picopilot+multiplex=trouble?

[Connexxion]

While seeking for a proper platform,I decided to connect the picopilot to my gear.

I've a Multiplex Cockpit SX tx and a Mpx ipd synthesised 7-channel rx.

Here are the problems I already discovered:

1:when enabling the picopilot both servo's (rudder and throttle) start to glitch.It doesn't stop and keeps on displaying this behaviour.

2:the picopilot doesn't perform a selftest at start-up.


I know there are issues with the futaba tx's,but does anyone know if mpx has the same problems?

I took a look at the german website of mpx and found this about the servoimpuls:

Servoimpulsformat: 1,5 +/- 0,55 ms (at maximum servotravel)

It doesn't say how many volts it uses.


Anyone with a solution? :confused:

[icebear]

Connexion,

I think it sounds like a signal level issue. If you can't get hold of servo boosters quickly, wouldn't it be possible to just test another rx? The cheap Hitech receivers work great and also Schulze receivers (which have failsafe).

Mind you, Multiplex have shifted channels compared to Hitech but is just a matter of checking which is which.

/Bjorn

[ThaiskyDigital]

Good guide icebear

[Connexxion]

Thanks Bjorn.

I did a test with a cheap tx/rx set and the picopilot did work.

It performed the selftest and didn't glitch the servo's anymore.

I prefer my mpx tx/rx and will have to get some servoboosters.

[kd7ost]

This thread might help.

Dan

http://www.rcgroups.com/forums/showthread.php?t=668465

[Connexxion]

Thanks Dan.

The only way to use that technic,is if you build me some since I'm absolutely not a volt-geek. ;)

[kd7ost]

:D :D

No problems. Most hobby shops have servo buffers. The problem is they don't all level shift so you would have to buy one and try it to see what chip they used and determine if it works. This is from the u-nav FAQ page.

How do UNAV units interface to RC equipment? UNAV units work with most modern RC sets. Some RC receivers like some Futaba PCMs, output pulse voltages that are too low for PICOPILOT to recognize so a buffer like the 605SB must be installed to increase the pulse level. If required, buffers are typically installed in-line with each connector to the RC-receiver.

http://www.u-nav.com/faqs.html

Bjorn,

Do you recall what brand you used in your applications? We almost need a list of off the shelf units that will do the job.

Dan

[Connexxion]

Thanks Kilo Delta,

I read that text this morning.

[icebear]

Bjorn,

Do you recall what brand you used in your applications? We almost need a list of off the shelf units that will do the job.

Dan

Dan,

I used both Cermark and Servo City boosters and they both worked fine with the FMA receiver. I am not sure if they would do the job for a Futaba rx though.
U-Nav have one of these in their product list I think.

Bjorn

[Connexxion]

I finally got the ordered 3 FMA servo buffers.

After a quick meal I connected everything to the picopilot/rx and switched the gear on...Yes!It did perform a self-test and the servo's didn't glitch like they did before.

This is what still concerns me:

1)-After enabling the picopilot,the rudder servo seems to have a new mid-point.

2)-After enabling the picopilot the rudder servo doesn't stand still and glitches some times about 0.5mm.The throttle servo does stand still.

3)-The manual says that one can take over control by moving the sticks further than 50% of movement.The throttle responds just like that but the rudder only responds when the stick is moved more than 50% to one side(R).When moving the stick the other side over 50% (L) the rudder doesn't respond.

I got the Alt3T version for altitudehold.
I was wondering if anyone knows if this device holds the throttle servo position it was engaged on.
So if one switches on the autopilot while the plane is flying at 75% of throttle,will the autopilot keep on cruising with 75% of throttle to maintain the altitude the autopilot was switched on(as long as the plane doesn't loose/gain altitude)?

Thanks in advance for reading my questions guys!

[Connexxion]

For those interested:

Just got an answer of multiplex.

The multiplex rx sends servo signals at 3 volts.That's less than futaba (3.3V)

[kd7ost]

I finally got the ordered 3 FMA servo buffers.

After a quick meal I connected everything to the picopilot/rx and switched the gear on...Yes!It did perform a self-test and the servo's didn't glitch like they did before.

This is what still concerns me:

1)-After enabling the picopilot,the rudder servo seems to have a new mid-point.

2)-After enabling the picopilot the rudder servo doesn't stand still and glitches some times about 0.5mm.The throttle servo does stand still.

3)-The manual says that one can take over control by moving the sticks further than 50% of movement.The throttle responds just like that but the rudder only responds when the stick is moved more than 50% to one side(R).When moving the stick the other side over 50% (L) the rudder doesn't respond.

I got the Alt3T version for altitudehold.
I was wondering if anyone knows if this device holds the throttle servo position it was engaged on.
So if one switches on the autopilot while the plane is flying at 75% of throttle,will the autopilot keep on cruising with 75% of throttle to maintain the altitude the autopilot was switched on(as long as the plane doesn't loose/gain altitude)?

Thanks in advance for reading my questions guys!

I don't know why the rudder would have a new mid point. Mine does not. When I let the GPS get lock, then enable the unit on the ground, the rudder doesn't move at all. Only if I move the plane away from the waypoint does it do that. Do you have waypoints programmed into the unit? If it's trying to navigate to a waypoint, the rudder will try to direct the plane that way.

The glitching is most likely normal. Does it cycle back and fourth slightly? The Pico pilot has rate sensors in it. Small amount of servo movement is normal once you enable the device. However, if the plane has a tail wheel or even a nose wheel, when the rudder does a slight deflect, it will move the rate sensor. The sensor detects that motion and moves the rudder the opposite way to correct, the wheels cause the plane to shift in that direction then reacts to move it back. You may see a cycling back and fourth when the plane is sitting static and the Pico Nav R is enabled. That would mean it's doing what its supposed to. When in flight the forward motion and fluid dynamics of flight come in to play and smooths things out. The plane doesn't go back and fourth unless the gain is set too high. For what its worth, much to the chagrin of unav I asked them to disable my rate sensors. I wanted rudder steering and use a co-pilot for roll control. I need my plane to fly flat because I'm set up to take vertical pictures. I wanted to rid any roll at all in my application.

I have never used the Alt T. I use the Alt E. I presume they work very much the same but have different contol loops to optimize its operation for elevator or throttle. The elevator can't be allowed to deflect as much as a throttle servo. My presumtion is, that the Alt T when acticated uses the BP sensor to detect if altitude is being gained or lost. The throttle servo then is changed to increase or decrease RPM to gain or lose altitude. In this case I would think the plane had to be set up so the motor thrust is a little high. That under full power you climb and with throttle off, you descend. The unit won't keep the throttle setting constant. It will adjust the RPM to gain or lose altitude. But you have to have the balance and thrust of the plane dialed in during the system integration process. You have to make your plane fly with the stick first as I described. Then you can put the Alt T on line and adjust its gains to optimize throttle settings for altitude control.

As far as number 3, I haven't used my system in that way. I only use it to return to me if there is intereference or what have you. I seem to recall though, and you would have to read the manual here, I thought the plane only responds to one direction of rudder stick deflection in order to circle a spot, while under autonomous control, and that releasing the stick back to less than 50% will allow it to resume on its course. I may be wrong on that. Maybe it is supposedto deflect either direction.

Dan

[icebear]

Hello again Connexion!

Dan got everything covered as usual, I think :), but just a few comments from me!

1) The servo for rudder deflects sometimes when you enable the Picopilot if you haven't got a valid GPS lock. Did you perform the test outdoors so that you had the GPS locked? Everything is probably OK here I think. A walking test outdoors would give you the answer.

2) Like Dan said - small adjustments can either be the sensors sensing movement or actual navigation - seems normal to me

3) I recall noticing the same on the ground once, but I believe it did work in the air. Not something I use very often...

The Alt-T works just as Dan described. In my setups the plane will gain a little altitude with more power, so the Alt-T will adjust throttle after the altitude it is sensing. If you activate the unit on a higher throttle setting, it still needs to lower throttle to maintain altitude, so you would not have a very much different result. Normally I just activate the unit on half throttle and that works fine - I have never needed to adjust very much to get the Alt T unit working fine.

I just found a nice airframe at Mountain Models - the Tyro 150 - 54 wingspan and 560 sq.in at 37 oz - seems perfect for a small UAV, so I ordered one yesterday!

http://www.mountainmodels.com/product_info.php?products_id=479

Good luck!

/Bjorn

[Connexxion]

Thanks a lot for your comments guys!

I have to admit I did the test yesterday without the gps antenna connected to the picopilot :o

I did another test today with the gps antenna and waited till the gps had a fixed position (both lights green).

The picopilot still has an offset of the rudder servo after enabling the system but this time the opposite direction.

I haven't installed the picopilot in a plane but did the test on my balcony. :D

It took the gps about 1 minute to get a fix and the picopilot did respond like KD7OST said.It looked like the picopilot was navigating itself to wp32.

I still don't understand why the rudder only deflects one side only (with the stick to the rightside).When moving the stick to the left,the rudder servo doesn't respond at all.This only occurs when picopilot is enabled.

This is what the manual says about manual override:

When the autopilot is in the ENABLED mode and the AILERON channel is
moved beyond 50% RIGHT, the autopilot responds with a controlled turn to the
right and will continue to circle as long as the channel remains greater than 50%.
Similarly, when the autopilot is in the ENABLED mode and the AILERON channel
is moved beyond 50% LEFT, the autopilot responds with a controlled turn to the
left and will continue to circle left as long as the channel remains greater than
50%.


Will order some Mpx planes as testplatforms like the Easyglider,Minimag and Twinstar.All will be the tuned versions.

http://www.natterer-modellbau.de/index.php/cat/c371_Combo-Sets.html

[Connexxion]

Just back from the balcony and I've found the solution to the oneway deflecting rudder servo----> A hard reset of the transmitter did the job.

The mid-point is now the same.Doesn't matter if the pico is enabled or disabled.The rudder deflects with the same amount of deflection to both directions.

The picopilot seems now solid and works like it should be.

As soon as I got my new platform(s) I'll install the pico to see how it performs in the air instead of a balcony :)

Thanks a lot for your comments and time you've taken to help me out.

[kd7ost]

Cool, good work sticking through it. And thanks again Bjorn for adding in the finer details. ;)

Dan