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Sure is quiet around here! Whats latest word on openservo?

 
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guru



Joined: 03 Jan 2006
Posts: 128
Location: St Pete Beach, FL

PostPosted: Fri Jun 13, 2008 5:54 pm    Post subject: Sure is quiet around here! Whats latest word on openservo? Reply with quote

Hi everyone,

It seems real quiet around openservo.com lately, I hope everyone is not getting bored with it! Is OpenServo reaching it's maturity?

How is the algorithm handling the non-linear aspects of the servo now with regard to real-world external loads? I know the PID algorithm wasnt handling non-linear behavior well.

Has the hardware matured? Any new changes on the horizon? There was talk about measuring velocity directly rather than derived by changes of position.

My interest in this group is still very high, even though I haven't done much with the open servos yet. I am still finishing my cnc machine, after which I will pursue open servo applications and robotics with it.
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ginge
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Joined: 14 Jan 2006
Posts: 1031
Location: Manchester, UK

PostPosted: Mon Jun 16, 2008 8:10 am    Post subject: Reply with quote

Hi Guru,

"It seems real quiet around openservo.com lately, I hope everyone is not getting bored with it! Is OpenServo reaching it's maturity?"

I don't think there is any boredom here. Sales are still strong. I think we might be reaching something that resembles maturity, at least for the most part. I know that personally I am very busy with other things (buildng a RepRap so I can exrude a new robot) but this is not forgotten Smile

"How is the algorithm handling the non-linear aspects of the servo now"

non existant. I played with different algos from some research papers, but nothing panned out. If you have any thoughts, or know anyone with experience int his field...

"Has the hardware matured?"

Yes, The version 3 hardware is very robust (I havn't exploded one yet) has a great feature set, and is very small. There are always features we will need to add, but that goes for anything.

"Any new changes on the horizon?"

Not that I can think of. I was considering doing some small PCB layout changes to allow spare IO pins to broken out. This would be useful for the encoders.

As OpenServo is a reference platform, I have been working on scaling the design up. I suppose that could be considered new Wink

"There was talk about measuring velocity directly rather than derived by changes of position."

Yeah, Version 3 hardware does this with back EMF or (if you build you design and build your own) Hall sensors/quadrature. Back EMF, once filtered, has a very close lienear relationship to the velocity. It works so well that is is used in the PID algorithm directly.

Cheers,

Barry
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kbb



Joined: 01 Jun 2007
Posts: 180

PostPosted: Mon Jun 16, 2008 10:22 pm    Post subject: Re: Sure is quiet around here! Whats latest word on openserv Reply with quote

guru wrote:
It seems real quiet around openservo.com lately, I hope everyone is not getting bored with it!


Hi Guru,

I am constructing a biped using OpenServo V3 boards in MG995s. I don’t seem to get much time to work on it at the moment so progress has slowed. I have converted and “tested” the 12 MG995s needed, including adding heat sinks. These have been installed in a Lynxmotion “Biped Scout”. Currently I am cabling it up.

Kevin.
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guru



Joined: 03 Jan 2006
Posts: 128
Location: St Pete Beach, FL

PostPosted: Wed Jun 18, 2008 1:12 pm    Post subject: Reply with quote

Had to google RepRap...that thing is wicked! If I wasnt already deep into my cnc machine. I would be making one of those too. Almost done my machine.

Glad to hear sales are strong.

I am also thinking about scaling openservo up in the future. I wonder how it would handle the dynamics of CNC during cutting. I would use quadrature encoders of course, has this already been implemented with openservo?

How are you getting along with Solidworks now? You must be using that for the RepRap too?

Colin
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ginge
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Joined: 14 Jan 2006
Posts: 1031
Location: Manchester, UK

PostPosted: Fri Jun 20, 2008 10:11 am    Post subject: Reply with quote

Hi Colin,

You should be able to have the best of both worlds with the reprap. I don't have a stock reprap, but instead I retrofitted a new toolhead onto my CNC, you should be able to do similar.

Solidworks is still annoying me mightily. I might some help Wink

"I am also thinking about scaling openservo up in the future. I wonder how it would handle the dynamics of CNC during cutting. I would use quadrature encoders of course, has this already been implemented with openservo? "

Sort of. Check this image:-



It is currently powering my robot arm at sustained 6A load. it has 2 PWM output channels for use with stepper motors, which can be bridged for DC servo drive.
I have plans for it in my CNC, but I think we will need to improve the control algorithm some more. Those small forgivable mistakes tend to get amplified in hardware like this.

Anyways, It has 2x encoder inputs on board, and the code will be merged as soon as it works as it should Wink
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guru



Joined: 03 Jan 2006
Posts: 128
Location: St Pete Beach, FL

PostPosted: Tue Jul 01, 2008 5:35 pm    Post subject: Reply with quote

What type of CNC machine do you have? And, if you need a hand learning SolidWorks let me know. I sent you a private msg btw.

C
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ginge
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PostPosted: Wed Jul 02, 2008 11:40 am    Post subject: Reply with quote

Hi Colin,

I have a small heavily modified proxxon milling machine with a bed size of 20cm x 40cm. Not massively large, but suitable for the small robot work I do.

I just found your PM. I don't know why I didn't get the notification. Thanks Smile
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Black



Joined: 05 Jan 2015
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PostPosted: Mon Jan 05, 2015 8:54 am    Post subject: Reply with quote

I don't think there is any boredom here. Sales are still strong. I think we might be reaching something that resembles maturity, at least for the most part. I know that personally I am very busy with other things (buildng a RepRap so I can exrude a new robot) but this is not forgotten Smile
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