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Sub 250 Gram Pixracer Build - Parts

Started by Edgar Scott. Last reply by Forrest Frantz 17 hours ago. 28 Replies

Since my Sub 250 gram pixracer is complete I thought I would share a parts list and some build pics.The FC is a small 36x36 Pixhawk based, its capable of full autonomous waypoint flights, ACRO, has…Continue

Problem with Hexacopter using APM 2.8

Started by Darius. Last reply by Doug Adduci yesterday. 30 Replies

Hello, I recently purchased a Tarot 690s hexacopter , it was partially assembled (e.i the ESCs and UBEC were already soldered to the PDB). The Flight controller is an Arducopter APM 2.8 and the TX/RX…Continue

Go to waypoint after Loiter_Unlimited command

Started by Murdanny Mukhtar. Last reply by Murdanny Mukhtar yesterday. 2 Replies

Hi all,I currently have the following commands on my mission.1) Takeoff2) Loiter_Unlimited3) WP According to the article on the MAV_CMD:The mission will not proceed past this command while in AUTO…Continue

sonar height control

Started by velonica boo on Wednesday. 0 Replies

hi , im using pixhawk and mission planner 1.3.37. Can anyone share with me how to control the altitude using sonar ? when i switch to alt hold , my copter will keep flying up , may i know why ? Continue

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Comment by Andrew McKinstry on December 17, 2012 at 10:10am

Hello.. Shiny new hexa with all the toys about to leave bench (I hope).. however prop clearance issue! Or am I missing something.. 880 motors 11x4.7 props

thanks

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!

 
 
 

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