Herky-Jerky WKM during RTH

P

PeterLester

Member
Seeking help with WKM RTH issue using firmware version 5.20.
All functions and led lights worked perfectly for many previous flights until today when all worked correctly except for RTH.
When RTH is switch activated, the MR bucks like a bronco will returning to home..... this bucking continues until the MR begins to descend over the home point..... then smoothes out well before final landing.

What changed since last 100% successful flight
X2 was briefly used for gimbal control but reversed via Futaba transmitter.
Forgot to return X2 direction to normal when I switched it back to in flight tuning via WKM Assistant.
not an issue with Manual, Attitude or GPS modes.

But now RTH is very glitchy....... not pretty!!!

Additional info:
Motors/props: NTM Series 35-30 1100kv 380 watts each using 10 x 5 Graupners and 2x3S 5000 batteries.
Basic Gains as follows:
Pitch and Roll both 190
Yaw 170
Vertical 150
Attitude Gains as follows:
Pitch and roll both 180
All gains adjustable in-flight from RC transmitter.
Anyone here have similar issues and/or know why this happens and how to fix it..?:dejection:
 
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Kilby

Kilby

Active Member
I've seen the same thing with my wookong. This happened both in RTH and with the waypoint click-n-go. I never did figure out what the problem was. While it did buck back and forth a lot, it would still stay in the air, so I gave up on trying to find the problem.
 

P

PeterLester

Member
Thank you for some good feedback.... now I have some faith that it may not get worse......

Worked through every possible RC transmitter and WKM Assistant configuration on the bench but no improvements at all on subsequent test flight....
I am hoping to re-install 5.20 firmware to see if that will clear the corrupted input data to the controller.

Seems I can jumper M5 and M6 together and reconnect WKM assistant software to the WKM which will then allow me to re-install the firmware.



Kilby said:
I've seen the same thing with my wookong. This happened both in RTH and with the waypoint click-n-go. I never did figure out what the problem was. While it did buck back and forth a lot, it would still stay in the air, so I gave up on trying to find the problem.
Click to expand...
 
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J

jip

Member
Hi PeterLester,

Me and another guy here in France have a similar problem : our MR fly perfectly in any mode (manu, atti, gps) but we have the same bucking you describe when in RTH, plus our MR will not go-home but remain hovering forever, never descending until we take control back. (yet we set it to "go-home", not "hover")
The other guy found out that if he had the gimbal OFF in the dji soft with non-default values (anything else that -1000 / 0 / 1000), then he had this problem (bucking / non descending).
But if he has either the gimbal ON or the gimbal OFF but with default values (-1000 / 0 / 1000), then his problem is gone - no more bucking and successfull go-home.

I'm with gimbal ON and yet I have this problem, so there must be another explanation.
But maybe you can give it a try, or maybe it can bring ideas ? Or maybe it's just more confusing now !!

JiP
 
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P

PeterLester

Member
I also have GCS and do not want to compromise flight safety or increase wear and tear on the MR motors etc. when the "herky-jerky" kicks in...... must solve this problem or cannot use GCS as intended......

So far there have been several solutions proposed:
a) Do not configure X2 for remote gain adjusments while flying
b) return gimbal setting to default
c) Re-install the firmware or move it back a notch

For option "c" two methods were identified:
a) Jumper M5 to M6 on WKM to enable a re-install of 5.20 firmware
a) or remove WKM Assistant software from PC, then reinstall. Then do a previous firmware update such as 5.16 and work back up to 5.20 after that

Kilby said:
I've seen the same thing with my wookong. This happened both in RTH and with the waypoint click-n-go. I never did figure out what the problem was. While it did buck back and forth a lot, it would still stay in the air, so I gave up on trying to find the problem.
Click to expand...
 

P

PeterLester

Member
Problem is solved..... thanks all for your input/help.... My MR is now functioning 100% including RTH without any bucking during the return home.....

I stepped off the forum and posted a help request to UAVProducts USA where I bought my WKM. Here is Robert Remund's response....

"You have to make sure when you switched X2 back you did not put it back on gains thus causing all the oscillations.".....

WOW.... that is what I call quality technical support service.
 

J

jip

Member
Hi PeterLester,

I'm not sure I understand that.. (actually I'm sure I don't ! language barrier I guess !)
Would you mind explaining ?
This means you can't control gains using X2 ? So it's a software bug ? I use X2 on gains and switch off my transmitter to go on failsafe, but my x2 value is the same when flying or when on failsafe, so I don't understand why th bucking (unless it's just a bug)

Or is it because you used X2 for both RTH and gains, so you had RTH with very low gain causing oscillations ?

Thanks,
JiP
 

P

PeterLester

Member
When changing back from gimbal control to gain control using X2, something can go wrong with the MR control system but only in RTH causing oscillations.
UAVProducts seems to know about this and how to fix it.
The fix is to return the Basic and Attitude gains control from X2 to INH, i.e., inhibit.
As to cause and effect..... we would have to see a detailed flowchart of the programming and/or see a copy of the source code.....which will not happen.

I have a suspicion that the previously loaded X2 gimbal values residing within the MR controller are not compatible with X2 basic and attitude gain values!
When switching back to remote gain control, it is important to first clear out the "out-of-bounds" X2 gimbal values. Otherwise the RTH nested PID loop controller is attempting to use bogus X2 values resulting in PID loop control oscillations.


Once you have your MR - RTH mode flying properly again with gains set @ inhibit, it might then be possible to re-enable RC transmitter remote gain control after reconfiguring with WKM Assitant on the bench.

jip said:
Hi PeterLester,

I'm not sure I understand that.. (actually I'm sure I don't ! language barrier I guess !)
Would you mind explaining ?
This means you can't control gains using X2 ? So it's a software bug ? I use X2 on gains and switch off my transmitter to go on failsafe, but my x2 value is the same when flying or when on failsafe, so I don't understand why th bucking (unless it's just a bug)

Or is it because you used X2 for both RTH and gains, so you had RTH with very low gain causing oscillations ?

Thanks,
JiP
Click to expand...
 
Last edited by a moderator:

J

jip

Member
Thanks a lot ! Will try and report.
So no more live gain control.. :upset:


PeterLester said:
When changing back from gimbal control to gain control using X2, something can go wrong with the MR control system but only in RTH causing oscillations.
UAVProducts seems to know about this and how to fix it.
The fix is to return the Basic and Attitude gains control from X2 to INH, i.e., inhibit.
As to cause and effect..... we would have to see a detailed flowchart of the programming and/or see a copy of the source code.....which will not happen.

It could be that there are certain parameters used in gimbal control using X2 that are out-of-bounds for RC remote gain control. And without thorough error correction routines within the firmware, it may not be possible to clear out the corrupt input data to a nested PID loop....... mere speculation ofcourse!
Click to expand...
 

P

PeterLester

Member
Once you resolve the RTH bucking issue after setting Basic and Attitude gains back to inhibit, take your MR back to the workbench and using WKM Assitant, try setting new gain parameters using X2 for RC Xmitter remote tuning control and see if RTH works without the bucking bronco effect.


jip said:
Thanks a lot ! Will try and report.
So no more live gain control.. :upset:
Click to expand...
 

J

jip

Member
Hi,

So here's the report !
I tried rth with all gains inhibited : no change - same bucking and hovering forever
I tried with gimbal OFF : perfect RTH
I tried with gimbal off and manual gains (pitch roll) on X2 : perfect RTH
So I tried playing with gimbal settings until I found the one parameter which has a consequence on RTH.
And the winner is....
Gimbal Pitch center.
Set on 0, RTH is perfect
Set on -300, rth doesn't work (only rises to 20 meters with frightening movements, doesn't come home, doesn't land)

So I kept my "gimbal center" on 0, and centered my gimbal manually - now everything is OK.


JiP
 
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Kilby

Kilby

Active Member
This is very interesting. I had my gimbal off center when I had the same issue in click-and-go way point navigation. I guess disabling the gimbal control entirely and using a brushless controller would fix that problem.

Just curious, what firmware version did you test this against? I'm still on something very old like 5.12 (if it ain't broke, I don't fix it!), but think ill need to upgrade soon due to DJIs new Bluetooth LED.
 



P

PeterLester

Member
Those that use Naza will recall that remote gain adjust can be controlled via X1 and/or X2.
But remote gain control on WKM allows X2 and/or X3 but not X1......!!!

It seems an out-of-bounds X2 value is getting into the Basic or Attitude gain control when switching from gimbal control back to remote gain.
One possibility is a negative value (signed integer) where the PID or nested PID loop controller only allows for unsigned integer input values.
I've seen that issue crop up before but with negative temperature values being reported back to a SCADA Host as 32768 etc.
 

M

modles

Nerdlinger
interesting idea but i think the results from that would be more catastrophic. All I can say is I just replaced the IMU only on mine and it was fixed.
 

B

Benchmark

Member
jip said:
Hi,

So here's the report !
I tried rth with all gains inhibited : no change - same bucking and hovering forever
I tried with gimbal OFF : perfect RTH
I tried with gimbal off and manual gains (pitch roll) on X2 : perfect RTH
So I tried playing with gimbal settings until I found the one parameter which has a consequence on RTH.
And the winner is....
Gimbal Pitch center.
Set on 0, RTH is perfect
Set on -300, rth doesn't work (only rises to 20 meters with frightening movements, doesn't come home, doesn't land)

So I kept my "gimbal center" on 0, and centered my gimbal manually - now everything is OK.


JiP
Click to expand...

Spot on mate, thanks a lot i can confirm this fix too. It fixed my jerky RTH problem exactly as described.
 

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