I have just bought the ArduPilot Mega 2560 Full Kit... plus the Triple Axis Magnetometer HMC5883L. I should have it built over the weekend.. then i'm off to a my mates machine shop, and i'll make the splitter plate for the lower frame onto which i am going to fit the Ardupilot. the magnetometer i'll put on the tail as suggested. I am going to use my X-cell Razor 600E. For those that dont know its around the 50 size nitro heli.

Do i need to buy any other sensors i.e. the Sonar... i can fly a helicopter all day long but this is my first time flying one with stabilisation so any tips would be gratefully appreciated.

If this works well then i am going to try and use it on my x-cell gasser. i can get up to 20 minute flights with this. But i think for the time being a battery 600 is the way to go.

i'll post some pictures when i have it all together.



Setup Instructions

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     I tried "simple" mode for the first time today.  For those who aren't aware, simple mode is a mode in which heli's yaw is used to translate the roll/pitch commands so they're relative to the pilot's point of view.  Hard to explain but basically pitching forward makes the heli go away from you no matter which way it's actually facing.  Pushin the roll control right means the heli will cuts across in front of you from left to right.


     Before flying in simple mode it's important to 'arm' the motors.  Throttle all the way down, yaw fully right for 2 seconds.  This reset the barometer and also locks in the direction required for Simple mode.  Also note that the heli needs to stay basically in front of you for the controls to remain natural.  Also try the control while the heli is on the ground facing in various directions to ensure it's working ok.


     You can set-up simple mode in combination with any other mode..in the CLI, setup, modes menu you'll see it appears off on the right..I think pushing the yaw left switches it on/off for the mode.

Getting close to actually buying one so I can join the fun.  Not sure what to do with the old Flymentor... 

So, should I definitely get the magnetometer and sonar right from the get-go?  Which sonar, there are a number to choose from.


I think my first order of business will be to work on the tail stabilization, since I don't want to buy a stand alone gyro.  I'll set the heli up on a lazy-susan while I sort it out.  As I understand it, this hasn't really been sorted, so that can be my contribution?  Of course, I'm still probably a few weeks away from getting up and running, so maybe it'll be done by then.


Now, to try and figure out how the Arduino programming code works.  :eek:

I was reading something about this mode in one of the other forums, and I'd like clarification on something if you don't mind.  As I understand it from what I read, this mode only works with one orientation?  The other poster was saying that if you fly the heli behind where you are standing, the controls will be reversed, even if you turn yourself around. 


Also wondering, is there a feed-forward function in the code which will automatically increase tail rotor thrust with collective pitch increases?  You know the way you used to mix a little collective into your tail rotor control in a computer radio when flying a rate gyro?  It prevents the gyro from having to respond to a yaw caused by a suddenly increasing collective.


     I would definitely go for the mag, sonar and GPS right from the beginning.


     As for the sonar, the "0"s are the best because they have the widest and longest beam.  Personally I would buy the XL-EZL0 (10m range) or maybe the  XL-EZ0 (7m).  Both of these are significantly better range than the LV0 (4m range?).


     Also if you are using a Trex450, you can find a sonar mount and gps mount in my store on shapeways.com (there's no mark-up from me on these by the way),


     Getting yaw working would be a huge contribution and I guarantee it won't be done by anyone else witin a few weeks.  At first some might think it should be easy-ish but it's really not.  Sure you can get it to basically hold it's yaw with a PID controller under calm situations but can you make it deal with the pilot (or autopilot) suddenly increasing the collective pitch which leads to a sudden rotational force on the yaw axis?  A lazy susan (a spinning disc?) is what I've used as well to test.

One more thing, if you have a trex, the carbon fibre mounting plates have been manufactured and sent off to 3d robotics so they should appear in the diydrones store in the near-ish future (a couple of weeks maybe?).  please PM me if you can't wait that long.

can this be used in all model/size of trex?

Re your simple mode question, "yes"...the controls will be reversed if the heli flies behind you.  The code only use the magnetometer, it doesn't use the GPS so it has no way to know if it's infront or behind you.  I've thought of what you're getting at...it would be interesting to make the control work in circles..so for example pushing the roll control right would make the heli circle you in a clockwise direction.


Still, simple mode is quite handy especially if something goes wrong while the heli/quad is a long way away from you and it's hard to see which way it's facing.  just pull back on the pitch and it'll start coming back to you (assuming it hasn't flown behind you).


There is no "feed forward" for yaw (or anything else) yet.  If added it should be added to the 'move_swashplate' function in heli.pde.  I actually did add something like this temporarily to the arducopterNG code (precursor to ACM) and it certainly helped but still didn't let me remove the external tail gyro so I took it out.  I think you're right thought that you need something like this if we're to remove the external gyro...i think I just gave up a little too soon.

I can guarantee that it will fit an original trex 450 and an HK450 (hobby king clone).  I'm less sure about other clones but I suspect it will work.  If you think the original trex450 landing gear would fit on your clone, then the mounting plates should work for you too.


One way to check would be to see if the mounting holes for your landing gear are approximately 4.2cm apart (width wise) and 10.7cm apart lengthwise.



Yes - I agree to have the heli flying in a circle around you when you give left/right aileron is a very good idea. I would love to test that simple mode.


Hmmm.... I just purchased some items from the store yesterday.... would be nice to have the mounting plates in the same order - but it seems I also has to order a sonar so the next order might not be that far away :-)


I have a note on the HK450 part list on the wiki... as mentioned in the comments area below the flybarless page on the hobbyking site, the cheap flybarless head has a non standard ball size for the links.... so you have to remove 4 balls on the swash to mount the 4 balls included in the kit to fix the anti rotating stabilizer (the two head control links kan be fixed by mount the HK/align ball-links instead on the control rod).


I did not manage to loose my screws on the swash, so I had to take the flybarless head off - and mount a modified flybarless head described by this link http://www.skookumrobotics.com/downloads/How_to_Trex450_for_SK360.zip


This flies great with the align 3g - so the next project is to test it with ACM. I hope the default PID values will be ok - will report back when tested.



I'm confused about this mode.  When the heli is in front of you, and you push the cyclic "up", how does it know which direction is "away" from the pilot?  I assumed it was looking at a vector between "home" and the current position.  "Up" on the cyclic would command a movement along that vector.  Back would command a movement backwards on that vector, and either side would make it move perpendicular to that vector.


I'm confused about what the problem is when the heli gets behind you.  You turn your body around 180°, is it not the case that pushing "up" would again move the heli away from the LZ?


If that's not how it works, that is how I think it should work.  The only problem left is that, assuming the pilot isn't actually standing ON the home position, but 20+ feet away, there's a 20 foot zone where the controls are confused.  Say you are facing due north.  The "home" position is 20 feet north of you, and the heli is currently flying 200 feet due north of "home".  You pull back on the cyclic, and the heli comes back towards home.  When it reaches home, it's due-south momentum would carry it past the home position.  But immediately, the vector would now stretch southward, and continuing to hold the stick  back will make it change direction, to fly back north to "home".  It would just oscillate back and forth.  If you truly wanted the heli to fly south of where you are standing, you would have to get it just south of "home", and then immediately push the stick "up", commanding a movement away from home along the new vector.  The confusion would be when the helicopter is between home and your position, you'd be holding "up" but the heli would be coming towards you.  As it passes over your head, you spin around 180, and now the heli is flying away from you on a due-south trajectory as you continue to hold up.  All is right with the world.


I saw mention of a "circular" mode, maybe this is what I want?


If they need to create a new mode to do what I want, I believe it should be called "Polar", as it's like a polar coordinate system.

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