Wookong-M first flight

[RTRyder]

I think I found the problem...

With just the WKM on quad sitting in the same spot as MK was, powered by an RX battery and nothing else connected, RX and ESC leads completely disconnected, it took slightly over 9 minutes to no flashes so it didn't appear that peripheral RFI was causing the problem either. Being the type that likes to get to the root of the problem I kept trying...

It appears the source of the RFI is the IMU itself. Even though the GPS had 7 to 8 cm of distance to the IMU it was sitting directly overhead. I bolted the pedestal to the back of the centerplate using the longest shaft and put the GPS on top giving it 5cm of separation horizontally and an additional 4 to 5 cm vertically. Again powering the WKM with just an RX battery it went full lock in under a minute, so unless it caches the satellites it finds ala MK, it did indeed go cold start to lock in an acceptable amount of time and it appears the GPS needs to be as far away from the IMU as you can reasonably get it. That also explains why folks that used a large copper sheet under the GPS had success, it wasn't so much acting as an antenna as it was shielding the GPS from the RFI given off by the too close IMU.

Now to put all the connections back and see if it can repeat that performance with everything powered up...

Ken

 

[Gary Mortimer]

As a slight aside, when planning fixed wing UAS missions I make sure I use a tool like this

http://www.navcomtech.com/Support/Tools/satellitepredictor/main.cfm

To see just how many sats are visible at the site, you really should be flying with more than six in the sky. Multirotors are a little different as they are basically flat all the time and not rolling and obscuring the sky with a wing. A sustained turn can really cause you issues on a poor sat type of day.

I am sure the GPS uses a back up battery to store the almanac stray RF from other sources can cause all sorts of issues I bet it was pushing signal strengths down. Something joining in on 1200 or 1500mHz or a harmonic of.

 

[RTRyder]

I put it all back together making sure the GPS was as far away from the rest of the electronics as I could get it both horizontally and vertically. Started the Assistant software and reconfigured the mounting to reflect the relocated GPS, strapped on a fresh battery and headed outside.

Placing the quad in the same spot I powered it up, noted the time and stood back, went to 2 flashes in just under a minute and down to 1 flash around the 2 minute mark. At that point I lifted off in ATTI mode and let it hover around 10 feet up for a bit, in a bit less than 3 minutes it was fully locked, the only flash from the LED was the ATTI mode indication.

Set it in GPS mode and found it to be a LOT more stable than it had been previously with full lock, no doubt due to lack of interference with the GPS now that it's moved. Anyone having issues with toilet bowling in GPS mode might want to check the spacing of the GPS antenna to the rest of the electronics, moving it back and up seems to have cured mine of it. It's blowing a bit of wind out back so it was a good test time, the most it moved in GPS lock was maybe a meter in any one direction and as soon as the gust was over it would work its way back pretty close to where it started.

Took it up to about 50 feet where the wind was a bit stronger and it held as well, perhaps better, than my MKs. Brought it down to where it was about level with the top of the stockade fence and subject to buffeting and swirling gusts caught between the fence and the house, still held within 2 meters with no tendency to circle.

Another flight a bit later took a bit over 5 minutes to get to one flash so it varies somewhat but technically it's GPS usable on two flashes so usually less than 4 minutes, still not as good as the MK but much better than 10 minutes plus.

Next big test is RTH and autoland, since turning off the TX is a bit too much of a leap of faith I setup a mix using the gear switch to put the controller in failsafe mode when I turn it on. For that I'll have to go to a much larger area as it will go to a 20 meter height before it does RTH and who know what the accuracy of the GPS will be, so want to have plenty of space just in case...

Ken

 

[Bartman]

ken,
does it also have a gain type setting for gps like the mk does? i'm wondering if there's any need for the operator to adjust gps settings for different wind conditions.
thks
bart

 

[RTRyder]

ken,
does it also have a gain type setting for gps like the mk does? i'm wondering if there's any need for the operator to adjust gps settings for different wind conditions.
thks
bart

Here's what one of the DJI China folks had to say about that...

"Run the Atti gain as high as you can without oscillations. Of course, everyone is different. I only have two in the office today (Shanghai show took 4 from marketing dept). Atti gain no less than 125%, as high as 170% on the second one (480 and the 404) They are like parked car in the air with 7-10 mph wind."

I haven't yet made any changes to the out of box settings and the quad is flying amazingly well, will likely have to make changes once it goes back on the Y6. I'll find out soon, I hope, still waiting for the promised release of the firmware with Y6 mixer. I'd rather they take their time and make sure it works before releasing it, I'll keep testing things with the quad frame in the meantime.

Ken

 

[Emowillcox]

Hey Ken.. really thank you for keeping us so up to date on your experience with the DJI set up. I have been trying to follow your thread and Boris’s thread about his build using DJI. I’m getting ready to go out of town for a few days but was about to buy some new gear and was thinking about getting DJI stuff, but Robert has only responded to 1 out of 4 emails I have sent him. Big factor for me on gear at this price will be the level of support. Not sure if Boris is reading your thread here but I am curious how you guy’s experience with communicating with the DJI guys has been? What has been the best way to get in touch and have they been pretty good at getting back with support?

 

[BorisS]

of coarse I am reading this thread and pretty happy that Ken is on this, evens the road for me as someone with less experience. I wrote you an PM regarding your question.

 

[RTRyder]

Hey Ken.. really thank you for keeping us so up to date on your experience with the DJI set up. I have been trying to follow your thread and Boris’s thread about his build using DJI. I’m getting ready to go out of town for a few days but was about to buy some new gear and was thinking about getting DJI stuff, but Robert has only responded to 1 out of 4 emails I have sent him. Big factor for me on gear at this price will be the level of support. Not sure if Boris is reading your thread here but I am curious how you guy’s experience with communicating with the DJI guys has been? What has been the best way to get in touch and have they been pretty good at getting back with support?

Support has been really good so far, understand that the first shipment has just reached end users this week with more going out and Robert is a bit swamped between supporting people working out their setup and keeping the new shipments moving. There is also SidneyW that posts on RCG exclusively and he is a lot closer to DJI, as in he's in China, and has been very helpful with support as well. Once things level out it should be a lot easier to contact local folks for support, right now I think they have all they can do to keep up with the initial batches hitting the streets.

Ken

 

[Emowillcox]

HI Ken and Boris.. thanks for responding to my questions. I imagine they are pretty swamped at DJI with the first batch of Wookong going out multis. Guess i'll be patient on placing my order.

 

[RTRyder]

The Y6 is flying now. Working on getting the gains dialed in, had to make significant increases and still going. Its proving to be more stable than it was with MK flight controller using I2C converter and PWM ESC's but I'm not at all surprised by that. A better comparison would have been to use the MK BL controllers but I wasn't interested in tearing apart one of the Hexa to do that.

GPS is locking in nicely with it even farther away from the IMU and the rest of the electronics, still not nearly as quick as the MK but within acceptable time, usually around 2 minutes to get to a single flash on the LED.

I just connected the camera mount servos to the controller and did an eyeball setup, going to turn the GoPro on for the next flight. The gimbal setup is different than what I've used before so I have no clue what the end result will be for video, just have to do and see what comes outof the camera then make adjustments from there.

Ken

 

[Gunter]

Ken, you are really keeping us in suspenders here...please could you do a quick video of you flying and also altitude hold/gps. If you are struggling for time, send me the raw footage and I'll gladly edit it and upload to the relevant video sharing website

 

[Gunter]

Ignore my last message, just spotted your other post