NordicCNC's build log

[jarjar]

I'd be interested in hearing how you get on with tuning. What controller and which method of control +/-10v or Step/Dir .?

Step/Dir is the most reliable and flexible. With analog +10V you're forced to control the servo in velocity mode.
With Step/Dir you can control it in position or velocity mode.
I'm also convinced position mode (letting the drive close all the loops internally) is the best way since the drive can do it much faster than the controller.

What hassle.? Far less wiring and setting up far as I can tell, esp if using Bus type.! . . . I've not used any yet but soon will be doing so I'll let you know.

The interface of the servo drive is a whole other topic and has nothing to do with absolute encoders. For absolute encoders you need to connect a battery and 2 extra wires to request the position data when using the standard analog/pulse-train drives. And as I said above, the controller needs to be able to read the position data for the specific servo manufacturer.

Now if you use EtherCAT drives, indeed you just need a RJ-45 cable between the drive and controller (but still need the battery). But you have 2 more problems:
- you need to actually find one of those rare EtherCat drives. Yaskawa for example doesn't sell them in the Chinese market. So you would need to go through an official reseller and pay $$$, or buy another brand: Omron / Panasonic / Mitsubishi / Delta / Estun...
- be prepared to spend weeks and write some C to make the controller talk to the drive (LinuxCNC in this case, the only one supporting EtherCAT).

[JAZZCNC]

Step/Dir is the most reliable and flexible. With analog +10V you're forced to control the servo in velocity mode.
With Step/Dir you can control it in position or velocity mode.
I'm also convinced position mode (letting the drive close all the loops internally) is the best way since the drive can do it much faster than the controller.

I agree about step/dir being simpler when drives handle position but not so sure that it's easier when your closing the loop back to the controller. Analog gives a little more control is my experience. But that said, my experience with servo's isn't massive and mostly with full closed-loop Analog controllers.

The interface of the servo drive is a whole other topic and has nothing to do with absolute encoders. For absolute encoders you need to connect a battery and 2 extra wires to request the position data when using the standard analog/pulse-train drives. And as I said above, the controller needs to be able to read the position data for the specific servo manufacturer.

Now if you use EtherCAT drives, indeed you just need a RJ-45 cable between the drive and controller (but still need the battery). But you have 2 more problems:
- you need to actually find one of those rare EtherCat drives. Yaskawa for example doesn't sell them in the Chinese market. So you would need to go through an official reseller and pay $$$, or buy another brand: Omron / Panasonic / Mitsubishi / Delta / Estun...
- be prepared to spend weeks and write some C to make the controller talk to the drive (LinuxCNC in this case, the only one supporting EtherCAT).

To be honest I think we are getting crossed wires a little here.! I know exactly what's involved with interfacing drives and wiring Absolute encoders etc.
My point was there's no more hassle using Absolute than incremental and there's actually less wiring required because you're not fitting home switches etc. Also if your using EtherCat or Bus type then there's even less wiring involved and less tuning involved because the controller and drives work closely together.

Also, I wasn't talking about Yaskawa Ethercat or trying to make Ethercat work with Linux or any other DIY controller. I'll be using an industrial Bus type controller with matched drives so i won't be needing to write any code etc.! . . . How long it takes to get up and running however will remain to be seen... .Lol

[jarjar]

My point was there's no more hassle using Absolute than incremental and there's actually less wiring required because you're not fitting home switches etc.

You still need a homing switch to setup the absolute encoder reference. The only difference is that you don't need to home on subsequent power ups.

[JAZZCNC]

You still need a homing switch to setup the absolute encoder reference. The only difference is that you don't need to home on subsequent power ups.

Been told doesn't need a physical switch the system just needs to be calibrated with encoder offset for the home position which can be obtained through software..! . . . I will find out soon enough.