Taranis: Aileron-To-Rudder Mix. - RC Groups
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Apr 14, 2017, 08:26 PM
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Miami Mike's Avatar
Mini-HowTo

Taranis: Aileron-To-Rudder Mix.


An auto-switching aileron-to-rudder mix for the Taranis
For OpenTX version 2.1.9

Aileron-to-rudder mix is useful but there are times when you want rudder control to be completely separated from aileron control. A common solution is to turn the mix on and off with a switch, but here I'll describe a setup that does the switching automatically. It works like this:
  1. When the aileron stick is moved away from center while the rudder stick is centered, aileron-to-rudder mix is active.
  2. If at any time the rudder stick is moved away from center, the mix is automatically cancelled and the rudder stick takes full control of the rudder. The changeover is slowed slightly for a smooth transition.
  3. When the rudder stick and aileron stick are both centered, the mix is reactivated.
In other words, the rudder is controlled by one stick or the other but never both, and the rudder stick has priority.

A simplified eepe file is attached that demonstrates the setup, and if you have glidsim.lua installed in your /SCRIPTS/TELEMETRY folder you'll be able to watch it work. Activate the glidsim screen with the PAGE button. In Companion simulator, use the [Hold X] function to set the aileron stick away from center, then move the rudder stick and watch what happens.

Note: Of course the attached eepe file is not meant to fly a real model. It's only for demonstration purposes.

In this example, GV1 is used to set the amount of aileron-to-rudder mix. The value should be between 0% and 100%. I have it set to 75%.

For switching between Mix On and Mix Off, I use an input:
Code:
[I5]ARSW MAX Weight(+100%) Switch(L3) [Mix On]
         MAX Weight(0%) [Mix Off]
The automatic switching is done with three logical switches. When L3 is true, aileron-to-rudder mix is active:
Code:
L1 Rud ~ 0
L2 ( Ail ~ 0 ) AND L1
L3 Sticky(L2, !L1)
The mix happens in the rudder channel:
Code:
CH06 (Rudder) MAX Weight(GV1)
           *= [I5]ARSW Weight(+100%) Slow(u0:d1)
           *= [I2]Ail Weight(+100%) Edit: Add "NoTrim" to this mix to prevent aileron trim from affecting the rudder.
           += [I4]Rud Weight(+100%)
I hope you find this useful. Please check the comments below for changes and suggestions, and if you have any questions, comments, or suggestions of your own, please post them.

Last edited by Miami Mike; Apr 16, 2017 at 10:14 AM.
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Apr 15, 2017, 06:02 AM
Registered User
mikeshellim's Avatar
Mike, interesting application and solution.

Here's an optimisation, same logical switches, but without the need for an extra input.

Code:
CH06 
    [I4]Ail Weight(GV1) [AIL]
 *= CH10 Weight(+100%) Slow(u0:d1) [RAMPDN]
 += [I1]Rud Weight(+100%) Switch(!L3) [RUD]
CH10 
    MAX Weight(+100%) Switch(L3) [A2RENABL]
As far as I can tell operation is the same, i.e. the aileron input ramps down when over-ridden.
Apr 15, 2017, 08:40 AM
Registered Taranis User
Miami Mike's Avatar
I fixed your input assignments to match mine and added your version to the eepe file for comparison. Yes, the end result appears to be the same.
Latest blog entry: Taranis: Aileron-To-Rudder Mix.
Apr 15, 2017, 02:25 PM
Registered Taranis User
Miami Mike's Avatar
I've realized that there's a problem with both of our versions in that aileron trim affects the rudder. The cure is to add NoTrim to the mix:

My version fixed:
Code:
CH06 (Rudder) MAX Weight(GV1)
           *= [I5]ARSW Weight(+100%) Slow(u0:d1)
           *= [I2]Ail Weight(+100%) NoTrim
           += [I4]Rud Weight(+100%)
Your version fixed:
Code:
CH06 (Rudder) [I2]Ail Weight(GV1) NoTrim [AIL]
           *= CH10 Weight(+100%) Slow(u0:d1) [RAMPDN]
           += [I4]Rud Weight(+100%) Switch(!L3) [RUD]
My regular setup doesn't have this problem because I knew about the need to use NoTrim when mixing ailerons to rudder, but when I created the simplified eepe file I simplified it too much! As Einstein is popularly credited with saying, "Everything should be made as simple as possible, but not simpler."

By the way, there's another problem with your version in that rudder trim doesn't work. The cure is to remove "Switch(!L3)", which doesn't really do anything else beside disable the rudder trim.

Here's another eepe file with all of the corrections so far:
Latest blog entry: Taranis: Aileron-To-Rudder Mix.
Apr 15, 2017, 04:46 PM
Registered User
mikeshellim's Avatar
Well spotted re rudder trim. However your fix (to include it with the rudder mix and to remove the !I3 switch) also means the rudder mix is active at all times. This is at odds with your description which said "In other words, the rudder is controlled by one stick or the other but never both..." ;-) That was the reason for the !L3 switch.

If the aileron and rudder inputs were mutually exclusive, the rudder trim could be implemented as a separate mix with src = TrmR. Love these OpenTx conundrums
Apr 15, 2017, 05:32 PM
Registered Taranis User
Miami Mike's Avatar
Yes, the rudder mix is active at all times, and yes, it's also true that the rudder is controlled by one stick or the other but never both, and the rudder stick has priority. There's no contradiction there.

Try removing "Switch(!L3)" from your version and see for yourself that the only thing that changes is that the rudder trim works.
Latest blog entry: Taranis: Aileron-To-Rudder Mix.
Apr 15, 2017, 06:54 PM
Registered User
mikeshellim's Avatar
Quote:
Originally Posted by Miami Mike
Yes, the rudder mix is active at all times, and yes, it's also true that the rudder is controlled by one stick or the other but never both, and the rudder stick has priority. There's no contradiction there.

Try removing "Switch(!L3)" from your version and see for yourself that the only thing that changes is that the rudder trim works.
Yep, I stand corrected
Apr 16, 2017, 01:01 PM
Registered User
Sensoar's Avatar
Miami Mike, thanks a bunch for sharing the rudder aileron mix. I will give it a go today and see how it works.
Apr 20, 2017, 04:55 PM
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Sensoar's Avatar
Hello Mike, thanks a bunch for all the great work with the Rudder Aileron mix. It works great. I just have a quick question. The Aileron to Rudder mix works when using the aileron stick. When using both sticks there is no mix which is perfect and a brilliant solution.

This issue is... what I am seeing is about 20 percent of the time when using both sticks there is inadvertent mixing of the rudder with the aileron. I also notice that on the simulator that from time to time L3 is triggered on and stay on occasionally.

Thanks in advance for any thought on the mix.
Apr 20, 2017, 07:02 PM
Registered Taranis User
Miami Mike's Avatar
Yes, that's what you'd expect. Whenever both sticks are centered at the same time, the aileron-to-rudder mix is reactivated. If you can think of an alternate way that you'd like to see it work then it'll almost certainly be possible to program it that way. Any ideas?
Latest blog entry: Taranis: Aileron-To-Rudder Mix.
Apr 20, 2017, 07:11 PM
Registered User
Sensoar's Avatar
Ok, I get it now. I will fly with it this week and check it out in the air. It seems like a very clever way to have the mixing when you need. Thanks again.
Aug 28, 2017, 11:06 AM
Registered User

looking for Miami Mike


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You would of course be given credit for the photo.

The book has an ISBN 0-9711637-1-5, you can find it listed in Amazon but there is no reference photo of it, I just looked. I would be happy to provide any other info if you have questions.

Hoping you can help, Keith
Aug 28, 2017, 12:58 PM
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Miami Mike's Avatar
Replied by private message and email.
Latest blog entry: Taranis: Aileron-To-Rudder Mix.
Aug 30, 2017, 08:02 PM
Multifaceted Heli Nut
heli-headcase's Avatar
Back to the auto Ail-Rud mix for a minute - I just found your blog and consequently set up my own manual (switched) mix to assist in hand launching a powerful electric model. I like what you've done but would prefer a small modification to it.

How about initializing the flight with your mix active but disconnecting the mix (for the remainder of that flight) once the rudder is moved beyond a defined threshold? Logical switch programming is something I'm trying to grasp but I'm just not one to configure conditional situations. Thanks
Aug 31, 2017, 04:59 AM
Registered Taranis User
Miami Mike's Avatar
If you've upgraded to version 2.2 then that's something I haven't gotten into and don't expect to in the foreseeable future, but if you're using 2.1.9 I can have a look at it. I'll need your eepe file to know how to add it to what you already have.

Also, you'll have to specify how the mix would be reactivated. In other words, you'll need to decide how the radio would know that a flight has ended and a new flight was beginning.
Latest blog entry: Taranis: Aileron-To-Rudder Mix.

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