Hello,
I finally have my T-rex hooked up properly to my Pixhawk and everything seems to be operating perfectly except the internal Pixhawk gyro is reversed. I would imagine it would be a very simple setting, but I have not found any info on it in the forums or online. So far i have reversed channel 4 manually in the Spektrum Dx8 transmitter and also RC4_REV in the System Parameters of the APM Planner, and all combos in between. No matter what I do, the gyro continues to move the rudder the wrong way.
Any help is much appreciated!
Thanks,
Evan
Replies
Wiki has a good instruction about how to tune the controller, and it's explicit for traditional helis. http://copter.ardupilot.com/wiki/traditional-helicopter-tuning/
Looking forward to your good news.
Hi Evan,
That's sort of an odd issue and I can't see what's happening. Is your Pixhawk mounted right-way-up, and you have it defined as such in the parameters?
You probably should leave the channel in your radio not-reversed. Then make sure the RC Input in the radio setup page is not-reversed. Now when you move the yaw stick, the slider in the radio page should move in the correct direction. (ie: move stick left, bar moves left). Then, you simply reverse the servo output in the Heli Setup page to get the rudder servo moving in the correct direction.
There doesn't need to be any separate gyro servo reverse. It's all handled as long as you have your RC Input working the correct direction.
Oh, do this test:
Try arming. Does it arm with the stick left, or the stick right?
Right, so I don't have an external gyro, just the rudder servo.
So even when I have the settings so that the green bar moves right, it arms when I hold the stick right, and it yaws right when I turn right, the gyo still sends it into an endless spin.
I agree with you guys that the system should just "know" since your basically telling it which way is which...that's why I'm pretty confused and out of ideas. They only way I can think of a quick fix is manually rotating the servo horn 180 degrees, but that will cause stress on my control rod.
Also, on the radio calibration page I don't have the "reverse" buttons like they show on the tutorials online, so I am only playing with the transmitter's channel reverse and the Parameter list options. I've included screen shots...
Screen Shot 2014-04-16 at 10.36.14 PM.png
Screen Shot 2014-04-16 at 10.36.51 PM.png
Evan,
We took those rev switches off the radio calibration screen because they should never be used.
On the mission planner heli set-up page there is a servo reverse button. You know. maybe the REV you need is not on the RC4_REV but the HS4_REV.
Ah, nice catch. So he was reversing the Ch4 input with RC4_Rev, right?
Wow! Randy you are right, HS4_REV reversed the gyro only! This is exactly the setting I was looking for.
Whats also interesting is that I don't have a heli setup section like in that link that you provided, I am running APM Planner 2.0.8...
Thank you very much for the help.
Just took it off for the first time with the Pixhawk, everything was looking good until after about 3 seconds the cyclic started going crazy and the whole copter shook like crazy and had to land. I attached a short clip.
Any ideas off the top of your head what settings I should look into? I am a complete beginner with these autopilots so I am still learning. I will research this issue now in the meantime on the forums.
IMG_0738.MOV
I would leave the Rate Roll and Pitch values at zero for now. Later on you can try a few very small amounts like 0.0050, but not yet. It'll just complicate things.
So I would suggest to reduce Rate Roll and Pitch P terms as Randy suggests. You'll probably find the wobble goes away but you'll have zero control. In that case, try adding Rate Roll and Pitch FF. I forget the value off the top of my head, I've posted my parameters a few times. I think something like 0.0500 should work.
I-term on helicopters can be quite a bit bigger than the P-term. You should probably run 0.100.
Cool!
So the wobbling will be because the Rate Roll P and Rate Pitch P are too high probably. Maybe drop them to 1/2 what you have there. "I" can be set the same as P. No need to worry about IMAX. Not sure about what D should be but generally it's very small.
You've probably already seen the TradHeli wiki but here it is just in case.
Splitting the problem is a good move. So first make sure that the yaw input is correct by going to the mission planner RC configuration page and checking that the green bar moves in the same direction as the transmitter's stick. So move the yaw right, the green bar should move right. If it doesn't then you need to reverse the pitch channel in the transmitters.
I think RC4_REV's value should be either -1 or 1. You tried setting it to -1 I guess?
Hey Randy,
Thanks for the quick response. Yep, I've made sure that the yaw moves the green bar right and changed the values between 1 and -1 in RC4_Rev but all that does is reverse the direction of the servo when I move the yaw stick on the transmitter, not the gyro's compensation direction. So for example, when I try to take off and lets say the nose yaws right, the gyro compensates the wrong way and continues to add more yaw right, instead of left to keep it straight.
I feel like there should be a gyro reverse option somewhere, like there is on most separate gyros for RC heli's that I've flown.
Maybe this helps describe my problem further. But yes, I think I've tried all the combos of reversing yaw from the transmitter side as well as in RC4_Rev.
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