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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 02 April 2009, 18:22 PM Post subject: ZX Copter Update |
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Hey Guys
Just thought some of you may like to see the new larger version of my zx controlled copter.
Some of you may remember the quad from a few months back..
http://www.vimeo.com/1923952 [edit: this link may not be functional]
This is the new version, a little bigger!
http://www.vimeo.com/3974729
A short onboard clip
http://www.vimeo.com/3974721
Clip from the main development and testing area,which is a little confined as you can see!
http://www.vimeo.com/3981777
Ive lost the need for dual processors now, so this is all being done on a single zx-24n (or zx-128ne when I need more PWM out for servo control)
excuse the ugly chassis at the moment, its built for strength not appearances!
Ben
Last edited by sturgessb on 03 April 2009, 1:52 AM; edited 1 time in total |
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pjc30943
Joined: 02 Dec 2005
Posts: 220
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Posted: 03 April 2009, 1:24 AM Post subject: |
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| Can you make the links public so that a membership is not required? |
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GTBecker
Joined: 18 Jan 2006
Posts: 457
Location: Cape Coral
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Posted: 03 April 2009, 1:42 AM Post subject: ZX Copter Update |
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Last edited by GTBecker on 03 April 2009, 1:52 AM; edited 1 time in total |
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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spamiam
Joined: 13 Nov 2005
Posts: 666
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Posted: 03 April 2009, 12:32 PM Post subject: |
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Ben,
That flies really well. I always love on-barod video too! What do you find is the advantage of 8 motors vs 4? ON the "8" version, do you control each pair of motors as a single channel, or each one individually?
-Tony |
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mikep
Joined: 24 Sep 2005
Posts: 765
Location: Austin, TX
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Posted: 03 April 2009, 13:36 PM Post subject: |
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| I was impressed with the 4 rotor design. The 8 one looks even better and I guess is even more stable. How do you control everything with just a single ZBasic device? Do you use a mixture of 8 and 16-bit PWMs? I would be interested in seeing what you use each pin for or even a schematic. |
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 03 April 2009, 17:26 PM Post subject: |
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Brighter day today, here's a short movie.
http://www.vimeo.com/3989767
Mike:
I'm not using any PWM out on this one, all the motors are driven via I2C. I'm just using 1 SPI channel, 1 I2C channel, 4 ADC channels, and 1 PWM out (for a buzzer), oh and 2x UART, one for gps, one for xbee.
Tony:
They can all be controlled independently but mostly they work in pairs.
Ben |
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twesthoff
Joined: 17 Mar 2006
Posts: 191
Location: Fredericksburg, VA
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Posted: 03 April 2009, 17:33 PM Post subject: ZX Copter Update |
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It says this is a private video and won't let me see it...
ZX-24 wrote: | Quote: | Brighter day today, here's a short movie.
http://www.vimeo.com/3989767
Mike:
I'm not using any PWM out on this one, all the motors are driven via I2C. I'm just using 1 SPI channel, 1 I2C channel, 4 ADC channels, and 1 PWM out (for a buzzer), oh and 2x UART, one for gps, one for xbee.
Tony:
They can all be controlled independently but mostly they work in pairs.
Ben
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 03 April 2009, 17:37 PM Post subject: |
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| sorry, fixed! |
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mikep
Joined: 24 Sep 2005
Posts: 765
Location: Austin, TX
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Posted: 03 April 2009, 17:44 PM Post subject: |
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| sturgessb wrote: | | I'm not using any PWM out on this one, all the motors are driven via I2C. |
Presumably you are using something like the OpenServo V3 I2C Protocol and servos. That would make a total of 9 AVRs in your Octocopter. |
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 03 April 2009, 17:54 PM Post subject: |
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| No Im using standard cheapo Motor controllers from china. However I have updated their firmware to accept I2C interface rather than PWM. But you are right in thinking AVR, they use the ATMega8, so yes 9 AVRs! |
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spamiam
Joined: 13 Nov 2005
Posts: 666
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Posted: 04 April 2009, 18:55 PM Post subject: |
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| sturgessb wrote: | | No Im using standard cheapo Motor controllers from china. However I have updated their firmware to accept I2C interface rather than PWM. But you are right in thinking AVR, they use the ATMega8, so yes 9 AVRs! |
So, you are using a separate channel for each motor. I'd be interested to see how you are blending the motors located on the diagonal with the motors located on the 4 cardinal directions.
-Tony |
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 04 April 2009, 21:23 PM Post subject: |
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If I understood the question I could tell you!  |
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spamiam
Joined: 13 Nov 2005
Posts: 666
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Posted: 05 April 2009, 22:25 PM Post subject: |
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| sturgessb wrote: | | If I understood the question I could tell you! |
Well, what I meant was that it would appear that you are controlling each motor individually, rather than as a pair of motors (the pair located on the same side of the 'copter).
Since your controller uses a joystick generating up/down and left/right signals which would naturally fit 4 channels on the 'copter.
As I said earlier, it appears that you are controlling each of the 8 motors individually, 4 of them probably exactly match the joystick directions (what I would call the 4 cardinal directions). Then the other 4 are what I would call the diagonal directions.
The jist of my question was regarding you you synthesize the signals to these 4 "diagonal" motors. Are the signals synthesized as a function of the 2 adjacent motors, or it is just the same as one of the adjacent morors, or something else? The more sophisticated the functions, the more the processor time it takes to create the signal.
I am glad to see that the ZX has enough computing horsepower to do the job all by itself. I would have been very tempted to use 2 or 3 CPU's to do the job. One to handle the autonomous functions, one to handle the user-controller input, and one to take these 2 control signals and handle the job of getting the motors to do the right thing. Needless to say, there would need to be a high priority, lag-free, connection between the autonomous function CPU and the motor controller, and maybe a lower priority connection to the user-controller handler.
-Tony |
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sturgessb
Joined: 25 Apr 2008
Posts: 246
Location: Norwich, UK
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Posted: 05 April 2009, 23:01 PM Post subject: |
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Easiest way to think about it is them just working in 4 matching pairs.
The ZX n series are incredibly powerful and I found that using 2 or more processors was actually slower because of having to transfer the data across, even with the SPI link between them.
The main control loop for a quadcopter etc has to be well in excess of 300hz, this one is running at around 500hz. But the great thing about the zx devices is the multitasking allowing you to easily have slower tasks for the less frequent operations.
Ben |
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