Quad HT-FPV control problems

[jdjeff]

I just sent the text below to the designers of this frame. Haven't got a response yet. But in the meantime, I was wondering if anyone in here has the same frame and could offer any guidance.:

Just curious if you could offer any suggestions here. I have an HT-FPV frame with Naza M FC. I have been fooling around with gain settings trying deal with some control issues. Seems like at times, the quad just fights me when I try to turn left durung fast forward flight. Slow flight seems fine. I never seem to have the issue if I'm turning to the right. The other thing that happens is a semi violent wobble on a right or left turn in forward flight....as if the quad is trying to find level and fighting to go straight. Up to this point, I have been tweaking on the gains and it seems like when I think I got the problem fixed, the gains are now causing other problems such as oscillating as if the gains were to high. This happens in attitude mode. In gps mode, as I experienced last night, there was one point where it would not turn left at all until I flipped it into attitude mode.

In an effort to fix this (and as suggested on rcgroups), I replaced the esc's with simon K flashed esc's. I also replaced the motors at that time. I got the stuff from rcmanchild. But the problem still persists. It's making me think about the aerodynamics of this frame now.

Ok..I'm not really requesting you to diagnose the problem. But I would like to find out since the frame is not symmetrical, how does this affect the gain settings? I have been keeping the pitch and roll 'basic' gains the same. But I'm thinking that perhaps the pitch should be different from the roll and it could be the reason I'm not getting this quad COMPLETELY under my control. If you could verify this and tell me a good starting point on 'basic' gains? I'm not sure if the shape of this frame would dictate the pitch gains be higher than roll or if roll gains should be higher than pitch. Any help on this would be appreciated since I can't seem to find a good answer out there. Thanks.

 

[Lee]

One point i can say is, you should have the roll and pitch gains set differently. Pitch should be more sensitive the the roll as the quad is longer than it is wide. But i don't see at the moment how this would affect your yaw. Have a look at the yaw gains.

 

[jdjeff]

That's the kind of info I was looking for. I was having some yaw issues where the nose kept wandering around in straight flight. So I kept turning yaw gain up until I got it to stop. But then it was jumpy when yawing with the stick so I backed it off. Then I started seeing the wobble again.

Here are the last gain settings during yesterday's repeated wobble fligths.

Basic Pitch 125
Basic Roll 125
Yaw 143
Vert 145
Attitude Pitch 131
Attitude Roll 131

I'm not exactly sure what vertical does. I kept increasing it because it seemed to respond better with throttle. When I had vert gain at 130, it didn't seem to climb out of trouble fast enough. I could be totally wrong on that assumption.

With the gains above, I seem to have pretty good response during a low flight right off the deck. There is a cart path at one of the fields I go to. I noticed that raising the gains to where they are now, I have good response and can follow that cart path without worrying about over/under correcting around that path. It feels like I'm in complete control. But take it up in the air, then the woblle kicks in during those left turns.

But if the pitch is actually more sensitive than roll, this may be (part of) the problem.

- - - Updated - - -

p.s. My total weight is 1.825 KG I'm using 10x4.7 inch CF props on 1000kv motors. 3S 6000 mah battery.

 

[Lee]

I'm not familiar with the Naza set up. I am an Open Pilot board user and KK2.0. All i can say from experience is, test one thing at a time until it seems to react as you want it, then move onto the next. Good luck.

 

[jdjeff]

I'm beginning to wonder if this is a 1.3 ghz Vtx interference issue. It's sporratic which is making it hard to troubleshoot. But this seems to happen at distances that are out of visible range.

 

[Stambo]

Just a thought, have you tried it with smaller props?

 

[jdjeff]

Stambo...this quad is a longggg story. Maybe most of them are. To answer your question, yes. I tried 9X4.5's and couldn't get the lift I needed for the larger battery. And I never tried to get a smaller battery because I'm hell bent on longer flight times. It has occured to me to try the recommended 3300 3s and 9" props. But I'm being a little stubborn about starting all over with this thing.

All the stuff on this frame was moved over from a similar shaped 450 frame with DJI arms. I didn't like how flimsy the arms were so I bought this frame. On the old frame I was actually using a 6400 3s. I was getting 13 minutes flight time. And it didn't have these control issues. I tried the same battery on the HT-FPV and decided to back off to the 6000. I fabricated a battery tray and the battery mounts underneath.

It's true that I may be beyond the design limits of this frame. But there are times when I give it left turn stick commands and it just keeps flying straight.