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Old Aug 07, 2009, 09:59 AM
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Joined Sep 2007
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Originally Posted by Neo360
This is my test for Return to Home look the parameter and video of my Twin Star II.

What is the correct parameter?

RTH engaged at 3.09min of video, i have connect the rudder and elevator, is better aileron and elevator?
First, I'd strongly recommend you leave it connected to rudder and not aileron. If you are getting that much movement with just rudder, if you switch to ailerons you're probably going to be doing barrel rolls.

Next, I'd try to eliminate as many variables as possible because there is too much going on at the same time to be able to know what to do.

So, for example, try having the OSD only control elevator/throttle OR rudder. Personally, this is what I would do.

Don't have the OSD control elevator by setting these values to zero:
Pitch Proportional Gain: 0
Pitch Derivative Gain: 0

Then setup the rudder control to use proportional gain only like this:
Turn Proportional Limit: 20
Turn Proportional Gain: 10
Turn Integral Gain: 0
Turn Derivative Gain: 0

As for throttle, I would personally try to get the OSD to use a fixed throttle setting in order to eliminate that as a variable for now too. From your video it looks like if you pull between 6 and 8 amps that you can hold altitude pretty easily.

I would find the stick position on your Tx that corresponds to between 6 and 8 amps and program that stick position for all 3 of the throttle questions in the RTH wizard. As I've noted in a previous posting, there is a risk that if you ever invoke RTH on the ground that the prop could spin up if you do this so be careful!

With that done, I would get in the air and check that my trims were good because for this test the OSD is ONLY going to be moving the rudder. With throttle and elevator fixed, you want to be sure that your plane isn't going to nose dive.

NOTE: If you have to play with your trims in order to maintain level flight you MUST land and reprogram the RTH wizard again so that it is aware of these trim values. Bill P is going to be coming out with a feature that will eliminate having to do this but for now it's what you have to do.

If your trims are all good, I would then turn on Display Servo Deflections from the OSD Display menu. Then I'd initiate a very gentle turn and watch the rudder values to see how much rudder movement it takes in order to turn the plane. Let's say it takes +/80 rudder deflection to do a gentle turn.

Now then, earlier we programmed in a pretty small value for Turn Proportional Limit. Engage RTH and be ready to take over in case your plane takes a dive. Watch the servo deflection values and see how much rudder deflection you are getting. Adjust the Turn Proportional Limit value until RTH gives you whatever amount of deflection you established would be good (+/80 in our example). For now, don't worry if the plane overshoots home on the turn.

Spend some time playing with the proportional limit until you can get a nice gentle turn. Then, once you feel like you have a reasonable setting, start adding some Turn Derivative Gain. Maybe start with 5 or 10 and move in increments of 5. Derivative Gain will "smooth" out your turn so that it doesn't get too fast and will help prevent overshoot.

Sorry, this is getting long and I need to move on to something else here. I'd start with something along those lines and get to the point where I would see a smooth turn. Once you have established that you can get a smooth turn, then I'd start playing with the elevator values in a similar fasion, starting with a low value and slowing working up.
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