servo feedback loop

[bdrmachine]

I have a general question I help one of you knowledgeable members can clear up of me.

If I was to use a Mesa 5I20 pci card to control a servo motor with a attached opto-encoder, using a Granite servo driver and EMC2 what is the feed back loop. It appears that the encoder connects to the Granite driver only, so how is the position verified by emc. Is all the PID function handled on the servo driver with emc and the 5I20 only passing signals to the driver in hopes it does the correct commanded move?

Thanks
Brian

[keebler303]

I don't have experience with that specific hardware but in general you will use the drive in "torque mode" or "current mode" and all of the tuning and PID calculations will occur in the control. I believe the Granite Devices drives can be configured to run in torque mode with an analog command signal.

You could also use the Granite drive in position mode and then no PID or tuning is done in the control. It really depends on what you want.

Matt

[PCW_MESA]

I have a general question I help one of you knowledgeable members can clear up of me.

If I was to use a Mesa 5I20 pci card to control a servo motor with a attached opto-encoder, using a Granite servo driver and EMC2 what is the feed back loop. It appears that the encoder connects to the Granite driver only, so how is the position verified by emc. Is all the PID function handled on the servo driver with emc and the 5I20 only passing signals to the driver in hopes it does the correct commanded move?

Thanks
Brian

There are at least a couple of options:

1. Is to run the Granite drives in step/dir mode, no feedback required, however you could Y the encoder signals back to the 5I20 to monitor the following error if you wanted to. The 5I20 can generate MHz step rates so there no problem getting to full speed with full encoder resolution.

2. Is to run the Granite drives in PWM mode (PWM from 5I20 sets the torque) and run the encoders back to the 5I20 (or Y them if the Granite drive requires the encoder signals for commutation if its a AC servo) In this case EMC runs the PID position loop