Fast ascent causes quad to bank and pitch. Need help.

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Maverick

Member
I've been flying my DJI WK-M X650 v4 for some time now. All be it fairly docile and not aggressively. As my confidence grows, I try pushing it that little bit harder, and there's no problem, apart from one thing - when I give it more throttle suddenly, not gradually, it tends to not go up in a straight line, but banks off to the right a little, and pitches back a little. I'm using torxpower 900kv motors, with Graupner 10"x5" props. All are perfectly balanced, as it hovers excellent in ATTI, and holds excellent in GPS HOLD, and video is smooth also. The CG is also perfect, so I'm wondering is it something to do with my vertical gains...??? I've only flown in ATTI & GPS ATTI modes, as I trust them. I tried MANUAL once, and the quads altitude dropped very fast, so that freaked me out, and I never tried it again. (Is this normal?)
If its of any relevance, I have an AeroXcraft GoPro gimbal mounted, powered by a separate CC BEC, and controlled by the WK-M.
As I said, if I fly calmly, and don't do anything mad, there's no problem, but, sometimes I'd just like to do a bit more fast dynamic flying, and at the minute, I'm limited.
Any advice folks...???

Mav.
 

kloner

Aerial DP
is this 3s or 4s? whats the AUW? what are your gain numbers like?

do you have any footage that we can hear the motors running?
 

matwelli

Member
It always shoots off in the same direction ? Check your esc endpoints. Slo flying the fc has time to compensate, hit the throttle and it won't have a chance. A weak motor will also do the same (uneven thrust)
 

Maverick

Member
is this 3s or 4s? whats the AUW? what are your gain numbers like?

do you have any footage that we can hear the motors running?


Sorry for the delay in my reply. Time difference - bed time.

It's 3S. The AUW is 1.969KGS. Autopilot gains are :

Basic Gain : pitch & roll are 110% ; Yaw is 140% ; Vertical is 135%

Attitude Gain : both 70%

No Advance Parameters.

I'm running 5.08fw.

I can make a video later on, and post it. (Weather permitting)
 

Maverick

Member
It always shoots off in the same direction ? Check your esc endpoints. Slo flying the fc has time to compensate, hit the throttle and it won't have a chance. A weak motor will also do the same (uneven thrust)

Yes Mat, it always shoots off in the same direction. It's been doing it from day one - it just never bothered me til now, as I was always flying nice and slow. How do I check my esc endpoints... My Radio Tx...?
 

ATFlyer

Member
Sounds like ESC calibration and/or possibly timing to me too.
I would think since it flies OK calmly it's not your gains. Your ESC instructions will tell you how to calibrate them.
Take your props off when you do it because at some stage in the process it'll probably involve you setting full throttle. (The motors SHOULDN'T turn but better safe than finger-less!!!)
 

Maverick

Member
Thanks for your input ATFlyer. It was custom built for me by a dealer, and he set all ESCs to high timing. They are T-Motor 18A ESCs. I have checked timing on all four motors, using a programming card, and they are all high.
On low throttle, before take off, all motors are spinning equally, and all make the same sound, so motors seem ok.
When I showed dealer, he just said, "Don't accelerate fast. Keep it nice and gradual".
Strange!
 

kloner

Aerial DP
make a video..... it'll let us hear the problem, if nthe cam can point in the direction it goes, even better. we can see props speed up, slow down or hold speed..... the noise should tell the story
 


Droider

Drone Enthusiast
When you coming over matey.. we could have a look at it then but sounds like one of the motors aint keeping up with the rest.

When you say fast do you mean banging the stick forward?

How fast can you throttle up before it does it/

Does it even out when it gets up to speed?

I would recommend you upgrade firmware to 5.18. Its much smoother if that the right word.

Dave
 

Maverick

Member
Well Dave,

I'm tied up with work til about the 2nd week in March, so can't get away for a weekend. But anytime after that. When suits you, and well set a date. Hopefully by that time, weather should be much better... I can take all over with me in the jeep, and get everything up and running properly.

I don't even mean banging the stick forward, if I push the stick from 50% up to 75%, it will do it. I just have to rise it slowly.

It doesn't even out - I have to pull back on the throttle again, to steady her.
 


Droider

Drone Enthusiast
BTW.. Love your avatar but can you not crop this as after all you are Borg!

attachment.php
 

Maverick

Member
Oh yea Dave, we'll maybe drown the shamrock!
I'm going to post a video of the way it ascends, I can email you a partial of it, keeping it short. It will be tomorrow now, as its getting dark here now, and I'm still not home.

I'll work on my new avatar... Ha!
 


mrbonk

Member
As others have suggested, you may have an ESC that isn't giving the same full throttle response as the others, or you may have a motor that's not quite as good as the rest.

Re the craft dropping suddenly when you go into manual mode, where did you have the throttle stick when you switched? If you were at mid stick and it dropped, you're probably overweight for your chosen prop/motor/battery combo. Ideally, you want the craft to hover at mid stick in manual mode. This gives you a good, balanced power to weight ratio. More importantly, it also means you have power in reserve to arrest a descent when required!
 

Maverick

Member
As others have suggested, you may have an ESC that isn't giving the same full throttle response as the others, or you may have a motor that's not quite as good as the rest.

Re the craft dropping suddenly when you go into manual mode, where did you have the throttle stick when you switched? If you were at mid stick and it dropped, you're probably overweight for your chosen prop/motor/battery combo. Ideally, you want the craft to hover at mid stick in manual mode. This gives you a good, balanced power to weight ratio. More importantly, it also means you have power in reserve to arrest a descent when required!


Duely noted mrbonk. When I switched to manual mode, I was hovering in ATTI mode @ mid stick. Maybe the throttle needs to be re-calibrated, so as to hover at mid stick in manual mode...?

Thanks for your input.

BTW, dealer said it was normal for craft to drop, when switched from ATTI to MANUAL.
And normal for craft to rise, when switched from MANUAL to ATTI...
 
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mrbonk

Member
Duely noted mrbonk. When I switched to manual mode, I was hovering in ATTI mode @ mid stick. Maybe the throttle needs to be re-calibrated, so as to hover at mid stick in manual mode...?

Thanks for your input.

BTW, dealer said it was normal for craft to drop, when switched from ATTI to MANUAL.
And normal for craft to rise, when switched from MANUAL to ATTI...

I'm not sure throttle calibration is your problem. I suspect your craft is simply too heavy for the chosen combination of motors/props/battery. I should have checked to see if you told us what gear you're using before I started typing :) Anyway, you can do some basic calculations based on the combination you have that will tell you roughly how much thrust you can achieve. I'm at work at present, so I don't have the bookmarks I need, but I'll see if I can find them when I get home.

Your dealer is correct, insofar as there being a potential difference between the control boards 'mid stick' throttle setting and how much throttle you actually have on at 50% of your throttle travel. As I said earlier, ideally you want these to be the same (or close enough), so either you need more thrust or less weight to achieve this. In your case, when you have your throttle stick at its mid point, the control board is actually forcing the speed controllers to deliver more than 50% power to achieve a hover.....so, when you go to manual mode and you get your 'actual' 50% power, it doesn't have enough thrust to hover anymore.

Both of my current craft are slightly overpowered, so when I go from atti to manual, they climb. This is about to change with the addition of a gimbal and some FPV gear though ;)

EDIT: I found one of the thrust calculators - http://www.lcrcc.net/thrust_calc.htm
 
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Maverick

Member
Ahhh! Now that makes sense alrite! I understand what you mean...

I'll apply the thrust calculator, and see if I'm underpowered, for my AUW, before I start 'dissecting' motors or ESCs, for a fault.

thanks mrbonk, and everyone else, for your info, you've been very helpful.

I'll still post a vid later, so you all can see for yourselves.
 

Maverick

Member
Well, I finally got to the bottom of this problem, and she's flying perfectly now!

My wee bird had been lying up ever since, doing absolutely nothing! Recently I bought a Tarot T-2D BLG for it, so I decided to tackle the problem again... I changed motors and ESCs, but to no avail - still the same results!

Also, if I give it full yaw suddenly in either direction, she'll dip down on one side, but if I slowly give it full yaw, no issues at all, except if I release the yaw stick suddenly, and let the spring centre it - then it dips down again!

So I tried it with a 4S lipo... Problems gone!

Fast ascent - no problem! Straight up!
Fast yaw - no problem!
Fast yaw stick release - no problem!

Glad to get it sorted, but I'm still sort of puzzled as to why such a big difference in 3S and 4S...? Why did it make one motor look dodgy...? I thought if it was under powered, it would just be sluggish, not unstable in a particular direction...?
 
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