Stabilizing Roll Control

[Garth]

Hello all,

I have recently installed roll and pitch servos in my FD180 (with latest S/W) equiped Sonex. Pitch (SV32 servo) set-up has been pretty easy although I haven't really tested it under varying conditions. But today it was holding the altitude within 10-20' in level flight. It did lose about 50' during a 180 degree turn so it may still need a bit of tuning.

However roll control seems to be more of a challenge. I have tried the full range of sensitivity settings and something in the 12-16 range seems to be the "best" so far, controlling within 3-4 degrees of set point in calm air. While this may sound quite good, the plane noticeably rolls back and forth to achieve this, which of course I would like to substantially reduce. After 30 minutes I was starting to feel slightly noxious so if I had a passenger ... well staying on auto pilot for roll control may have been cut short. No idea why, but roll control only has the sensitivity adjustment, while pitch control has sensitivity plus several other secondary adjustment options if needed (only one of which I have tampered with so far).

Any suggestions to help stabilize the roll servo from the group and Dynon staff??

Thx

Garth

 

[Dynon]

A few tips:

Use track mode instead of heading mode while you're testing/adjutsting - the former relies on heading which is often imperfectly calibrated in many aircraft, and introduces errors into the AP.

Next - if you haven't already, turn the turn rate to 0, and set the bank angle limit to something reasonable (25-30 degrees, max). This puts the AP into its alternate bank angle control mode, which is actually the basis for SkyView's AP. We basically redesigned the AP lateral algorithm, made it an option, and then decided it worked so much better that it's all you can use in SkyView. The software on your D180 still allows either control scheme, though.

 

[Polaris]

May be self-evident but don't forget you have no yaw damper, so any rudder or torque inputs will interfere with the roll smoothness and effectivity. I damp out or augment/reduce yaw manually during all flt regimes under A/P : turns, straight/level flight and climbs /descents. Gives me far crisper turns to headings and Nav tracking with little to no wallowing.    mike.

 

[Garth]

Thanks for the replies. Re the Dynon reply, I don't se ethe Track option on the menus which I presume is becasue I do not have a GPS connected. Correct?

Is the alternate bank angle option independent of having/using track mode?

 

[Dynon]

Yes, the alternate bank angle option is independent of those.

And if you don't have a GPS connected to the D180, track mode won't be available. Do you have any GPS in the cockpit available that you might be able to connect? Track mode will most likely improve your best performance with the autopilot.

 

[Garth]

I am using a 7" Nexus 7 tablet with Nav software as my GPS so no serial port available to connect to the D180. I was thinking of buying a bluetooth to serial adapter and connecting this to the 180 and see if this works. Thoughts?

http://www.rovingnetworks.com/products/RN240

 

[Dynon]

It looks like Naviator has documented support for doing just that. There's a chance it could work.

Any self-contained GPS receiver/antenna puck that outputs NMEA at 9600 (see http://wiki.dynonavionics.com/GPS_Serial_Compatibility_and_Configuration_Settings for the sentences that you need to get out of it) should also work. SkyView's won't work, incidentally, because its baud rate is much higher.

 

[Garth]

Update - flew a cross country yesterday and the AP worked great. The altitude is especially good, holding to within 10' with changes barely notiicable. Roll control is much better with the alternate control mode. It seem that a high sensitivity setting (20-25) works best, but some minor rolling is still present, although tolerable, better would be nice.

For a possible bluetooth to serial adapter, does pin 9 on the Dynon DB9 connector provide a source of power? Info needed to select the correct Roving Networks adapter. Thx.

 

[Garth]

OK, I found out that the DB9 connector does not provide any power, so I will need to figure out which of the battery powered adapters from Roving Networks will fit the need. I will see if Roving Networks can provide some guidance.

 

[Dynon]

Only the serial tx/rx/ground pins (2/3/5, I forget which are which off the top of my head) on the Dynon DB9 are used on our serial connector.