WKM S800 loses altitude when flying forward

[gtranquilla]

Seems to me that I read somewhere that it is possible to adjust basic and attitude gains to ensure the MR does not lose or gain altitude while flying forward, sideway, backward etc. But I can' seem to locate that info now.
I am guessing that the vertical gain will control this..... Am I correct or is there a better way?:dejection:

 

[ProPilotWannaBe]

I'll let some of the more experienced guys reply at more length. But from what I understand, if you are loosing altitude just as you are cruising (left, right, forward, back), it is more than likely not related to gains. The gains control the responsiveness of the system to the pilot's commands, or the ending of those commands.
I have read three causes for loss of altitude:
1) Imbalance of the aircraft... i.e. too much left/right weight, or, in your case forward or aft weight.
2) Improper configuration of the WKM to your transmitter... i.e. controls in detent (centered) are not registered with the WKM as exactly centered. I read that you have to ensure that when running your calibration, the controls need to end at 50 to register the detent position.
3) There is a known issue with the IMU. This is the one that has a lot of operators very upset right now because there appears to be a design flaw in the IMU, and/or its installation position on the S800. For that, DJI has issued a new V2 IMU that will become available shortly for all users, but there is an upgrade cost (which is what is making a lot of current users upset... why do we have to pay for a fix to a flaw in the design).
Like I said, I hope some of the more experienced operators will chime in, but the above is what I have experienced, and/or read as causes for loss of altitude.

 

[Dewster]

My Y6 does the same. I have the WKM. Fast forward flight results in loss of altitude. I didn't have that issue on my Flat Hexa with the same WKM IMU module on an earlier firmware. I guess at some point the angle of attack becomes too steep resulting in a loss of altitude. And I'll never admit to being an expert. That's why I come here so often.... For good intel.

 

[PeterLester]

Well.... if all else fails.... read the manual....... and it says....

"You use two methods to judge if the Vertical gain is good enough: 1) The multi-rotor can lock the altitude when the throttle stick is at center position; 2) The change of altitude is small during the flight along a route. You can increase the gain slowly (10% each time) until the vibration emerges along the vertical direction or the reaction of throttle stick is too sensitive, then decrease 20% of the gain. Now it is a suitable Vertical gain."

And since the WKM worked perfectly on many previous flights on my modified F550..... I suspect some vertical gain adjustment might help..... will try it tomorrow.

Regarding possible design flaws in the IMU.... not likely..... it is IMHO simply a matter of the original control algorithms not being developed to handle MR AUWs beyond the original design specifications..... they didn't see the future with respect to much heavier than anticipated AUWs.

 

[Dewster]

Well.... if all else fails.... read the manual....... and it says....

"You use two methods to judge if the Vertical gain is good enough: 1) The multi-rotor can lock the altitude when the throttle stick is at center position; 2) The change of altitude is small during the flight along a route. You can increase the gain slowly (10% each time) until the vibration emerges along the vertical direction or the reaction of throttle stick is too sensitive, then decrease 20% of the gain. Now it is a suitable Vertical gain."

And since the WKM worked perfectly on many previous flights on my modified F550..... I suspect some vertical gain adjustment might help..... will try it tomorrow.

Regarding possible design flaws in the IMU.... not likely..... it is IMHO simply a matter of the original control algorithms not being developed to handle MR AUWs beyond the original design specifications..... they didn't see the future with respect to much heavier than anticipated AUWs.

Thank you! I remember reading that now. Lol.

 

[Lanzar]

If you will not be able to solve this then you need to upgrade to new IMU v2.

 

[MombasaFlash]

... Regarding possible design flaws in the IMU.... not likely..... it is IMHO simply a matter of the original control algorithms not being developed to handle MR AUWs beyond the original design specifications..... they didn't see the future with respect to much heavier than anticipated AUWs.

Maybe, but ... with an all-DJI rig of S800/WKM/Z15G plus GH2 there is little excuse for DJI (or anyone else) to suggest that this configuration is outside original AUW specs. It is all their gear and sold as a standard configuration. As I remember it the S800 was the first MR released, i.e. before the Flamewheels etc., so your argument in support of DJI does not hold.

DJI is in the 'Apple' position of supplying the software to drive the hardware. We are not dealing with third-party elements and as such it should all operate correctly. I stick by my original claim that they screwed up the design of the ESC's ... the GPS ... the iOSD ... the IMU ... the booms ... nothing much left to fix after that lot - unless the V2's are also bad.

 

[saidquad]

DJI is in the 'Apple' position of supplying the software to drive the hardware. We are not dealing with third-party elements and as such it should all operate correctly. I stick by my original claim that they screwed up the design of the ESC's ... the GPS ... the iOSD ... the IMU ... the booms ... nothing much left to fix after that lot - unless the V2's are also bad.

Center plate should be upgraded because on the center plate there is a space with an arrow on it especially designed for IMU location. Now that IMU is gone and IMU V2 is going to be placed somewhere on the landing gear the original space of the IMU is useless. However this especial space of the IMU on the center plate is a good sign that DJI had planned to use WKM and the IMU V1 as the control unit for S800. DJI did also announce that Zen is especially designed to work in conjunction with WKM and S800. And S800 was indeed designed to properly work when the weight was limited to 7kg. I really wonder if DJI QC team (if there really exist such a team in DJI) did test fly a 7kg S800 with WKM before they write the hand book of S800.

 

[PeterLester]

This is how I understand the need for recent changes to IMU placement......

Many pilots doing Aerial video work with DJI and other MR products had to get a 2nd IMU dedicated and installed with the video camera/gimbal system to get professional quality results.
DJI's approach has been to incorporate gimbal control into the single IMU. But it's effectiveness was limited because it's primary function was MR control. Hence it was placed on the MR airframe.
Subsequently they realized that the optimum locations for a single IMU is with the camera gimbal/landing gear assembly.
And there is little to no adverse impact on MR control despite the vibration isolation between the two.

 

[PeterLester]

Adjusted vertical gains and it now works perfectly!!!! Never a doubt in my mind re: the quality of DJI controllers.