Another LOS video, recently done, love this one
Just a short Blog on this build, it's been a pleasure to build the kit, and i think i might just get another, maybe even the new Trikopta.
Specs so far
1 x Multiwiicopter Scarab 12
4 x Carbon Bird 750kv motors
4 x Rc Timer 30amp ESC
1 x Arducopter Power Distribution Board
1 x Castle Creations 10amp External BEC
4 x MPI 10 x 4.5 SF Props
1 x Spektrum AR7000 Rx-er
1 x Ardupilot Mega Board with barometer and gps
1 x Thunderpower 45c 3s 2250 Lipo
A quick word on prop balancing, i never used the normal method of removing material from the heavier blade or hub to balance, i chose to add weight to the lighter blade to equal the heavy one, as well as adding weight to the lighter side of the hub to equal the heavy one. A principal that i use on RC Helis, as you never remove material from any of the blades.
I used clear nail varnish for this, as it has proved to be very durable and weather resistant over the years of using nail varnish.
Video of the maiden flight above, lots of PID tuning left to do.
Pics of build in my Album under
http://www.diydrones.com/photo/albums/multiwii-copter-scarab-12-build
Just uploaded another video with the most stable PID's i can get at the moment.
This is the link
This is a pic of the latest PID's
http://diydrones.com/photo/fairly-stable-pid-s?context=album&albumId=705844%3AAlbum%3A544452
My biggest problem is trying to weed out the slight oscillations and keep the quad stable without it being sluggish. The rate roll and pitch are down as far as i can seem to get it without losing stability, as well as the stabilize roll and pitch. However it seems very twitchy to control, and i have about -50 exponential to try and smooth it out on both aileron and elevator.
It's tricky this PID tuning.
Any pointers from anyone out there in multicopter land.
Danny
September 9th 2011 Update
A Short LOS AV clip
https://www.youtube.com/watch?v=l7xceHKebjA&feature=player_embedded
Comments
wow , i did not know this ! .. Thank you so much :) so , do you think i can drop a gopro onto that baby and be all ready to have it film me ski? you may have just spent my next paycheck for me :) lol
Kevin: ArduCopter already has follow-me mode and the rest. $860 RTF.
hi guys ,
I am very new , trying to figure out what to spend my money on ... my end goal would be to take my drone with me skiing and have it "follow me" I have seen the very expensive Mikro copters do this , but I like the scarab frame and I am on a budget so not able to drop 20k into this :) .. Would I be able to have the following features by using a scab octo kit and using Ardupilot Mega Board in stead of the PARIS board ...
Gps Hover( keep itself steady even in the wind)
GPS return to base ( in case one engine fails , battery low or Signal is lost it should go up to a good alt , then head to start point , and slowly land by itself )
POV camera in addition to a GoPro V2 ,
goggles to see POV .. Ground station
And final feature I would like is "follow me " I have a gps on my helmet , then camera follows me while I ski .
So are these things possible ? I would love for it to be .. I already fly the Scarab stealth Armour with a paris board and no longer crash , so now I want to go a bit more advanced , but have no idea where to drop my $$ lol
Ok i finally figured out the excessive trim issue, it seems one of the ESC's had a different firmware loaded on it from the other three identical ESC's. So a change of all 4 ESC's was done and the excessive trim issue has gone away, along with the slight oscillations i was getting during flights. Apparently it can be an issue were manufactures of ESC's can change their firmwares without notification or marking the fact.
One other thing i am still trying to work out, is my trim issue.
I have excessive right aileron trim and back elevator, which i've had to try and cancel out using subtrim! Seems to be working without a problem as i was not sure you could use subtrim on a quad, but i can't work out why i need so much trim!
The quad is balanced out correctly, nothing is bent, motors have the 5 degrees of pitch as per the build instructions, and i even when put them back to being straight just to see if it would change anything i still have this excessive trim.
Used to traditional rc heli's and i know if your c of g is off it causes trim issues, but like i say c of g is spot on.
Driving me a little crazy
My biggest problem at the moment is trying to weed out the slight oscillations and keep the quad stable without it being sluggish. The rate roll and pitch are down as far as i can seem to get it without losing stability, as well as the stabilize roll and pitch. However it seems very twitchy to control, and i have about -50 exponential to try and smooth it out on both aileron and elevator.
Not sure which way to go now, maybe come down more on my Stabilize Roll and Pitch _P! but how much do you come down?
Hi Chrs, just touching back on this excessive trim, i have actually straightened all motors, checked for any bent arms and all is running true, however i still have full right aileron trim on, which is still not enough as i have to compensate by flying with some right aileron input. Not sure why it is so much trim, can you trim this out with sub trim on the aileron channel?
Danny
Ah ha, interesting as this frame is meant to have the motors offset by 5 degrees, number 3 and 4 clockwise and number 1 and 2 counter clockwise. And i've done that on all, maybe one or two are more than 5 degrees hence the excessive trim.
I did question the maker of the Scarab and he stated that the offset is for vectored thrust component, which can be used with the round booms.
Hi Chris, just an update, i stripped down the quad today, installed the correct ESC re-build it and went testing.
100 % improvement as you had stated it would be the ESC. So i spent a good few hours doing PID tuning, and i got a fantastic result of keeping it stable with only slight oscillations now and then, and in wind, still some work to do i think.
I had an awesome day to be honest, i actually skipped out of going to the flying field and flying my helis with the guys today, yikes i will get cursed out.
One final question for you though, i did find my aileron trim was right over to my right maxed out, my elevator was acceptable with about 5 clicks aft, but the aileron trim really had me puzzled. The quad is balanced out nicely and even if i try and shift the Lipo over to the opposite side to counter act the excessive trim, this had no real effect. The APM is just a tad off center horizontally on the frame, but we are talking about 3 - 5mm at most so i would not of that that would be the problem.
Is there a know reason for this kind of situation with the trim?
Dmac
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