on my quad, pitch,roll and throttle are working fine. When in stabilize the yaw appears to have the effect of moving along the 5oclock to 11 oclock axis, although i have to land fast before it crashes. In stabilize with simple mode enabled the quad immediately yaws after takeoff. All other inputs seem to be ok.i dont think its a compass issue. i have calibrated the compass and transmitter. The motor test in the terminal is operating as expected. The props are matched to the user guide.the frame is an x config.
Any ideas as to what is wrong?
Replies
Motor adjustment (Rotor level adjustment) “Yaw problems during Loiter”
I found out that this aspect is somehow mentioned in the manuals, but it’s important is not as high mentioned as it should be.
Background:
In the past I bought some frames from Chines shops and it tend out that their quality (also as a consequence of the price) was from not so good to very poor. This was reflected by a misalignment of the vertical axis of the Motors and by that the misalignment of the rotor level of all used Motors. Of course a defined rotor axis inclination may improve flight stability, but only if it is defined and not if all rotor levels have random-wise different level inclinations.
Evidence:
I recognized during flying my Quadrocopter in Loiter mode that Yaw was not proper performed. The copter was rotating not around it’sown vertical axis. It was using a virtual axis approx. 50cm away from it’s frame and it was floating away from its original loiter position hold by the GPS. After I stopped the yaw command it took approx. 15sec. for the copter to find its original GPS position. (The copter was not tuned so far.)
Remedial Action failed:
After I analyzed the log, I recognized that the PWM output for two Motors (from four Motors) was significant higher than the others. So I interexchanged the Motors and calibrated the external Magnet sensor again. (The ESC’s I am using cannot be calibrated.) This was not changing the situation. I was a bit irritated because I used other Motors before with the same application, adjustments and Props and that worked without problems.
Remedial Action:
During the last test flight I then recognized that the rotor level of the Motors werea bit different. So I build a test/measurement setup to align the rotor levels on an even plate and adjusted all four Motors so that the rotor level of all motors was within the range of approx. ±0,5mm.
As you can see based on the Motor PWM output, now all motors are more or less in the same range especially during Loiter, when there is no wind.
This tuning helped to make the copter flying very precise now.
PK, do you find that those arms vibrate in flight - i have the same ones (Cheap chinese i think) and i believe that under the weight of my quad they are vibrating and resonating to the point where the quad becomes unstable like i show in the video below.
Hello Damo,
I am using the following setup:
Motor 2830-14 750kV from RC-Timer
ESC 30A with Simon K Firmware from RC-Timer
10x4,5 full carbon Props from RC-Timer
Spyder X4 Fame from RC-Timer
LiPo 3300mAh S4 nanotech from Turnigy sold by HK
With the S4 you have the right Prop speed in correlation to the weight of your Quard. The Motors are getting warm but not too much max. 45°C.
The weight of my system ready to start is 1400 gr.
It is important to balance your Props. There is a good YouTube Channel from Painless360 who describes in a very good way how to balance perfect. (He also has much more very interesting videos…)
https://www.youtube.com/watch?v=-vakWrc86xE
Also as described the Motor axis must be within a small range (I would say +-0,5mm) perpendicular to the Multicopter horizontal axis. Important is to use vibration damping as much as possible. I already send the link to the frame I also use. Avoid cables coming from the frame (e.g. Receiver who is on the frame direct mounted) and lead into the APM to not create a “vibration bridge”.
Of corse my frames are vibrating but this does not play a big roll because of the measured vibration level on the APM.
Here the vibration level I am in now…
In general I think that more then 500gr of additional payload my QC can not carry. Please think about the weight to lift ratio.
Following some pictures that describe the motoraxis alignment procedure as PDF file.
I hope that helped you to eliminate the issue you have.
Best regards Peer
QCopter Motor adjustment.pdf
Another issue that I have in mind is maybe the amount of log parameter. How much parameters do you log.
Only log what you like to test ..not more. During a flight today without logging my system I had the impression that the system was more stable. Maybe because of the more on calculation power of the APM.
excellent work. one can also use the other approach - add tape to shim between the motor and motor mount at the appropriate screw.
also, careful how and what you measure.
#1 rotating each prop tip to a stationary measure tape, primarily measures the perpendicularity of the prop to the motor (the prop to motor interface). This is a common problem even with high quality propellers.
#2 putting the prop perpendicular to the motor mast and measuring to the floor at each tip, primarily measures how level the motor mount is to the ship (the motor to mast interface) in the y direction (common issue with bolt-down motor mounts).
#3 putting the prop parallel to the motor mast and measuring to the floor at each tip, primarily measures how level the motor mount is to the ship (the motor to mast interface) in the x direction (an error here is not as common).
Do #1 first followed by #2 or you could end up chasing a tail.
All,
thanks for the input.I recently bought new motors and new carbon fibre props.Lets call this SETUP-A. Note the motor is mounted on an extended piece for the following Reason.
SETUP-A
After listening to Forest and Randy i now mounted the motor directly onto the fram - making sure that the screws dont extend into the motor wiring. Lets Call This SETUP-B which i tested yesterday.
SETUP-B
Now SETUP-B solves the yaw issue but there is a twitching and jumping - I think it's one or more of the motors is vibrating. So i think with the new motors, New Much Stronger props (old were APC) and the weight of the quad, that resonance is making a play here. See the following Video
So basically i think my quad is not strong enough for the weight - I was going to buy this.
What are your thoughts on the matter ? And if you have any other frame suggestions then i am open to suggestions.
A high speed camera would be useful.
Impressive. Quite the beast!
Engineering rule #1. Never add dead weight.
For example, a metal extender was added. This:
- adds weight
- requires higher rpm and vibration to lift
- weakens the copter (makes it less stiff)
- better to use nylon bolts for the motor (subtracts weight) that can be cut to the perfect length so as not to damage the motor (also eliminates the need for the redundant X motor mount.
Engineering rule #2. Stiffer is better. Holding the copter firmly to the ground, pull down on the end of a motor mast and let go. If you can make it vibrate (more than up/down/up) then it is not stiff enough. If it bends more than 6mm when normal payload weight is applied to it, it isn't stiff enough.
Engineering rule #3. Use good rotors. The plastic props shown are inefficient. What are the carbon props you just got?
Can I assume that you don't feel comfortable building your own? There are parts of your copter that are adequate and could be used on a stiffer, lighter, stronger frame you could make yourself.
I'm not familiar with the frame you are considering buying.
Forest,
These are the Carbon props.
Can I assume that you don't feel comfortable building your own? I prefer to buy.
You know i think tomorrow evening i will try to prove my theory by making the existing frame very light - i.e remove the landing gear + camera and use a smaller battery. Does this sound like a good idea - At least it will prove in theory that a stronger frame should sort the issue.
Yes, brilliant idea.
also consider removing the motor extenders and find the correct size bolts or get nylon ones (or aluminum or steel) and cut them to the correct length. You've inadvertently added a diving board. Then test.
The carbon props are plastic with carbon fiber fill. It makes the plastic stronger. Haven't tested those props. The best 11" props I've seen so far are: APC 11x5.5 C-2 or GemFan 11x4.7 AG-G.
forest, so i rebuilt on a new carbon fibre frame. it hovers at 80% throttle for about 2 minutes. yaws to the right a little bit and then drifts down. i give it 100% throttle and it still drifts down. i have tried all of my batteries.same symptoms. i am at a loss here now as to what the issue is. i have attached two short flight logs.
2014-09-11 22-47-18.log
2014-09-12 10-08-26.log
-
1
-
2
-
3
-
4
of 4 Next