How many axes can I create on cRIO 9068 and 9042 using SoftMotion Drive Interface (SDI)?

[Flegon]

How many axes can I create using softmotion drive interface with Ethercat (CoE)? What is the maximum frequency can I set on the control loop for the movements? Is there a formula to estimate what is the maximum frequency depending on the number of axes on the chain?

[Flegon]

I am planning to control 20 axes from Delta Electronics, using softmotion SDI. I am not finding to much information about this kind of control.

[Karl-G]

Thanks for your question. SoftMotion Drive Interface axis count on a particular target is dependent on several things: the CPU of the RT target, the Scan Engine period (which controls the EtherCAT update rate and the rate at which position setpoints are sent to the drive), and other load on the target. The compatibility guide linked below shows the supported Scan Engine periods for each SDI Plug-in, and the Delta ASDA-A2-E drive supports up to 1, 2, 4, and 5ms periods.

http://www.ni.com/white-paper/53657/en/

Because of the high variability in the 'other loads' on the target, we have not published hard requirements. However, I can give you some estimates based on internal testing. The cRIO-9068 is a fairly mature product, and it's dual-core ARM CPU will only support ~10 SDI axes at a 5ms period. The cRIO-9042 is one of our latest targets, with a quad-core Intel Atom CPU. It should support 20 SDI axes at 4ms without issue, and 2ms may be possible depending on the specific applications' requirements.

[Flegon]

Thanks for your reply.

Delta company has a industrial controller called MH1, this controller can control up to 64 axes. Is there a cRIO that can do the same?

I am thinking of use a rate of the position setpoint for each axis of 100Hz.

The cRIO-9042 is capable to 4ms, in other words, can I use the position rate setpoints at 250Hz for all the 20 axes?

I will also need to read 20 analog sensors, (+-10V input), they will be my feedback control.

[Karl-G · Accepted solution]

At a slow enough scan engine period, the highest end cRIO CPU (which the 9042 uses) should be able to 64 axes. However, most EtherCAT Drives have a practical upper limit to the period for receiving setpoints in CSP mode. The Delta has been tested at 5ms, and the Kollmorgen AKD will go as slow as 8ms. At 8-10ms, the cRIO-9042 should be able to control 64 axes, again depending on what other processing the controller needs to do.

Delta's MH1 controller is fairly different from a CompactRIO (it's more like an industrial PC), but for any vendor, it is just a matter of CPU performance and API flexibility. SoftMotion provides the best motion API in LabVIEW RT.

Yes, you can control the position setpoints sent to the EtherCAT drives at the Scan Engine period, so every 4ms to each of the 20 drives if using the cRIO-9042. By default, SoftMotion moves will not use external feedback to influence the trajectory generation on the fly. You will need to perform your own trajectory generation on the fly to modify individual setpoints programmatically if you want to use analog data such as your sensors.