Tricopter - servo shaking

[rihardsb]

Dear All,

Does anybody have an idea why tricopter tail servo is shaking during and after calibration via GUI, gyroscope/accelerometer calibration and accelerometer trim. While tricopter is positioned horizontally, tail servo turns the tail chaotically to both directions. I use Multiwii firmware version 1.7. The values read through GUI seem reasonable and the output from the sensors seems fine! Has anybody came across the same problem?

Best Regards,
Rihards

[rihardsb]

The only answer to my question I found is to reduce vibration to absolute minimum, however I am wondering, is it possible to do it programatically via firmware?

[Alexinparis]

you can try this:

#if defined(TRI)
gyroData[YAW] = (gyroYawSmooth*2+gyroData[YAW]+1)/3;
gyroYawSmooth = gyroData[YAW];
#endif

=>

#if defined(TRI)
gyroData[YAW] = (gyroYawSmooth*4+gyroData[YAW]+2)/5;
gyroYawSmooth = gyroData[YAW];
#endif

[rihardsb]

Thanks Alex:) I'll try that!

[trobinson3003]

richardsb,

did the above solution work for you? I tried it but my tricopter still has an intermittnet jerking while flying.

Tom

[bill516]

I've got this problem tail servo shakes even without motors turning. Thought I'd fixed it at the w/e when I uped the tail servo rate to 1 in the GUI, after that I managed to fly a bit despite the wind. Had a go today with as it wasnt too windy and the servo was shaking as bad as before.

re the info from Alex above, where in the sketch does it need to go.

[PatrikE]

I have same problem on my gimbal.
Using A0 & A1.
When the Tilt-Servo moves it starts to shake.
In the gui i can see that when it starts shaking all RX inputs is flickering between 1000-2000.

It seems that the servo is overloading the output.

Iw'e tested some servos and it occurs on another to.
The servos is 9gr MG servos.

With a Turnigy TG9e it's normal.

/Patrik

[bill516]

Found the gyrodata part in the code and replaced it, it is much tamer now but still shaking, its flyable but does not hold a heading needs correcting now and then. I also reduced YAW P to 10 and that made an improvement as well. Naffed another servo so need to replace that before I can try more tweaking, I've had enough for the day so will try later

I thought the post from Alex was two different things to try, it was only when I did FIND 'gyrodata' in the code I found that the first code Alex mentioned was already there, so I replaced it with the bottom code.

[zarkon]

I have same problem on my gimbal.
Using A0 & A1.
When the Tilt-Servo moves it starts to shake.
In the gui i can see that when it starts shaking all RX inputs is flickering between 1000-2000.

It seems that the servo is overloading the output.

Iw'e tested some servos and it occurs on another to.
The servos is 9gr MG servos.

With a Turnigy TG9e it's normal.

/Patrik

I have the same servo on my small tri same thing happen it start to shake for no reason now my tri has become quad so no way to test it again, But I personally think it you using 9gr MG get another servo I tested w/o connecting to multiwii is shaking as hell

[Poofjunior]

I had a very similar problem where, despite my pid settings, after every initial power-up, any slight touch on the rear of my tricopter would send it into a constant shaking. It ended up being a design problem: it turns out that the thing aluminum tubes that I used were very good at propagating vibration from the motor all the way down the shaft to the center where the sensors are. I couldn't get stiffer tubes at the time so I changed the design altogether from thin hollow aluminum to pieces of balsa wood reinforced with carbon fiber cloth. This change eliminated the problem completely! Now, when daydreaming about frames, I have to keep two things in mind:

1. Try to keep most of the weight of the frame at the center, rather than at the ends of the beams (where the motors are).
2. Dampen the center with beams that will either absorb a good amount of motor vibration (like wood), or remain stiff, so that the vibrations of the motors must shake the entire quad rather than just the ends. When the beams are flimsy, they can let small vibrations accumulate at the ends of the beams, like a ball-on-a-spring being bounced at just the right rate to build up the intensity of the movement.


I hope this helps!