[etherlab-users] Is Ethercat Master Enough to Control Servo

[Thomas Nelson]

On Sep 5, 2012, at 2:13 AM, Raz Ben Yehuda wrote:

> On Sun, 2012-09-02 at 11:47 +0200, takeshi ikeya wrote:
>> Hi Tahir!
>> I think ENOUGH..
>> If you need quick response, you'd beter use it under RTAI (Linux).
>> 
> I must add that did not find the current design suitable for moving
> servo drives. For this reason I modified etherlab to support slave DC
> bus time ( currently etherlab is App time based).
> 
>> 
>>  takeshi.ikeya at gmail.com
> 
> -- 
> https://sites.google.com/site/ironspeedlinux/


I have to disagree with these blanket assessments.  Much is dependent on the hardware/software platform that the Etherlab EtherCAT installation is deployed on, and this must be taken into consideration to realistically assess what the resulting system is capable of.

In my case, I have a client that is successfully operating two Copley AE2 dual axis servo drives in a high-precision robotics system at a 250 uS cycle time (4 KHz) on an 1.6 GHz Intel Atom N270 with a 82574L Gb master interface under Linux 3.2.28-rt42 (RT_PREEMPT).  Jitter is < 10 uS even with the system performing other non-RT tasks, such as the network service for the remote application control/status UI.

Using RTAI or Xenomai was out of the question because we needed to use off-the-shelf industrial x86 SBCs and only the mainline kernels have the HW support required.

Tom Nelson
Consulting Engineer
Granite Computer Sciences, LLC
Milford, NH USA

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