Servo motor hardware

More
19 Dec 2010 22:20 - 19 Dec 2010 22:46 #6171 by mort
Servo motor hardware was created by mort
I have a few 600 watt brushless 3 phase 100 VDC motors lying around that use hall sensors for commutation. Is it possible to just buy just servo encoders separate and in effect turn these into servo motors? My electronics background is limited and I cant seem to find the distinguishing point between a servo and plain motor other than encoder/resolver feedback. Ive looked through several on used hardware websites and there are numerous used Heidenhain encoders available. Im looking into mounting these on the X and Y axis of a BP mill clone. If it is possible, why type of encoder feedback signal is best? TTL, Vss, etc. The mill already has linear 1 Vss encoders for a DRO and I would like to make use of those if possible for position feed back.
Last edit: 19 Dec 2010 22:46 by mort. Reason: typo..

Please Log in or Create an account to join the conversation.

More
19 Dec 2010 23:48 #6177 by marzetti
Replied by marzetti on topic Servo motor hardware
I would check with Jon Elson at Pico Systems ( pico-systems.com/oscrc4/catalog/index.ph...91eca4c24bffafc9b0c2 ). He offers a PWM brushless servo amp that may work for you.

Best regards,
Greg Bernard

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 13:59 #6181 by andypugh
Replied by andypugh on topic Servo motor hardware
mort wrote:

I have a few 600 watt brushless 3 phase 100 VDC motors lying around that use hall sensors for commutation. Is it possible to just buy just servo encoders separate and in effect turn these into servo motors?


Yes. As well as the Pico drive already suggested the Mesa 8i20 might be a good fit. Support is still experimental (the drive parameter setup is not settled yet). There is a HAL component that will start the motor using the Hall sensors, then switch to sinusoidal commutation using the encoder once it gets an angle fix.

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 17:36 #6183 by mort
Replied by mort on topic Servo motor hardware
I plan on using TTL encoders for the servo and I guess ill have to get interpolation boxes for the position encoders since they output sinusoidal signals. Is it possible to mix signal types??

Also, is it possible to configure drives such as Siemens, Parker, or Kollmorgen to work with Pico or Mesa controllers? Im wandering why I dont see EMC using many other brands of hardware. Seems like its mainly only Pico or Mesa. Is it that hard or impossible to configure other brands of hardware to work with EMC?

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 18:07 #6185 by PCW
Replied by PCW on topic Servo motor hardware
Note that EMC supports many kinds of _drives_ including the ones listed, as long as they have
analog +-10V, Step+Dir, or PWM inputs. Suppliers of interfaces for servo drives include Vital systems, Mesa, and Pico Systems. Theres some preliminary support for EtherCat drives as well. Other interface hardware can be supported by EMC but this requires

1. The hardware be capable of real time control (this rules out most USB devices or "smart" buffered devices)

2. Hardware documentation be available

3. An interest by a developer in supporting the hardware

Note that many drives are designed to work only with matched motors, I think this is why the Mesa and Pico system drives were suggested (they can are made to work with most motors and I think
you suggested that you had bare motors and no drives)

BTW TTL level(single ended) encoders are probably not a good idea for 600 W motors. Differential encoders will have much better noise rejection characteristics

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 18:39 #6186 by andypugh
Replied by andypugh on topic Servo motor hardware
mort wrote:

I guess ill have to get interpolation boxes for the position encoders since they output sinusoidal signals. Is it possible to mix signal types??

To an extent you can do anything you can imagine with EMC. However you need to consider how you are going to get the DRO feedback into the EMC2 PC, as the available realtime interfaces are fairly exclusively digital. If you can find a way to convert the sinusoidal voltages to something which looks like an encoder, then it should be straightforward.
However, whilst it is possible to combine ballscrew feedback with DRO scales, it might be more trouble than it is worth.

Also, is it possible to configure drives such as Siemens, Parker, or Kollmorgen to work with Pico or Mesa controllers? Im wandering why I dont see EMC using many other brands of hardware. Seems like its mainly only Pico or Mesa. Is it that hard or impossible to configure other brands of hardware to work with EMC?

The other drives you describe tend to be "intelligent" drives with internal PID controllers and lots of features that EMC2 does not need. EMC2 is most effective with dumb drives, and the PID calcs performed in the PC (with the considerable advantage that you can monitor them with Halscope). With the other drives you mention you will be paying for a lot of features that you won't be using, and might need special cables/software to disable. The only reason to use those drives would be if you got them cheap. (from eBay for example)

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 18:40 #6187 by mort
Replied by mort on topic Servo motor hardware
Now I thought a differential encoder was a TTL encoder? This is such a confusing aspect for me. Is there anywhere I can read on encoder output signals, compatibility, pros/cons etc. Ive skimmed through the emc manuals and havent found anything that discusses this... though I may have simply overlooked it. The encoders im looking at are Heidenhain ROD 426 and maybe some of the ExN series. These seem to be everywhere. I plan on using them for larger motors in the future. I just wanted to try out emc and the pico or mesa hardware on these smaller motors before I start spending bigger bucks on larger ones.

"BTW TTL level(single ended) encoders are probably not a good idea for 600 W motors. Differential encoders will have much better noise rejection characteristics "

Are TTL better for higher power motors?

Thanks for the help!!!

Please Log in or Create an account to join the conversation.

More
20 Dec 2010 18:51 #6190 by andypugh
Replied by andypugh on topic Servo motor hardware
mort wrote:

"BTW TTL level(single ended) encoders are probably not a good idea for 600 W motors.
Are TTL better for higher power motors?


In this context, 600W are high power motors. Low power motors where TTL signal level encoders would be suitable would be in the 24V / 100W range.

TTL encoders share a 0V line between all three channels (and probably also the power supply) and output a 5V signal. Noise on the 0V line (or the 5V) line due to interference can cause problems.

Differential encoders have each signal as a positive and negative pair. Your signal is the difference between the two lines, not their absolute value, and so the level of interference rejection is a lot higher.

Having said that, some people report good results with the US Digital encoders, and they are almost cheap enough to try experimenting with.
usdigital.com/products/encoders/incremental/rotary/kit/e4p/

Please Log in or Create an account to join the conversation.

Moderators: cncbasher
Time to create page: 0.096 seconds
Powered by Kunena Forum