EMC and servos

[RP Designs]

So I have been doing a little bit of reading through the EMC documentation but I haven't really found an answer. The documentation basically addresses stepper configuration through the stepconf wizard but it doesn't really have any set-up information with regards to servo set-up. I am still very new to this so maybe the software portion is the same and everything is sorted in the drivers, but how do you set up a servo?

[chester88]

I assume you mean how do you set up servos software wise.
First currently there is no configuration wizard like Stepconf for servos.
So you would probably find a servo sample configuration that is close to what you want a tweak it.
The one you choose is mostly dependent on what type of I/O card you want to use.
As far as Tuning the sevo loop EMC uses PID with feed forward ability. You have to tune ther parameters by hand, though The AXIS GUI makes this easier to do.
PID tuning is a large subject on it's own.
Do you have more specific Questions?

[RP Designs]

Originally Posted by chester88 I assume you mean how do you set up servos software wise. First currently there is no configuration wizard like Stepconf for servos. So you would probably find a servo sample configuration that is close to what you want a tweak it. The one you choose is mostly dependent on what type of I/O card you want to use. As far as Tuning the sevo loop EMC uses PID with feed forward ability. You have to tune ther parameters by hand, though The AXIS GUI makes this easier to do. PID tuning is a large subject on it's own. Do you have more specific Questions?

Well I guess my question is more like setting up servo's with a clean sheet of paper approach. If I where to set up a 4 axis mill and wanted to set up three axis with servos and encoder feedback and a 4th axis with steppers, how would I go about doing that in the software. The documentation for he stepper set-up seems pretty straight forward, but the servo set-up doesn't seem to be documented at all! i would like to see a servo set-up written step by step if possible just to get a feel of what needs to be done. Maybe it exists but I certainly haven't stumbled across it yet. i also want to see what sets EMC apart from Mach software, especially in the reals mof servos and closed loop controls.

[chester88]

Originally Posted by RP Designs Well I guess my question is more like setting up servo's with a clean sheet of paper approach. If I where to set up a 4 axis mill and wanted to set up three axis with servos and encoder feedback and a 4th axis with steppers, how would I go about doing that in the software.

Well as I said that depends on what hardware you have.
Yes I agree there is no complete step by step write up about servos.
but by looking at a sample config and reading the manual/Wiki or asking on the EMC mail list you can figure it out.
In the end you could be the one to write a page in the wiki about it

As for EMC vrs Mach
The first thing is EMC can close the servo loop, as far as I know Mach cannot.
Mach can use servos drivers that use step / direction signals but that is not the same thing.
Mach is easier / more intuitive to set up - EMC is more flexible.
Mach costs you money - EMC costs time.

[jmelson]

Originally Posted by RP Designs Well I guess my question is more like setting up servo's with a clean sheet of paper approach. If I where to set up a 4 axis mill and wanted to set up three axis with servos and encoder feedback and a 4th axis with steppers, how would I go about doing that in the software. The documentation for he stepper set-up seems pretty straight forward, but the servo set-up doesn't seem to be documented at all! i would like to see a servo set-up written step by step if possible just to get a feel of what needs to be done. Maybe it exists but I certainly haven't stumbled across it yet. i also want to see what sets EMC apart from Mach software, especially in the reals mof servos and closed loop controls.

OK, first you need to decide on a servo interface device. There are now a dizzying variety of products available. You CAN, in theory, rig up servos with software encoder counting, and either software PWM or step-direction drive. This requires extra parallel ports, and loses some of the advantages of servos, such as high encoder resolution WITH high velocities. At some point, the software can't keep up with the step or encoder count rates.

Once you have chosen a servo interface unit, you can select a sample configuration file from the menu and customize from there. A number of sample files, including for my boards (Pico Systems) are included with EMC2.

Jon