S800 oscillating flip

[Javajack]

Hey gang, I just joined tonight to get a little assistance. I've owned an S800 for several months and we have done some great aerial photography. I've had a couple of unfortunate oscillating flips when coming home, but this has only happened in the past few weeks and I'm looking for some assistance. I've watched every video out there pertaining to the FOD (Flip of Death) but my issue seems to be different and I haven't seen any crashes that look like mine. I'm posting my crash today for awhile to get some feedback, but basically when returning home on first low battery warning my S800 has become unstable and then begins oscillating, swinging from one side to the other until it can no longer stay in the air and plunges to the ground. In the video you will see the aircraft come into the camera, swinging back and forth while the camera gimbal stays perfectly locked. I'd appreciate any help with this.

For background we are running the reinforced EVO arms. We have the anti-vibration isolation kit which places cushions between the upper assembly of arms, isolating vibration and keeping it from getting to the gimbal and IMU. The compass is mounted securely with a mounting bracket instead of double-sided tape as we thought the antenna may have broken free the last time this happened. We are on the update firmware. I can't think of anything else. Oh wind was about 10km so not too high but I was returning into the wind after an approach to this butte. Here's the link to our crash. http://www.youtube.com/watch?v=r6lZgNMpmGY&feature=youtu.be

Oh ya here's a few great moments so my post has balance. http://javapost.ca/index.php?pageid=Our-Work&videoid=167

 

[ChrisViperM]

One question: Did you replace the re-inforced arms yourself .... ???

When I replaced my arm and did the soldering, I realized that the metal spots where the wires gets soldered on is thin like a hair....If soldered to hot, it could be that the soldering joint becomes loose together with that metal....and you wont even see it just by looking at it. Due to vibrations it could come loose only after a while and cause all sorts of malfuncions with ESC's and motors.


Chris

 

[Javajack]

One question: Did you replace the re-inforced arms yourself .... ???

When I replaced my arm and did the soldering, I realized that the metal spots where the wires gets soldered on is thin like a hair....If soldered to hot, it could be that the soldering joint becomes loose together with that metal....and you wont even see it just by looking at it. Due to vibrations it could come loose only after a while and cause all sorts of malfuncions with ESC's and motors.


Chris

We did replace the arms ourselves but it was done by my technician, who is a qualified radio/tv tech. He mentioned how difficult these wires were to solder and about the possibility of over heating etc, but knowing him they were done correctly.

I woke up thinking about this more and think this may have been pilot error, as much as I hate to admit it. I had the gimbal in manual mode instead of horizontal lock, which is how I fly when I pilot and shoot video alone. I have a monitor on my controller so I can see my image and so does the cameraman. This day I was flying alone with no cameraman and when I decided to come home I had yawed the craft around an undetermined amount. When I pulled the pitch control towards me I wasn't sure if the craft was flying away or towards me and it was a fair distance away, so difficult to see markers or LED. I yawed to where I thought I should be, but the camera was locked to a spot on the horizon so I could see landing gear travel through the shot. I used this to help get my bearings then pitched one way and then the other until I could see I was moving home. I think the change of direction may have set up an oscillation because the camera, wanting to stay balanced would suddenly tilt to correct for the attitude change in the craft and then tilt back again when the direction changed. This may have set up a deadly oscillation, aircraft pitching, camera gimbal pitching to compensate.

If this is the case what is the best escape. You only have 5 seconds from when this oscillation happens before its really out of control and on the ground in a pile. Hit manual and try to fly out of it? At the distance I'm not sure I could have told enough about copter attitude. The other thing is to never get in this situation, suddenly changing direction, I guess.

Jack

 

[Electro 2]

When the video begins, the aircraft is already in trouble with motors surging and the like. I'd be more interested in what happened *before* the video starts for diagnostics. One "dirty trick" I'm familiar with is to monitor the *audio* from your FPV link with an earbud when flying, if you hear motors producing sounds other than the usual nearly-syncronous, organized, drone, some kind of issue is afoot.

 

[Teamflail]

Hey Jack, I have had this happen twice now with, luckily, minimum damage. Were you in GPS mode making any large direction or power changes? Both times it happened to me I was in GPS mode somewhat close to the ground and making some dramatic changes from the TX. Not really much time to figure out how to get out of the oscillations before crashing.

My thinking is it might be relating to some type of interference with the GPS and then my inputs don't help the issue. If it happens again I have an action plan to try and immediately switch to Alti hold mode in the hopes I can avoid the crash. Let us hope we can avoid the FOD in the future.

 

[Javajack]

Thanks for your post. Yes, it sounds like you are experiencing the same thing as me. Unfortunately I was at a fairly high altitude so damage was significant. Just so you know, DJI is now looking into this. We have offloaded our flight logs from the isod and they have them. We also have a couple of theories as to what is going on here and hope you can respond to this. If you look at my video post above you'll see that I've chased bikes and even vehicles, inputting great speed and direction changes without issue. This oscillation incident starting happening about the time we purchased the isolation kit for the Wookong IMU that moves it back onto the H frame. We programmed in the new offset from the antenna and everything should have been fine and in fact GPS hold was improved because the vibration was reduced. Unfortunately we've now suffered two oscillation crashes in the past two weeks in this configuration, so we'll see what DJI has to say.

At the time of the oscillation, yes I was inputting position changes. I had been moving towards a butte or hill which had people on top. I didn't want to get any closer so increased altitude and began coming home. I was a fair distance away and had yawed the craft to the point that I wasn't sure of it's attitude so I pushed fairly hard on the roll to see which direction it would correct. I think this change in roll, one direction then the other may have initiated the oscillation as it may have in your case, too. The thing is that I could easily get away with these moves a few weeks ago. Are you running the anti-vibration kit?

When my first oscillation crash happened I was at altitude and had a few seconds to figure it out. I tried to first power up and fly out of it in GPS but this didn't help so I switched to Attitude mode, assuming that would correct things, but it didn't. I really think a person has to go full manual to get out of this situation. I've been afraid to attempt a full manual flight to this point fearing it may be very hard to control. It's the not knowing that' tough to get past.

 

[Teamflail]

Thanks for the information Jake. I do not have any type of anti-vibration kit. Hope to hear what DJI replies back with. Was going to ask about the firmware but looks like you are on the latest. It definitely has me a bit gun shy so I may start flying in Alti hold mode for the time being unless I am unsure of direction of travel, etc. Sorry to hear you took some significant damage. Only one broken arm and landing strut for me so been lucky.

 

[Javajack]

Ya, this has cost me like $5,000 for the crashes and the repairs, including labour and parts. I'll let you know what transpires.

 

[Teamflail]

Found this video of a S800 flipping and crashing. It happened faster than with my experience or, from what I can tell, yours but it looks familiar. Looking to see if the compass module I have needs to be re-flashed.

http://www.youtube.com/watch?feature=player_embedded&v=RqhwSX6VXf4

http://www.suasnews.com/2012/10/193...-bug-causing-spontaneous-s800-system-failure/

 

[Electro 2]

Found this video of a S800 flipping and crashing. It happened faster than with my experience or, from what I can tell, yours but it looks familiar. Looking to see if the compass module I have needs to be re-flashed.

http://www.youtube.com/watch?feature=player_embedded&v=RqhwSX6VXf4

http://www.suasnews.com/2012/10/193...-bug-causing-spontaneous-s800-system-failure/

Actually, both of these items feature the known Southern hemisphere GPS code error that DJI nailed down and dealt with in October of 2012, nothing to do with compass. This resluted in a new GPS/compass product and firmware at that time, and is pretty much a solved thing to the best of my knowedge. I'll assume "Java Jack" is in Canada, (URL), and that is very much in the Northern hemisphere.

 

[Javajack]

Yes, we're in Saskatchewan in Canada. Would our location make a difference to our GPS possibly. Don't know if that's what you're getting at.

 

[cbpagent72]

What frequency is your fpv setup?

Sent from my SPH-L720 using Tapatalk 2

 

[Teamflail]

Hey Jack just wanted to see if you had any type of update from the DJI guys. So gun shy about flying mine but I am believing my issue relates to the vibrations of the hex. Going to re-balance everything and look at mounting the IMU on some sort of dampening material. Hopefully that does not open up a whole new can of worms.

 

[Javajack]

Yes, i have a huge update and it would be good for lots of folks to know. We sent off our flight logs to DSLR Pros in Florida where we purchased the whole system. They came back to us with a log print out that showed where the oscillation began. They told us that our gains were set too high and yet we had never moved them since our copter was originally assembled. There was very little documentation and we are now getting much better support through forums and through Bradatech in Canada, where they seem to know what's really going on. Here's what the Wookong manual suggests and also what Bradatech suggests. Keep reading after for the rest of my report. The values listed in the Wookong manual are:

Basic: 200, 200, 195, 190
Atti: 190, 190

With gimbal and camera:

Basic: 240, 240, 200, 200
Atti: 220, 220

Bradatech replied that the gain settings would be the same for both the v1 and the v2 IMU. Users of the aircraft have provided these settings which seem to be more inline with DJI's specs and have been confirmed by Bradatech technical support:

Basic: 220, 220, 180, 180
Atti: 200, 200

Now, some of our gains were as high as 400 and we don't know why. As I say we've never reset since an initial set-up with DSLR Pros service via a phone call. There was never anything on paper or in an email just a phone conversation to set these. Did our crashes causes changes or were these the original gains, it's hard to tell at this point.

Moving forward, we decided to buy a complete new Wookong system doing the upgrade to the v2 IMU on Bradatechs advice. We could have done the IMU upgrade only for $240 to v2 but we wanted to keep an RMA open on our flight control system as we are now looking for some sort of compensation from DJI. We have poured at least $5,000 into repairing our system, everything from new arms, motors, gimbal support, landing gear, h frame, etc. These big crashes can get expensive.

Anyway, since receiving the new Wookong system and installing the machine has never flown better. I'd strongly suggest to anyone reading this to upgrade to at least the V2 IMU. It's less susceptible to vibration plus other improvements in control. Since installing the new Wookong system we no longer have the power landing gear collapsing when we plug in a new copter battery. DJI wanted this returned on an RMA to assess the landing gear problem but it had nothing to do with the landing gear and everything to do with the Wookong. This problem existed from the first time we powered up the copter, even before flying it.

We no longer have oscillation or crashes after several days of operation, the camera is always level, failsafe now actually works instead of crashing the copter, POI and Home always work now instead of intermittently. Obviously we had a bad flight control system. It's been returned and we haven't had word on what they might do for us. We felt it was best to move forward with a new flight controller as we were getting more concerned about public safety. We have a 2 million dollar insurance premium but we do not want to go out and kill someone with a copter that randomly crashes. I'm sure you can appreciate.

Will let you know where this all goes in the next week or so.

 

[Teamflail]

Thanks for the info. Jack! Much appreciated. Looks like my gains are the standard per the manual:

Basic: 200, 200, 195, 190
Atti: 190, 190

I might try to modify them slightly and see if that helps. I really do think the vibration is causing the IMU to go haywire.

Question, did DJI give you the offer to upgrade to the v2 version or was that through Bradatechs? Really would like to upgrade as it seems to take care of the issues we have all been seeing.

Thanks again for the information!

 

[Javajack]

That was Bradatechs idea. DSLR Pros told us the V2 IMU was only meant for heavier craft in excess of 7KG, I believe and Bradatech said that was partially true but that the V2 IMU had been designed to control the problems with vibration. We've had already moved our IMU back onto the H frame when adding the anti-vibration kit but I think our IMU was damaged or defective even before we did this. Replacing it with V2 has improved everything. I mean why would the landing gear drop every time a new battery was plugged in? We had to hold the copter so it wouldn't collapse onto the camera and gimble everytime or just unplug the landing gear. Installing the V2 IMU got rid of this issue completely, nothing to do with vibration, but obviously a lot to do with the old IMU.

 

[Teamflail]

Yeah, the landing gear issue is a weird one for sure. I am worried that possibly my unit might have been damaged during my worst crash where I lost two arms and 2 props. No way really to tell unless you fly it. Sigh... Might try to isolate the IMU in the mean time with some damping. Just hard when my heart stops beating every time the little guy takes off!

Thanks again for the info.

 

[Javajack]

I know how you feel and it's hard to know until you fly or just plain replace it. Consider the $240 upgrade to V2 IMU. You do an RMA on your current one and upgrade to the new unit.

 

[Mike Toy]

Did you ever figure out what might have caused the oscillations? Although your video link seems to have gone it sounds very similar to what happened to me last week. S-800 with A2 controller, suddenly began to swing violently from side to side. It was pretty high when it started and may have been hit by gusts coming off a nearby ridge but other than that I haven't a clue. Luckily we managed to get it back - put in full throttle at about 30ft above ground and it stabilised itself and went back to 'normal'. But a worrying experience which I'd like to get to the bottom of. Have done about 30 or so flights with it and have seen nothing like this before. Any ideas would be most welcome….

 

[Javajack]

Mike:

We never did figure out the problem other than our S800 was totally worn out. The motors started sounding awful, we began having power management issues, where the OSD reported batteries going from 25.3 volts to 22 almost immediately after lift off, reducing flying times to about 2 minutes, down from 10 or 11. We began having so many problems, constant yawing during flight, too, we finally replaced the copter. We use it professionally and it just wasn't safe to fly anymore except in wide open spaces. We actually fly at the airport as one of our contracts and there was no way I was flying the unit at the airport again, so we found a replacement quite inexpensive, as the S800 is discontinued. We were going to buy an S1000, but we have so many spare parts for the S800 we decided to get another one and this one flies like old times. Interesting what you say about the A2. Our new S800 came with an A2 and I hated it and went back to the Wookong. One of my first flights it just took off when I was coming in for a landing. I think it was headed back to China. I got out of GPS mode into Atti and flew it home that way. This happened again, even after multiple antenna recalibrations and we put the A2 on the shelf and purchased a Wookong and everything went back to normal.