WKM GPS/ATT poor performance

[139 jockey]

I Have just built a SJ6 with a WKM but am having problems with it in GPS/ATT mode. I have had it hold position a few times but often it either fails to recognise that I am stick central ( I have tripple checked all settings and it seems I have it set up correctly when checking with WKM software) , so double blinks purple on the LED. Even more perplexing is that even if I do get a full GPS lock ( IE 7+ satt. so just single flashing purple LED) the aircraft will hold altitude but enter a dynamic fugoid, starting by moving in a 1-2m square but rapidly growing up to 20m. If I don't put in stick in puts to regain control I am pretty sure it will end in tears.
Has any one else had these problems please? Is it possible that it is to do with my gain settings? The SJ6 is flying pretty well in ATT mode.

 

[Michael64]

Solid blue means you have a radio communcation problem. Sounds like failsafe is activating. Did you setting the 3 position switch to get manual atti and GPS to light up blue. When switched to GPS it should be a purple like color. When connecting battery you should get an array of all lights then you will get 3 red and yellow orange over and over then it will go to 2 reds and yellow orange single than 1 red and the yellow orange than when full lock it comes than its no reds and either no lights for manual the yellow orange light for Atti or the purple looking light for GPS.

Michael64

 

[139 jockey]

Sorry, I probably wasn't very clear in my explaniation. I have all the normal lights that one would expect. If in ATT it does just as you say, yellow with 3 reds for no GPS , then 2 x reds + yellow followed by in due course by just flashing yellow in ATT once it gets 7 + satt. The led changes to flashing purple in gps mode, but often the double flash indicating that it is in gps /att but it has detected a stick input, even when I have not done so. It will go to a single purple flash if I come to a steady hover but it has to be very steady before it will enter GPS hold. That is when the crazy stuff happens with the fugoid, starts dashing about the sky like a drunk angel.
I have tripple checked the radio calibration and yes all is as it should be. I was even brave enough to try fail safe home and that worked, perfect auto land right on the numbers. It does the clever stuff OK but not the basic stop in one place thing. I might try the intelligent orientation latter today if the weather holds to see if the gps does what it should there.

 

[139 jockey]

Righto- I have found the thread about the toilet bowl effect and it appears I am suffering from it, which is a real shi#&er. I will follow all the exellent advise already there,

Rick.

 

[Michael64]

Make the mounting measurement are real close as well along with the right positive and negative values this will also cause the T-bowl issue as well.

Michael64

 

[Emowillcox]

Yeah I have not had much luck figuring out how to make those settings work on my wookong. Anyone fly in manual mode? I have tried a few times on accident and its a real hand full to fly.

 

[139 jockey]

OK- Starting to make some progress here. I remeasured the COG ( It had changed due to large lens on camera ), and re input the measurements. I also re positioned the GPS to the other side of the A/C so it is further away from the Batt. leads. I also did another compass calibration.
It took an age to aquire the satetlites ( about 8 min) but it is definetly holding position a lot better. It is still reluctant to enter GPS hold unless it is in the hover, and did enter a much smaller TB. It is blowing about 15 knots in the back yard now so it's a bit of an ask.

Does any one know how this system works, does it just use gps position( which is always changing due to the fact GPS isn't perfectly accurate) or does it use and intergrated positon solution cross referencing the GPS position with the IMU information? The accelerometers in the IMU should be able to take out even the smallest movement. I know that the helicopter I fly at work uses this system, in Auto hover it holds position with the AHARS but if you want to move position you can "BEEP" the A/C to a new gps position where the AHARS will take over the fine work again.

Rick.

 

[srbell]

Fixed my TB problem

By making sure the measurements were dead accurate. On another note, your double flash isn't idicating anthing wrong, just that one of your sticks isn't centered.... Your throttle stick lol. When you get to hover position, it will return to a single flash.

 

[Emowillcox]

Hey Jockey .. what kind of work you doing where you get to use a system that uses accelerometers in the IMU? I found when I first plug in my wookong it takes a while to find the satelites but if I do multiple flights usually the next time is pretty quick to find the satelites

 

[139 jockey]

Hey Jockey .. what kind of work you doing where you get to use a system that uses accelerometers in the IMU? I found when I first plug in my wookong it takes a while to find the satelites but if I do multiple flights usually the next time is pretty quick to find the satelites

I fly a dirty old AW 139 for my day job, but the technology is very simillar. The 139 has a AHARS ( Attitude, heading and refferance system ) which is an IMU by another name. It would be great to see WKM using all the inputs avaliable ( asuming they are not presently, I would have thought that it would have been a heap more accurate if it was ) to make this thing work much better.

Rick.

 

[139 jockey]

I just snuck in a flight before the WX turns to puss for the next few days. In calm conditions it worked almost as it should. The only glitch is that if you release the sticks with any forward speed then the A/C rolls left slightly then settles down in a decreacingly small TB. After 3-4 occolations it settles in to a solid hover.
Any one have any idea's on that?

Rick.