Great deal on a 3 axis gimbal with Alexmos controller

Gary McCray August 5, 2015 at 11:20am

Hi Euan,

I pretty quickly came to the conclusion that factory settings are not really workable.

The power and + settings really need to be modified. - (increased).

Probably higher power or + on the yaw will fix the yaw losing sync problem, I had that at lower settings on yaw and pitch.

And I know the PIDs need to be "tuned" to reduce the jitter.

Some of the effects looked like they might be more related to the camera too though.

I have my gimbal working pretty well statically as far as maintaining sync and low jitter for my laser rangefinder, but it can still benefit from more tuning.

Best,

Gary

Euan Ramsay August 5, 2015 at 1:20am

Btw guys, this is my first run with this gimbal. Completely factory settings. The results leave a lot to be desired.

Gary McCray August 2, 2015 at 9:35am

Hi Dan,

Do you have yaw set to Invert?

On mine, the yaw definitely needed to be set to Invert with pitch and roll set to Not Invert.

And Chris,

Using those settings, on mine yaw seems to be working correctly although it may need to be cranked up a bit in power or additional (+) power.

Definitely it isn't glitchy. It doesn't twitch at all when sitting still or when moving.

I did have a problem with pitch twitching, but that was solved with current settings.

I am using a 2S battery and if you are using more cells, the power and + figures may need to be adjusted.

Best,

Gary

Gary McCray July 26, 2015 at 6:52pm

Hi Chris and Euan,

Chris, the P value at 1 seems a bit light for Yaw, since P is the primary portion of a PID it would reduce response amplitude / speed.

And I do think the power figures are a bit high, perhaps more so for a 3 cell versus my 2 cell.

Possibly decreasing the power but in some cases increasing the + factor could be a better solution.

Primary "Power" (I understand) equals static holding (continuous) power versus "+" which equals temporary increase while moving power.

Also has anybody tried the 6 way calibrate?

(Damn hard to implement in the real world.)

One of the reported symptoms of not doing that was the slow drift in yaw which I have also seen, but am not currently having a problem with.

Interesting that when it is upside down there is Pitch changed to inverted which you would expect and Yaw changed to not inverted which you would also expect and roll not changed from not inverted which takes a minute to figure out but which also seems right.

I do wonder a bit that possibly the gimbal itself, although balance-able upside down might still not function optimally because of the increased off angle weighting.

(I want to turn mine upside down too, but will be interested to see how yours works out).

Interesting also it took so long to turn 45 degrees with your limit set to 5 degrees per second it should take 9 seconds at maximum rate.

Mine is actually working pretty well right now, but I know the PIDs are going to need to be tweaked for maximum performance and power probably isn't totally optimal for me yet either, (I need a fast manual move rate for scanning).

Best Regards,

Gary

Euan Ramsay July 26, 2015 at 1:19pm

Chris, did you not have to set AXIS RIGHT to -Y, so pitch was listed correctly?

Euan Ramsay July 26, 2015 at 1:09pm

I get a very, very slow drift in yaw on mine. I had to bump power to 160, and Yaw D rate to 20. Apart from that...I just need a window to go test time.

Gary McCray July 25, 2015 at 6:53pm

Hi Dan Further Work with results as followed.

Input recommended starting settings from DYS Gimbal PDF page 9 of 9

I set PIDs, Power, Invert pitch and yaw as shown and changed from 14 poles to 22 poles and unchecked skip gyro calibration at startup and wrote it.

Still problems and not right and yaw definitely not right so please see below, actually got things working pretty well.

First you need to do setup with both battery and USB connected (I am using a 7.4 volt battery so not sure about bigger ones).

OK

Num Poles = 14

Roll P 13, I .2, D 17, power 110, +0, not invert

Pitch P 12, I .11, D 9, power 100, +25, not invert

Yaw P 18, I .23, D 17 power 130 +25 INVERT

Try this, it seems to be working pretty well for me now doing setup with battery and USB connected.

Auto Motor Configuration doesn't work worth ####.

But I set power and invert values based on actual behavior until achieved apparent decent operation.

At least it's a place to start.

Pretty clear these are 14 pole motors though by looking at spread from auto (13, 15 and 16) and not 22 pole motors as mentioned in the DYS PDF manual.

Actually looking to be working pretty well now - including default yaw behavior.

Best Regards,

Gary

Gary McCray July 25, 2015 at 5:16pm

Hi Dan,

Just a quick thought, I have read that when you power the board from the USB it doesn't power the 3rd (yaw) axis ESC (although on mine Yaw does work to a degree, sort of, somewhat, not very well but it's trying).

I am using a 7.4 volt battery and with direct battery power Yaw follow actually works pretty much as it's supposed to when powered.

I have now updated my firmware (required to use the GUI I downloaded from Basecam) and now the Alexmos boards clearly need recalibration and reinitialization.

It is stable but if you move the base of the gimbal to fast or far it can lose sync.

But at least it now comes up and shows a green LED solid connection rather than a (green LED blinking) error.

I am going to follow the initial setup instructions linked to at the DYS Manual PDF link I posted originally and see if that helps:

http://www.getfpv.com/media/wysiwyg/documentation/3AxisbrushlessGim...

I do think that actually getting yaw to work is dependent on using the battery for power not the USB.

Gary McCray July 24, 2015 at 5:06pm

FYI update,

I finally had a chance to plug in and test my DSLRPros / DYS gimbal at least as far as basic stabilization with the following result.

No additional firmware programming or testing has yet taken place on my Gimbal.

With laser rangefinder attached to the Camera tray and counterbalanced for roll and pitch, when the 7.4 volt power was applied the laser rangefinder immediately leveled to horizontal and level in roll.

When the chassis was pitched and rolled the rangefinder remained level.

When the chassis was yawed, the camera remained stable and followed the yaw with a short < 2 second lag (which is what I would expect of yaw stabilization).

I think this is a good opening test for the rangefinder and if it doesn't do this I think it is safe to assume something is wrong.

And Dan, from the results you have reported above, it seems pretty likely (to me at least) there is something wrong with your Gimbal.

You will need to have a GoPro or weight simulating the GoPro in the camera mount pod so that you can achieve good static balance.

I used a 7.4 volt battery but note that on the DYS web site that their 3 Axis Gimbal is listed to work with anything from 7.4 to 25 volts.

If anyone can do so I would greatly appreciate clarification of the input voltage range of this DSLRPros version - Mike Perhaps???

Obviously 7.4 volts will work and is safe for testing, but I suspect that 11 volts (3 cell or higher might achieve faster tracking) if it is OK.

Best Regards,

Gary

Mike Knott July 16, 2015 at 8:15pm

Dan,

I'll make sure that's sent in the morning. Sometimes you need to do a 6DOF calibration on the IMU to get a good value. Usually, though, the problem is either the IMU value is off, or the motor direction isn't set up right. I've rarely had a bad gimbal rear its head during testing. We can help you through this.

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Great deal on a 3 axis gimbal with Alexmos controller

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