Third party ethercat motion controllers

[maherhome]

We are looking for recommendations for 3rd party EtherCAT motion controllers to integrate with a cRIO system.  I am aware of this article.  We will be driving 5 rotary brushless motors (moving them a couple of "steps" movements at 400 Hz).  They have high resolution encoders (something like 1.2m positions per revolution).

We have spoken to Beckhoff but they don't support the high resolution of our encoders.

Any recommendations would be greatly appreciated.

Steve

[Highland_Controls]

Are you looking for an EtherCAT master motion controller or EtherCAT slave drives? What do you mean by "steps movements at 400Hz"?  What encoders are you using? 

[maherhome]

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Highland_Controls wrote:

Are you looking for an EtherCAT master motion controller or EtherCAT slave drives?

I am under the impression the cRIO wants to be master - therefore we are looking for slave drives

What do you mean by "steps movements at 400Hz"? 

This was a feeble attempt to convey our usage pattern.  The controllers will provide small mirror adjustments (i.e., small motor movements) at a rate of 400 Hz.  This may not matter at all for this discussion.

What encoders are you using? 

I think the answer to this is that we are buying five of these and they have encoders built-in (I think 1.4M steps pre rotation).

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[Highland_Controls]

I still don't know what encoder you are using.  There are a bunch of options listed.  Please provide exact type of encoder.

I think you are going to have issues moving something like that at 400Hz.  Are your mirrors big?  That is typically an application for piezo motors or galvanometers.

[maherhome]

I don't know the exact encoder.  But don't worry about that or the mirrors we're moving, etc. - we have plenty of experienced folks here [NASA Goddard] spec'ing these types of things.  

Pop the stack a bit ...  I'm only interested in names of other companies who have motion controllers that folks here have successfully integrated as EtherCAT slaves with a cRIO system.

Thanks,

Steve

[Highland_Controls]

Hi Steve-

I'll ask for forgiveness in advance for getting on my soapbox, and somewhat hijacking your thread.  I ask the questions I ask because they are important.  I come across many customers that ask for a motion controller, drive, motor, etc, and they say that want to move something from X to Y.  They then don't understand why I ask all the questions that follow.  There are a lot of details of how the system operates that need to be determined before components can be selected.  That comes from experience.  Experience of upset customers that have a system that doesn't do what they wanted it to do, because they never gave the details of what they wanted it to do.

I ask about the encoder, because certain drives can only deal with certain types of encoders.  Finding an EtherCAT drive is one step, but it doesn't do you any good if it can't read your encoder.  You may also want to not use the term "motion controller" when referring to the slave drive.  The cRIO will be the motion controller, and the slave is just a positioning drive.  I also ask about loads, speeds, etc., because there are always physical limitations to what a servo system can do.  The rotary table you selected has a fair amount of inertia, and getting it to respond to 400Hz commands will be difficult.  Again, this is just from experience.

I am also sure there are many smart people at Goddard, but that doesn't mean they know about such a specialized application.  I have worked with 4 different groups at NASA Lewis, and they call me when there is a motion control issue.  They know their applications inside and out, and what they want it to do, but then they need someone else to actually implement it.

And finally, to answer you question.  I do apologize for not doing that previously.  I have worked with cRIO;s, and with many servo systems, but I have never used cRIO and EtherCAT.  Yaskawa Sigma-5 is an excellent drive(standard servo motor it uses has over one million counts per rev), and is available with EtherCAT.  I know that some time ago, they were developing it to work with 3rd party motors.  I am not sure where that is.  Other drives that I have worked with that have EtherCAT are the ABB ACSM1, and the Gefran ADV200.

Regards,

Brian

[maherhome]

Thanks Brian. We are actually reevaluating a bit and are realizing we could probably also get by with a rs232 or 485/422 interface, which would probably make things easier from the crio side. It's great folks like you are here to help. I will probably have followup questions in the future.

Steve