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MAVLink Tutorial for Absolute Dummies (Part –I)

Started by Shyam Balasubramanian. Last reply by Alejandro Hincapié 3 hours ago. 74 Replies

Hi All,I was recently fiddling around the code for a while and decided to create a tutorial out of it so that others may find it useful. If I would have known this knowledge long back, I am sure I…Continue

Tags: Ardupilot, Mega, the, program, to

How to assign a receiver channel as a pass-thru Pixhawk ?

Started by Hugues. Last reply by Geert Pirens 7 hours ago. 30 Replies

Hi,I would like to configure two radio channel of my receiver to pass-through Pixhawk on its RC aux channels (that is the RC9 to RC14 aux PWM outputs).I found in mission planner the RCx_FUNCTION…Continue

Build APM 2.6 for data logger

Started by Vitalii S.. Last reply by Vitalii S. 11 hours ago. 3 Replies

Hi!I want to build small data logger for our plans. We want to use it on light gliders so every additional gram and mm has great importance. It should be really small, like 50*40*5 mm  or less ( I…Continue

Camera Pan Tilt Power

Started by Damo. Last reply by HOH yesterday. 4 Replies

With JP1 removed, is it ok to power my finwing 390 pan tilt servos from the oututs of the APM on channels 6 and 7?thanksDamoContinue

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Developer
Comment by Randy on November 29, 2012 at 1:15am

@Shyam re Quaternions,

     There's a thread by Bill Premerlani re DCM vs Quaternions.  My understanding is that they're equivalent.  II think perhaps DCM is faster but maybe not, i'm not sure.  I don't think it's as simple as one has 4 elements so it's faster than the other that has 9.

     When the copter/plane accelerates in any direction, the accelerometers sees this.  The problem is that we generally use the accelerometers to tell us which way is down.  So any acceleration of the copter/plane has the potential to throw off our attitude estimate.  Normally the accelerations are short-lived so they don't cause much problem but if they're long lived (for example you're constantly travelling in a circle) it can be a real problem.

-Randy

Comment by Shyam Balasubramanian on November 28, 2012 at 3:51pm

@Randy,

Thank you for your thoughts on implementing quaternions. I have a question, quaternions are supposed to be faster as they use 4 elements unlike DCM which uses 9, and does not suffer gimbal locks (even DCM does not, but one should know how to avoid it there though), it must result in faster computation right?

And what does "the centrifugal (centripetal) force which can throw off the accelerometers" means?

Thanks!


Developer
Comment by Randy on November 26, 2012 at 1:41am

@Shyam re "using quaternions in APM"
     We pulled out the Quaternion attitude estimation from ArduCopter after 2.6.  It didn't perform better than DCM so it was just slowing down the developers who had to maintain two parallel ahrs classes.  You can find 2.6 in the downloads area but can't make any promises about being able to support it or what incompatibilities with the mission planner may have appeared.

    If you want to try it you should add this to your APM_Config.h:

#define QUATERNION_ENABLE ENABLED

 

Now if you're talking about using the attitude estimation from the MPU6000's DMP unit (which spits out it's results in Quaternions), you can simply add this to your APM_Config.h:

# define DMP_ENABLED ENABLED

A few people on the dev team have flown it (including me) and from the limited testing we did, it's results were nearly identical to the DCM but it doesn't offer us some features that DCM does like centrifugal (centripetal?) force which can throw off the accelerometers.

 

Comment by Shyam Balasubramanian on November 25, 2012 at 8:03pm

"Quaternion implementation in APM - 1. Can somebody PLEASE give me a hint on how to use it? I am stuck."

Comment by Zachary Koh on October 31, 2012 at 8:17pm

@Brint Thanks for the suggestion! It looks pretty neat.
I am flying a custom frame so my team will have to design our own mount. How's the response of the servos for you? Are you using the ones available on the website as well?
I take it your servos are all connected to the outputs of two channels on your APM right? I was also wondering if I could use a seprate transmitter, from the one I use to fly, to control the camera rig.

Comment by Brint E. Kriebel on October 31, 2012 at 8:21am

Zachary, probably best to start a new topic for this in the forum. I just picked up one of these, though, and I am quite happy with it: http://quadframe.com/products/g01k

Comment by Zachary Koh on October 31, 2012 at 12:32am

Hey guys,

I was thinking of throwing an actively stabilizing camera rig onto my VTOL copter. Anyone has experience with camera-servo rigs? Any advice would be greatly appreciated. X)

Comment by Dean Miller on October 27, 2012 at 7:12am

Shhhh, it is the dark side of the code we are never to speak of.

 

Actually I didn't even know I posted, must be a bug in my Windows 7, fortunately Windows 8 is coming and will fix all bugs. :)

Comment by Wessie on October 27, 2012 at 2:58am

@Dean and Marooned.

I completely disagree!

I suspect there is something you are not telling us.

All this secrecy....

;-)

Comment by Marooned on October 26, 2012 at 7:35am

Dean, I generally agree.

 
 
 

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