Servo Systems(drives, encoders, etc)

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Solidus
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Servo Systems(drives, encoders, etc)

Post by Solidus » Sun May 15, 2005 9:49 pm

I have very many ideas on forms of locomotion in robotics but for the life of me I can't figure out what to use for "motion drives" so to speak. Many people speak of the use of servo and stepper motors. My questions are:
(I need these motors to be fairly powerful or at least not hobby servos)<p>1: Which is best?
2: Does one need to use servo drives in robotics or is there another way?
3: Examples on programming of such devices?<p>Please help! Once I overcome this obstacle everything else will fall into place!<p>Any information is appreciated

ian
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Re: Servo Systems(drives, encoders, etc)

Post by ian » Mon May 16, 2005 1:26 pm

Well Solidus, you've created an interesting situation which is going to create a philosophical rift. I know you didn't mean to do that but you have, and now it will play itself out in real time.<p>You see Solidus, there are a number of groups here.........
There is a group who just love to help, no matter how difficult or complex the situation is, or how uneducated the asker is. As long as you try to understand they will help you.<p>There are others who will assess the futility of helping you. If you have to ask what a stepper motor is, they will wonder how explaining it will help since you're so far from any capable measure of using one that explaining its operation is futile. <p>And there is a third group who just like to demonstrate how intelligent they are, with no regard of whether you understand them or not. This is just a forum for them to swagger, and you are an unwitting participant, asking questions which will set them off. <p>I, sir, am of the second group. Good luck!<p> Ian

Engineer1138
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Re: Servo Systems(drives, encoders, etc)

Post by Engineer1138 » Mon May 16, 2005 2:06 pm

If hobby servos don't have the torque, the next cheapest/easily available source would be small power screwdrivers. You can usually get them for about $20 each at hardware stores and they have pretty high torque, but low speed. Easy to control on/off with relays or FETs.<p>If you do need high speed/high torque servos, go check out something like www.geckodrive.com but be prepared to open your wallet wide :) <p>OK, that only took 3 edits to get it right!<p>[ May 16, 2005: Message edited by: Engineer1138 ]<p>[ May 16, 2005: Message edited by: Engineer1138 ]<p>[ May 16, 2005: Message edited by: Engineer1138 ]</p>

Solidus
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Re: Servo Systems(drives, encoders, etc)

Post by Solidus » Mon May 16, 2005 4:12 pm

I know what a stepper and servo motor is and the differences. What I am asking is how to integrate them into projects b/c I see motor drives out there and other devices but I don't understand how to integrate them into robotics. Keep in mind I am speaking also about devices suplemental to the motors(drives,encoders,etc not just the motors <p>So let's think. While you were telling me about the futility of answering my questions you could've easily given me links, a starting point, and/or other information so that I could've learned something and at this moment I could be doing more in-depth research. Thanks so much!

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sofaspud
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Re: Servo Systems(drives, encoders, etc)

Post by sofaspud » Mon May 16, 2005 4:38 pm

Solidus, I don't think ian was trying to take a swipe at you personally. He was just describing the reality of the situation.
I lean towards the first group, simply because I believe that was and is the intent of Nuts & Volts publishers in creating and hosting this forum. But this is the Internet and some patience must be had for pompous misanthropic geezers, cynical techies, and every other sort.
I don't have any juicy information to pass on to you. I'm not sure what it is you want to learn. What type of motor, etc. depends greatly on the specific application. You've no doubt seen the Robotics section of this forum, and I'm certain your request is better suited there. I also suggest doing a Google search for robotics topics, and checking out the websites for motor and encoder manufacturers. They're bound to have technical, application, and programming data. You'll probably find white papers on theory of operation, too. Your local library probably has electronics and mechanical books that would help. It should be enough for a start.<p>[ May 16, 2005: Message edited by: sofaspud ]</p>

Will
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Re: Servo Systems(drives, encoders, etc)

Post by Will » Mon May 16, 2005 4:54 pm

Solidus,
Ian forgot to tell you that there is a fourth type i.e one which is relatively uneducated in technical terms but likes to keep using them so that readers may think they are a type 3. What they lack in substantive knowledge, they try supplement with insults. Ian is a founder (If not the only) member of this group of which any member is, by definition, also a member of group three.
BB

Solidus
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Re: Servo Systems(drives, encoders, etc)

Post by Solidus » Mon May 16, 2005 6:56 pm

Well here, I suppose I was a little ambiguous so let me elaborate. I have many ideas involving bipedal motion and constructing and manipulating inverted legs. Well for certain joints I would like to use a motor of some sort but I'm not sure whether a stepper is ideal for this or some sort of powerful servo. Furthermore my other concern is how would these devices be linked with some sort of computer or processor. I have thoughts of using a typical pc motherboard and some sort or pci driver to run it but that seems impractical for robotics. I have pseudo code written and actual useful code written for what I want it to do but im not sure how to put everything in one autonomous package. Any thoughts,opinions, or tips are appreciated.

Solidus
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Re: Servo Systems(drives, encoders, etc)

Post by Solidus » Mon May 16, 2005 7:00 pm

One other thing... I've read up on different microcontrollers and such but I think, for this kind of project, something more advanced is necessary.

ian
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Re: Servo Systems(drives, encoders, etc)

Post by ian » Mon May 16, 2005 7:18 pm

Listen Will, maybe I was a little hard on you in the other thread but it was a hot topic which you jumped into without reading the posts correctly, without doing any research, and started argueing wrong information.
I suspect by now you've done enough research to know how wrong Chris is and how off his numbers are. I did a lot of work to come up with correct numbers which I can defend, so don't put me in the know nothing camp.
I'll forget it if you'll forget it, water under the bridge and all that other stuff.

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philba
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Re: Servo Systems(drives, encoders, etc)

Post by philba » Mon May 16, 2005 8:36 pm

there are two types of people: those that categorize people and those that don't.
------------------------------------------<p>Steppers are tricky to get good speeds out of but are very easy to precisely position. Steppers require more sophisticated drive electronics (though I believe overall costs will be close for a given level of power).<p>Servos are very easy to use and usually don't require a lot of additional electronics. Cheap if you are building a small robot. Positioning with servos is not so easy unless you add quadrature encoders (additional expense).<p>I'd check out the seattle robotics society (yahoo group) as they are currently discussing bipedal robotic motion.<p>And finally, ignore the bitching and complaining of others. focus on your project - sounds like a lot of fun.

Gorgon
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Re: Servo Systems(drives, encoders, etc)

Post by Gorgon » Wed May 25, 2005 1:20 pm

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Solidus:
One other thing... I've read up on different microcontrollers and such but I think, for this kind of project, something more advanced is necessary.<hr></blockquote><p>Hi Solidus,
I think this microcontroller will be more in your street regarding complexity. <p> http://www.semiconductors.philips.com/m ... ons/32bit/ <p> http://www.hitex.co.uk/arm/lpc2000book/index.html <p>There are several third party suppliers of very good evaluation boards and software, at a decent pricelevel. The ARM processor is lowcost and of high capacity, a very good choice for a bit more 'juice' in processing power. ;) <p>TOK
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

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