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Should we put an end to requiring a traditional Tx for Multicopters?

Started by Edgar Scott. Last reply by Edgar Scott 2 hours ago. 19 Replies

Unless I'm mistaken I feel that diydrones would rather all flights use a Tx, but are we not very close to a point where we can to put an end of the Tx for drone multirotors as the primary flying…Continue

Building Copters with Round Tubes - Stronger, Lighter, Easier to Mount Motors than Square Tubes

Started by Forrest Frantz. Last reply by Jon 4 hours ago. 205 Replies

Round tubes offer the following pros:handle twist better than square tubes.  Thus for the strength, are far lighter.are more readily available (pipes, tubes, arrows, kite frames, golf clubs and…Continue

How to load a param file into Mission Planner

Started by Bud Zirkle. Last reply by Phillip Toone 11 hours ago. 5 Replies

I'm a newbie here and not quite sure how to go about loading a param file into Mission Planner.  Don't see any options under the Configuration tab to do that.  I'm sure I'm missing something…Continue

MAVLink Tutorial for Absolute Dummies (Part –I)

Started by Shyam Balasubramanian. Last reply by Murtaza Bagwala 22 hours ago. 78 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

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Comment by avionics on December 9, 2012 at 9:45am

2012-12-09%2020-01-10.tlog

 

Hi Guys

I was in the middle of tuning for my Loiter and suddenly the quad started coming down out of control and crashed. Luckily no damage but it went out of control. this is the log i appreciate if any one can help and see what went wrong. thanks

 

2012-12-09%2020-01-10.tlog

 

Comment by avionics on December 7, 2012 at 8:16am

OK I got the Loiter going almost good. I had problem with my CH_6 knob on TX. fed the info directly from the ground station. all good for now. Thanks.

 

Comment by avionics on December 6, 2012 at 10:26pm

@Randy

Randy thank you for the response. Frankly I dont really know what to look for in the log. any idea what i should expect in the log? sorry I have never done this before.

Comment by Randy Brazeau on December 6, 2012 at 11:38am

@Avionics

Have you reviewed the logs? That would be a good starting point to see what is happening.

Randy

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.

 

 
 
 

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