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Sonar for walls

Started by Newtoon. Last reply by Javier Poole Derqui 5 hours ago. 5 Replies

Hi everybody !For my next project, I would like to build a quad capable of not a hitting a wall while climbing (to follow a building for instance) and not the ground, like what this guy did …Continue

Tags: sonar

PixHawk Out of Box Problems

Started by Bruce Jones. Last reply by Patrick 10 hours ago. 39 Replies

Yesterday I received the PixHawk I ordered on January 2nd.  Four week delivery time is pretty good for a new FC from 3DR!But I've had all kinds of problems trying to use it. First I tried using the…Continue

ArduCopter Pixhawk HITL

Started by Tweeter. Last reply by Jani Hirvinen on Thursday. 1 Reply

Hey All,Is there currently support for an ArduCopter Hardware in the loop on the Pixhawk?Thanks!Continue

APM 2.6, AC 3.1.5 - Loiter mode issue - found loose GPS battery and terminals inside 3DR gps casing!

Started by PF. Last reply by PF on Tuesday. 10 Replies

Hello,My HL octo is flying great with APM2.6 (w/ 3DRuBlox w compass) and AC3.1.5, but I have challenges in loiter. I can take off and enable loiter. Then the octo will stand perfectly steady, for…Continue

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Comment by avionics on December 6, 2012 at 11:04am
I have a H.A.L quad by hobby king with 1200kv motors and freshly assembled. It flies beautiful in stablise and alt Hold and when i try to loiter it doesnt hold its position. The GPS both LEDs are locked and steady before i start. It drifts and loses altitute very slowly. Tried playing with PIDs but no luck. I ran out of ideas appreciate if anyone can throw some light. Does the WP loiter config PIDs have any effect whilst on loiter or it is only for when on Auto mode? Thanks for the help in advance.
Comment by Chris Gough on November 29, 2012 at 1:36am

@Shayam, if you want to experiment with quaternions, DCM, euler angles, etc. you might want to check out the various pluggable AHRS subsystems in paparazzi.

http://paparazzi.enac.fr/wiki/Subsystem/ahrs

Comment by Shyam Balasubramanian on November 29, 2012 at 1:24am

@Randy, Thanks for that nice explanation on accelerometer with quads! Now, my understanding gets better.

I would want to try out Quaternions once myself, it seems different people are having different opinion. My friend, who works purely on Quad uses quaternion. He mentioned to be that it was 'much' faster than DCM. But, since truth is one but scenarios differ, I will ask him if he can lend me some benchmarking ;)


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)

 
 
 

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