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Compumotor Plus stepper drive
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eric
Ron Wickersham wrote:
yes, when equipped with a hi-resolution position sensor (such as aI have at least one synchro resolver in the junk drawer. Are they really high resolution, or just as good as analog can get? I guess you could have more than one sine wave per rev and get more resolution. I pretty much have written the thing off myself, seeing how encoders are pretty cheap. eric |
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Carey L. Culpepper
I have spent the whole day trying to get a Compumotor Plus drive to run
a motor with step-direction inputs. I downloaded the manual and have gone through it several times. The drive has a computer on-board that sets everything. Everything is set through serial port commands including current rating and microstepping resolution. The problem is that the units are designed to be used with motors with built in resolvers.The manual specifies that it will not accept encoder input.If the motor gets a pulse, it is expected to turn a step. If it doesn't it keeps trying or gives an error message. It operates just like a servo motor and is tuned accordingly with a series of switches or through the RS232. I have gone through the manual several times trying to find a command that would let me run it without the resolver. All I found were commands to set the amount of allowable error. So, I shut it down and got my screwdriver and had a "look under the hood". Three PCB,s one with the computor circuitry,one small board with the display and tuning switches, and the power supply/driver board. I found three jumpers together on the computer PCB. My question is this: Is it possible to run these drives without the resolver input? Anyone familiar with these units. They are very sophisticated. I am impressed. If only I had motors with resolvers. These are made to be run closed loop. |
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Steve Carlisle
Are these pulse driven servo amplifiers(drives) ?
Steve ---------- From: Carey L. Culpepper <mr.c@...> To: CAD_CAM_EDM_DRO@... Subject: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive Date: Saturday, July 01, 2000 7:20 PM I have spent the whole day trying to get a Compumotor Plus drive to run a motor with step-direction inputs. I downloaded the manual and have gone through it several times. The drive has a computer on-board that sets everything. Everything is set through serial port commands including current rating and microstepping resolution. The problem is that the units are designed to be used with motors with built in resolvers.The manual specifies that it will not accept encoder input.If the motor gets a pulse, it is expected to turn a step. If it doesn't it keeps trying or gives an error message. It operates just like a servo motor and is tuned accordingly with a series of switches or through the RS232. I have gone through the manual several times trying to find a command that would let me run it without the resolver. All I found were commands to set the amount of allowable error. So, I shut it down and got my screwdriver and had a "look under the hood". Three PCB,s one with the computor circuitry,one small board with the display and tuning switches, and the power supply/driver board. I found three jumpers together on the computer PCB. My question is this: Is it possible to run these drives without the resolver input? Anyone familiar with these units. They are very sophisticated. I am impressed. If only I had motors with resolvers. These are made to be run closed loop. ------------------------------------------------------------------------ Click for more information on how eGroups members save with beMANY! ------------------------------------------------------------------------ Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems, for CAD, CAM, EDM, and DRO. Addresses: Post message: CAD_CAM_EDM_DRO@... Subscribe: CAD_CAM_EDM_DRO-subscribe@... Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@... List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@... Moderator: jmelson@... [Moderator] URL to this page: FAQ: bill, List Manager |
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Darrell
Stepper motors do not have resolvers. Some servo motors have resolvers. That
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driver is for running servos with step and direction signals. Darrell ----- Original Message -----
From: Carey L. Culpepper <mr.c@...> To: <CAD_CAM_EDM_DRO@...> Sent: Saturday, July 01, 2000 7:20 PM Subject: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive I have spent the whole day trying to get a Compumotor Plus drive to rundiscussion of shop built systems, for CAD, CAM, EDM, and DRO.
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Carey L. Culpepper
Darrell: Read my lips! I said that I spent a day pouring through the
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manual that is pretty clear that these are stepper drives and are ,in fact, designed to drive Compumotor steppers with built in resolvers.Better yet, why don,t you pop into the their web-site and see for yourself. www.compumotor.com/literature.htm then click on user guides and then Compumotor Plus user guide.Be advised that they do call it a " servo system" but read on. A servo system using resolver equipped stepper motors.A very impressive setup,if you have the right motors. Thinking about the possibility of putting a stepper motor in place of my encoder and using it as a resolver. If only I knew how to wire it. Let me know what you think. Carey Darrell wrote: Stepper motors do not have resolvers. Some servo motors have |
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hi Carey,
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unfortunately while a resolver (a two-phase field syncro) can be connected as a motor and will produce a little power, a two-phase stepper cannot be connected to function as a resolver. the resolver has a reference phase (a single-phase winding on the armature) while the stepper motor uses a permanent magnet armature (at least in the type of stepper motors discussed here for machine drives). there is a lot of work (and some patents issued) on detecting the position of a stepper armature without additional encoders or windings, but there is no way to connect a stepper to a resolver input, since there is no output of the stepper when stopped. the resolver, however, works when stopped due to the ac excitation of the armature. yes, when equipped with a hi-resolution position sensor (such as a resolver, or encoder) there is no distinction between a stepper motor and a brushless dc servo motor. -ron On Sun, 2 Jul 2000, Carey L. Culpepper wrote:
Darrell: Read my lips! I said that I spent a day pouring through the |
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Steve Carlisle
Compumotor offers encoders(incremental) and absolute
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encoders(resolvers) on their stepping motor packages. Resolvers are quite common in the higher end motion control applications. Steve ---------- From: Darrell <dgehlsen@...> To: CAD_CAM_EDM_DRO@... Subject: Re: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive Date: Sunday, July 02, 2000 12:08 AM Stepper motors do not have resolvers. Some servo motors have resolvers. That driver is for running servos with step and direction signals. Darrell ----- Original Message -----
From: Carey L. Culpepper <mr.c@...> To: <CAD_CAM_EDM_DRO@...> Sent: Saturday, July 01, 2000 7:20 PM Subject: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive I have spent the whole day trying to get a Compumotor Plus drive to rundiscussion of shop built systems, for CAD, CAM, EDM, and DRO.
------------------------------------------------------------------------ Lonely? Get Firetalk! Free, unlimited calls anywhere in the world. Free voice chat on hundreds of topics. ------------------------------------------------------------------------ Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems, for CAD, CAM, EDM, and DRO. Addresses: Post message: CAD_CAM_EDM_DRO@... Subscribe: CAD_CAM_EDM_DRO-subscribe@... Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@... List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@... Moderator: jmelson@... [Moderator] URL to this page: FAQ: bill, List Manager |
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Carey L. Culpepper
Ron: Thanks for your reply. Here is what the user manual has to say
about their resolver: A brushless resolver made of the same rotor and stator components used in the motor was developed. This resolver is magnetically similar to the motor itself, and is manufactured as an integral part of the motor. The result is a sensor with the same number of poles as the motor( which makes control straightforward) that is always properly aligned with the motor and can be operated in high noise, high temperature environments." This is what led me to believe that a motor might be wired to do the same thing. |
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Steve Carlisle
Very high resolutions can be obtained. Over 65,000 counts
on some systems. They are generally used on high end systems, are are complex and costly. Steve ---------- From: eric <eek105@...> To: CAD_CAM_EDM_DRO@... Subject: Re: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive Date: Tuesday, May 20, 1997 3:29 PM Ron Wickersham wrote: yes, when equipped with a hi-resolution position sensor (such as aI have at least one synchro resolver in the junk drawer. Are they really high resolution, or just as good as analog can get? I guess you could have more than one sine wave per rev and get more resolution. I pretty much have written the thing off myself, seeing how encoders are pretty cheap. eric ------------------------------------------------------------------------ Free Conference Calling with Firetalk! Host your next egroup meeting live on Firetalk. Click here! ------------------------------------------------------------------------ Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems, for CAD, CAM, EDM, and DRO. Addresses: Post message: CAD_CAM_EDM_DRO@... Subscribe: CAD_CAM_EDM_DRO-subscribe@... Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@... List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@... Moderator: jmelson@... [Moderator] URL to this page: FAQ: bill, List Manager |
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Steve Carlisle
This sounds like it may be a propriotry type resolver
made for that system. Contact Compumotor and find out if a standard resolver is compatible. I think you are going to find that this system is way be-yond your needs, and patience. Steve ---------- From: Carey L. Culpepper <mr.c@...> To: CAD_CAM_EDM_DRO@... Subject: Re: [CAD_CAM_EDM_DRO] Compumotor Plus stepper drive Date: Monday, July 03, 2000 3:09 PM Ron: Thanks for your reply. Here is what the user manual has to say about their resolver: A brushless resolver made of the same rotor and stator components used in the motor was developed. This resolver is magnetically similar to the motor itself, and is manufactured as an integral part of the motor. The result is a sensor with the same number of poles as the motor( which makes control straightforward) that is always properly aligned with the motor and can be operated in high noise, high temperature environments." This is what led me to believe that a motor might be wired to do the same thing. ------------------------------------------------------------------------ Free Worldwide Calling with Firetalk! Click Here: ------------------------------------------------------------------------ Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the discussion of shop built systems, for CAD, CAM, EDM, and DRO. Addresses: Post message: CAD_CAM_EDM_DRO@... Subscribe: CAD_CAM_EDM_DRO-subscribe@... Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@... List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@... Moderator: jmelson@... [Moderator] URL to this page: FAQ: bill, List Manager |
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Carey L. Culpepper
Steve: Correct on that one. I sent off a money order today for 3 new
Warner Elec. microstepping drives. Another ebay aquisition. I just want to get my conversion up and running. Fortunately I have very little money invested in the Compumotor Plus drive. I will probably still mess around with it to see if I can get it to respond. I would hate to venture a guess what those drives cost new. It would scare me! |
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Jon Elson
"Carey L. Culpepper" wrote:
Ron: Thanks for your reply. Here is what the user manual has to sayThis is not really a resolver, but a permanent magnet encoder. Yes, if you turn a stepper motor by hand, you will get voltages out. The only problem with the stepper-"resolver" is that, since it is excited only by the moving magnets causing flux lines to pass through the windings, very slow motion will not register. So, if you use a high microstepping resolution, and program extremely slow motion, whole steps could be lost. If you use fairly low microstepping, I think it should work fine. There have been some stepper drivers that detected stalls and missed steps by detecting either the current fluctuations or voltage excursions when the motor was moving, using the motor's own windings and magnetics. Jon |
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hi Cary,
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some resolvers do use brushes (they work against slip rings, not commutators) to excite the rotor field. however to eliminate the brushes entirely you often see a rotary transformer to couple the excitation to the armature. this makes a brushless resolver a very reliable component indeed. they can be used immersed in oil, dirt, and as noted in your manual operate happily at high temperatures. they are used where no other will operate (LED output goes way down at elevated temperatures, for instance). resolver systems don't compete favorably compared with optical encoders when the encoders are up to the task. a large part of the resolver system is the resolver-to-digital encoder which consists of quadrature analog channels and the reference phase generator which must have low waveform distortion for high accuracy. but for large machines such as a lathe for ship drive shafts where it is impractical to re-zero an axis and an error could destroy a very expensive part after weeks of machining, a nest of resolvers, geared so each is within the resolution of the one above, can give absolute position after a power failure. the cost of the resolver system is a small part of such a machine. i don't know the unit you have, but at Lawrence Berkeley Labs i saw an application of a Compumotor drive (incorporated in a goniometric photometer) which with no reduction gears, i.e. direct drive, with the motor axis horizontal, moved heavy components at the end of a 1.5 meter arm with just the bearings in the drive, brought cabling thru a 50 mm central tube in the axis of the drive, while achieving accuracy of less than a few arc seconds at speeds that could be slower than the rotational speed of the earth. i didn't ask the price, but the government was able to afford it. resolvers still have applications :-) -ron On Mon, 3 Jul 2000, Carey L. Culpepper wrote:
Ron: Thanks for your reply. Here is what the user manual has to say |
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