DJI, SBUS, and 8 motors?????

[Bartman]

I'm familiar with the wide grins people seem to display when they get their WK-M heli's flying for the first time and I'm familiar with the "Look Ma, no soldering iron!" exclamations that come with the DJI decision but how does one make the 6 motor outputs function in an Oktokopter and what exactly does Futaba's SBUS have that others don't?
Can someone please explain it for me?
Thanks,
Bart

 

[jffry7]

Well I am no expert but I am running futaba R6203 sbus X8 quad. And I dont know if I understood your question correctly, but here goes. Basically the SBUS free up the input of the WK-M allowing you to make it as output for servo/gimbal while the F1 F2 to be converted to motor output making it 6 + F1 F2 8 motors. So one servo lead from RX to WK-M / 6 motor + F1 F2 / T & R (gimbal)

Or did I completely misunderstood your question?

 

[quadcopters]

As Jffry said its similar to the Mk with Jeti as only needs one output from the receiver to WKM but will still give out all the channels .
And frees up the Camera gimble ports which would be used if you did not have S-BUS with a OCTO set up.

Geoff

 

[Sebas600]

I have the S-bus because on the octo I can still use gimbal stabilization. and S-bus gives faster response according to the salesman...
And only one wire to the FC

(same as above)

 

[mbsteed]

I have ordered one of these for the reasons cited above:

http://www.snhobbies.com/product_info.php?products_id=3610

Personally I think it is a bit of poor design to assume a person will use the s-bus if they want an octo configuration.

 

[redridinghood]

Just a FYI DJI wkm provides no redundancy in case of a lost prop or motor on a flat eight. At least not in my case.
I was hovering a few meters of the ground when a bug hit my jxf 14x4.
Wkm made no compensation for the missing prop.
Was in gps mode. I managed to land with no damage, but I now question the need for an octocopter with this controller.

 

[DucktileMedia]

Ah hell, are you serious? I have a hard time believing that the FC isn't ALWAYS trying to compensate. Isnt the whole idea of the controller to compensate? My big question was what happens on a flat 6? I watched a video of a guy on here who tried it and the opposite motor gets turned off so it runs as a quad. but I dont remember if that was a DJI or not. Either way I would be seriously disappointed if that were the case.

 

[mbsteed]

I now question the need for an octocopter with this controller.

I went octo with that assumption - that it would give me that kind of redundancy. When you say no compensation, what do you mean? If one motor or prop goes it means you have 7 left to keep a camera from falling out of the sky. I agree with IrisAerial, the controller would have to compensate because that is what it is testing for - is it not? Perhaps you didn't see it trying to compensate because it was close to the ground. You were able to land without any damage - that might not be said if you were down to 5 motors in a hexa configuration. ...or perhaps I am just trying to justify the extra expense of an octo I have invested in.

 

[Bartman]

if an Okto loses a motor and the craft remains level then it must be compensating for the imbalance otherwise it would demonstrate its imbalance by flipping over or listing to one side. you can't draw a force diagram with seven vertical vectors assymetrically placed around a circle without having a rotation (moment) introduced
correct me if I'm wrong please

 

[RTRyder]

I managed to land with no damage...

Then it worked. If you had been flying a flat hex you would have been picking up the pieces, or at the very least repairing some amount of damage, the hex would have flipped instantly on the loss of a motor/prop... DAMHIK...

Ken

 

[redridinghood]

Then it worked. If you had been flying a flat hex you would have been picking up the pieces, or at the very least repairing some amount of damage, the hex would have flipped instantly on the loss of a motor/prop... DAMHIK...

Ken

I saw no compensation for the lost prop. The craft survived because it landed in a thick 2 meter bush seperating my house from the street.
In the few seconds before crash the craft was unflyable, with a mind of it's own launching towards the lost prop direction.
I tried a test liftof with seven props and it was fly able.

 

[mbsteed]

That does indeed sound like the ship did not compensate. Someone else reported a similar phenomena - that is two now saying the same - that is distressing.

 

[Bartman]

the good news is it was free! :highly_amused::highly_amused:

just kidding.

 

[mbsteed]

Yes, The FC for me was free so no complaints there and everything I have read on the DJI suggests really good results - which makes me hopeful. However, the free flight controller comes at a price because I have chosen to make a new build around it with relatively expensive equipment on board, so that is the distressing part. I am still psyched and look forward to my WKM build.

 

[Bartman]

Marlo,
It should work out very nicely and consider it money in the bank. I'd think you could get your money back in a sale at any time once it's flying.
Bart

 

[Sebas600]

Just a FYI DJI wkm provides no redundancy in case of a lost prop or motor on a flat eight. At least not in my case.
I was hovering a few meters of the ground when a bug hit my jxf 14x4.
Wkm made no compensation for the missing prop.
Was in gps mode. I managed to land with no damage, but I now question the need for an octocopter with this controller.

Yes same here no redundancy at all. crashed, broken arm.

 

[Bartman]

that's bizarre and it doesn't jive at all with my understanding of these things as just a bunch of mindless control loops trying to obey the master flight controller. if it loses a prop why wouldn't it recognize the imbalance for what it is and try to correct it? it's as if it's blind to the malfunction.

 

[crcr]

This thread is close to a year old, has DJI done anything to fix this issue?

 

[Sebas600]

nope.

 

[BorisS]

in case of a hex a yes:

whats going on with octos no clue. But for sure they don't state that there is a specific routine for octos