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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Mon Mar 04, 2019 6:30 pm Post subject: Aluminium robot arm. |
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Hi,
there is no questions. Want to show my latest project, still in progress:
https://www.youtube.com/watch?v=suFuSS_XOX4
Arduinos are working with Bascom code.
Regards,
Martin |
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albertsm
Joined: 09 Apr 2004 Posts: 5913 Location: Holland
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Posted: Mon Mar 04, 2019 7:43 pm Post subject: |
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Looks like a real robot arm. I mean not a small desk one. what are the plans for the arm when it is finished? _________________ Mark |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Mon Mar 04, 2019 8:15 pm Post subject: |
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Exactly. I'm going to use it in production proces like " take, move, put".
It's significant difference between making a toy on the desk using modelling servos and using industrial stepper/servos... and in spite of
long TODO list, slowly getting closer
And thank you for nice comment:) |
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albertsm
Joined: 09 Apr 2004 Posts: 5913 Location: Holland
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Posted: Mon Mar 04, 2019 10:09 pm Post subject: |
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I will follow the project _________________ Mark |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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six1
Joined: 27 Feb 2009 Posts: 553
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Posted: Thu Jun 13, 2019 6:48 am Post subject: |
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Looks Good
But i think, you have to slow down speed, if you reach the endpoint _________________ For technical reasons, the signature is on the back of this message. |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Fri Jun 14, 2019 10:12 pm Post subject: |
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I know. This is caused by too small transmission ratio. I don't want to change setup of timer1 which is my square wave generator. Servos should work as fast as possible (to avoid jittering), transmission ratio e.g. 1:20 would fit my needs the best. Unfortunatelly have 1:6 and changing microstepping (greater) also isn't good solution for so small transmission ratio since stepper have too weak holding position capability. Currently I'm working on changing this ratio. |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Sat Dec 11, 2021 6:00 pm Post subject: |
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So finally last chapter about my first robotic arm. You can see it there https://www.youtube.com/watch?v=FdPu8XA_B-Y.
Now I can say that:
- during this project, I came to the conclusion that atmega328 is a bit too weak to parallel generate pwm signal for servo and reading servo's encoder. The workaround seems to be simply, it'd be enough to generate pwm signal on the separate MCU and talk with uC readfing encopder's signal or.. the next idea is to use xmega with quadrature encoder read registry. It is very likely direction I will follow. So far have no experience in xmega thus i count on this forum! Any help how to configure or read quadrature encoders on xmega are more than welcome
- my second project is under way: i'm going to buy scraped industrial robotic arm with removed motors. Only arm, it's about stiffness. Servos of my choice, electronic and application by me.
Regards, |
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Paulvk
Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY
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Posted: Sat Dec 11, 2021 11:57 pm Post subject: |
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The mega1284 may do it running at 20 MHz comes in a 40pin dip .
Regards Paul |
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albertsm
Joined: 09 Apr 2004 Posts: 5913 Location: Holland
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Posted: Mon Dec 13, 2021 11:22 am Post subject: |
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thanks for the video. it looks like a professional robot arm. you are right that it is about sturdy but also about repeatability. that is why it is so expensive. yours look usable. but i do not know what the ultimate goal/application is.
i played with some toy arms. they are not really usable, only to play around.
you learned a lot with your project. Xmega is a good choice for most demanding projects. but of course you can also take 2 tiny, megaX or DB chips. _________________ Mark |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Mon Dec 13, 2021 1:34 pm Post subject: |
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initially indeed it was meant as a toy but with time I decided to develop fully scaled application that I could use in my next project (I'm going to buy scrapped robotic arm, probably old Fanuc arm). I decided to use hybrid steppers Nema34, torque =9 Nm*planetary gearbox1:10 => 90Nm, so need to generate very fast pwm signal. And now comes the question which uC to use to control position of the stepper and parallel generate pwm. Paulvk suggested atmega1284. I checked specs and it seems to be fine but on the other hand there are xmegas. Especially with encoder's register which suits my needs. The problem is however that I know less than little about xmegas Currently in Poland i can buy this: https://kamami.pl/minimoduly-avr/557590-xmega-exploree5-z-atxmega32e5.html.
Between Christams and New year i'm going to play a little with 1284. Maybe in January I'll come to some conclussion regarding this uC.
However any suggestions about xmega and setting the register for reading the encoder are welcome
Regards,
Martin |
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JC
Joined: 15 Dec 2007 Posts: 584 Location: Cleveland, OH
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Posted: Mon Dec 13, 2021 2:46 pm Post subject: |
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What a great project!
All of the Xmegas are the same... Except the X32E series...
There are a few differences within it compared to the large pin Xmegas.
One point to remember with the X32E5 is that for many of the interrupts one has to clear the interrupt flag yourself, by your software, within the ISR code.
The ISR flag is not automatically cleared just by executing the ISR, (which it is in the older Megas and Tinies).
However, Bascom makes it easy to use the Xmegas and the new AVR DB series chips.
At times the extra speed of the Xmega, 32 MHz, is helpful.
I don't know if you are doing a lot of floating point calculations for the motions to move the arm, or if those are being done by the PC.
What a great project!
Thanks for posting the videos.
JC |
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krolikbest
Joined: 02 Jan 2017 Posts: 112
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Posted: Mon Dec 13, 2021 3:14 pm Post subject: |
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Thank you
acording to floating point operations - avoid them like plague. No, there is only integer operation in atmegas. The main calculations are made by PC, RPi actually. |
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Paulvk
Joined: 28 Jul 2006 Posts: 1257 Location: SYDNEY
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Posted: Mon Dec 13, 2021 9:40 pm Post subject: |
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I found the 1284 a very useable chip but the main reason I suggested it is because its 5 volt
20mhz and should require minimal circuit changes you may even be able to overclock it to 25mhz
Besides the electronics being great very nice machining work you have done.
Regards Paul |
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hgrueneis
Joined: 04 Apr 2009 Posts: 902 Location: A-4786 Brunnenthal
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Posted: Mon Dec 13, 2021 11:09 pm Post subject: |
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Paul,
I use a Xmega for a main Controller and have seven Atmega168 connected to it, that do the sampling of sensors and so on and outputs.
Have some of these run at 24MHz without problems. At VCC 5.0 volt and IF to the 3V Xmega.. If you supply 5.5 it can be clocked reliably higher.
For servo speed control I use a distance to endpoint percentage algorithm for speed up and slow down. Works well and does not need a license from Fuzzy Logic. Also used 1284s without problems (a great chip with lots of memory and ports).
Regards
Hubert. |
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