have checked that our boosters are boosting the signal to 5v and they are so we don't know what else to do now. U-nav has been trying to help us be we have not had any success yet.

If you guys have or had a similar problem please let us know.

Thanks

-Dustin

Project website.

http://aerodesign.okstate.edu/projects/dragonfly%20page/dragonfly.htm

[workshop]

Forget the boosters. Futaba uses 3.3v logic and that's the core problem. You need to replace the receiver with a JR (or similar... I use JR without any problems) that uses 5v logic signals.

Boosters are a band-aid on the core problem. Fix the problem. :D

Jeff

[dgamble]

Thanks alot Jeff.

I'm not sure if we are ready to replace all of our Futaba radio equipment yet. It looks like to use a JR PCM Receiver ($89) you must have a JR transmitter ($250) too.

I wish there was another way we get it to work with Futaba Transmitter. We have it specially modified so we can plug an external car antenna into it and also run it off of an external power supply for the long range missions.

[kd7ost]

There are some issues with the Futaba PCM radio that come up alright. I use the same system on my plane and discovered a couple of things. The 3.3 vdc logic levels like you describe. It sounds like you have them level shifted though. The other issue is not likely hurting you but if you have a dual trace scope maybe you can look at it.

The Futaba PCM receiver creates the pulses to the servos in pairs. It's not one servo, then the next, then the next, etc until it sends a pulse to all the servos then starts over again. It sends 1 and 2 then 5 and 6 then 3 and 4 then 7 and 8 and then starts over. Individual servos don't care. But some devices, like the FMA co-pilot, cannot deal with two pulses getting there at the same time. It needs to process one, then the other etc.

I doubt that is the problem if you're using channel 4 for the rudder and any other spare channel for the enable line.

Are you using the Futaba T8UAP transmitter with that receiver?

What spare channel are you using to enable it with?

Can you plug a servo into each of those two channels, Rudder and enable, and get them to work?

Does the spare channel used for enable, move the servo through it's full range? If the radio is set with End point or throws really minimized to one side, it might not be changing the pulse duration enough to disable the unit. Make sure that channel is set for 100 percent throw on both ends.

Dan

[workshop]

"We are planning on using the auto pilot to help fly our plane over 200 miles and set a new world record for F5S category (electric aircraft, 5kg limit)."

Back up a minute. You want to set world records and $350 on critical radio equipment is too much to spend?... Your project manager needs to help the engineering team set priorities, IMO. :D

I know money at the college level is hard to come by but I think a quick design review might save some (more) headaches at this point. There are those on this forum that will help (myself included).

Jeff

[nschoeps]

We've had some similar experiences using our Futaba receiver and the pico system. We've had the most success using hitec receivers with the Futaba tx, however we're using PPM at the moment. We've also had great success using castle creations berg receivers, which have the advantage of being programmable.

Nick S.

[dgamble]

Thanks alot. I was able to get it to work if I put the Nav enable on channel two and then rudder on the alerion channel. When I put the eleron stick at full up it turns off and when I move it all the way down it turns on. Now I'll try putting it on a more usable channel.

We have transmitter T8UAP.

[dgamble]

Ok our problem is fixed.

I just moved the Nav enable from the toggle switch 5 to the twist knob 6 and it turns it off and on everytime. We hope to start testing the pico pilot with the World Record plane ,Dragonfly, and hopefully be able to go for the range record before the end of the year!

Thanks guys!

[workshop]

Glad you were able to find a work-around. The offer still stands about design review help. There are a lot of talented guys on this forum who have helped me with many problems. I just hate to see a double band-aid approach (boosters and non-intuitive channel assignments) in a mission critical project.

ESPECIALLY since you're working on a college assignment and I'd like to think that ground-up decision-making is part of the learning process. I deal with very high risk physics in my job and so I'm tuned to that sort of thing. Bad decisions kill more people/projects than bad physics. :rolleyes:

This is not to say that what you're doing is life threatening; that's my job. :D And I'm not saying you're making a bad decision even though it runs counter to what I'd do. ;)

Good Luck... Jeff

Jeff W. Parisse
www.teslacoil.com

[kd7ost]

I use the same radio and receiver in my Pegasus plane and it has now logged in excess of 2,000 miles travelled with no issues. I use a Jomar Opto-isolated glitch buster and separate my receiver and electronics power source from my electromechanical power source operations that way. It also level shifts all the pulses.

I don't think it's a band aid to use the servo amps. Thay're made with CMOS 4000 or 74HC series 4049 Hex buffers. The job of those IC chips it to square pulses but also allows you to provide logic level conversion using one supply voltage. Good stuff.

There are certainly systems that allow more plug and play capability without as much integration. I agree it would be cleaner or use less parts to go with a serial style servo output but don't think anyone is doing anything complex or counter intuitive in his description. Channel 5 or some other spare channel should be used for the enable line anyway so it's intuitive once you set it up and get used to using it.

I use channel 5 to enable one UNAV product and channel 6 to enable my other UNAV product so that is intuitive to me.

Just my opinion, but even though with the right spending you can simplify things, I don't think they are doing the wrong thing by learning how to integrate 3.3 volt logic levels to 5 volt TTL devices.

Dan

[workshop]

Dan,

All that is fair... I was trying not to be too hard on the guy; my level of fail-safe may be different than his. :D

My main design focus was RF crossover and I found that buffer amps didn't help or in some cases made worse RF noise that got to the receiver. No problem since any good receiver front-end notch filters will clear this up.

I think that a Auto-Pilot-Off situation may be accompanied by high stress factors and that makes turning a knob "counter intuitive" compared to hitting a simple toggle switch. You were the guy that warned me about keeping things simple because the landings are almost always high stress. Months of testing did not reveal this truth. Only actual jobs did.

I want these guys to succeed and I think they can benefit from some of the help available here. You, Icebear and to a lesser degree me had to start from scratch on a lot of this stuff (hence the 3.3v to PicoPilot evolution, the WP import issue (now solved), some of the electrical system isolation and rudder mixing stuff I've played with).

Jeff

[kd7ost]

I think you and icebear are the field experts on the Pico Pilot system now. At least with the Nav A systems. I like the Nav R and Co-pilot. Dave doesn't like me using that combination but I'm not even flying autonomously anymore unless it's return to Pilot.

Anyways, Good work from all you guys. ;)

Dan

[icebear]

That's a very kind comment Dan! :) I'm a 'heavy user' at least..
I too have used one of my systems together with the Co-pilot. It worked well, although I now use the Nav-A only which works really well.

Does anyone know if Hitech has any PCM receivers with failsafe? Would be great to skip the buffers I need to use with my FMA FS-8 rx..

/Icebear

[workshop]

The Bergs have it I believe...

Jeff

[dgamble]

After getting the auto pilot to turn on and off with the knob (channel 6) I noticed that when I was adjusting the knob it was set on the transmitter to be 140% in both directions. So when I rotated the knob about 3/4 it turned off and then rotating it the full way turn it back on. Using that knowledge I fixed my toggle switch (channel 5) to only go 100% in both directions and it worked perfectly. Before I had it set to 140% is both directions.

Yesterday we did our first test flight with the Dragonfly and the pico pilot together and we flew a short 12 miles course. The autopilot hit every way point and it worked great. Next we are going to try the altitude hold.

Another thing we haven't test is turning the pico pilot off and then back on again and seeing if it will contiune the course. Say we are doing a range flight in a straight line. The next waypoint is 10 miles away and we just passed the previous waypoint 1 mile ago. If we turn off the auto pilot now and then turn it back on will it go backwards to the waypoint it already passed which is closer or will it go to the next way point 10 miles ahead?

Dustin

[workshop]

Good work on the toggle switch; it'll make more sense the one day when you really need it to... ;)

I looked over your site. I didn't realize when I gave my initial advice that you were so far along on your project. For the 200mi run, what telemetry are you going to send back if you are allowed under competition rules? If not, then I guess that what the chase car is for... :)

In so far as the PicoPilot On/Off question... it's funny but we've never tried it. We have a go/abort decision tree and if "abort" we manually land. We're always flying under "UAV VFR" (I made that up... RCAPA can trademark it if they want :rolleyes: ) so a visual recovery and landing is not difficult.

Jeff

[icebear]

Good to hear about your progress!

If you by "turn off" mean DISABLE using the switch the Picopilot will go for the next WP in line (for example WP no 5 if you DISABLED after WP4 and the ENABLE again). This is my understanding at least.

If you turn the Picopilot off (power down) it will start over from WP no 1. I don't know if its advicable to do this in the air considering the calibration that happens upon startup.

/Icebear

[dgamble]

Yes, I meant disable and thank you I figured it would go to the next waypoint too, although I was curious if anyone had tested it. For our mission we might need to disable the autopilot for a brief time for a bathroom break and then enable it again continuing our course.

For the range mission we are going to have to follow in a car. The FAI official observer can never let the plane out of his sight during the entire mission. They don't allow him just watching a monitor while it reads a downlink tracking the plane's position using.

Our first attempt on the range mission was to fly from a camera onboard the plane and a TV inside the car. The pilot would just fly the plane using the camera downlink to the TV and the driver would just follow the plane. But we wanted to relieve the pilot load because the whole flight will last up to 8 hours. Other problems we had was that we had some reliability issues with our camera and it consumed almost one watt which equivalent to 60+ miles.

Dustin