Position or torque mode?

[rforney]

I am currently setting up a DMC 4080 to interface with Yaskawa sigma-5 servos.  I have the choice of Velocity, Torque, or position (step and dir) control.  I have been told that velocity control mode will be the worse, since the drives have features that will try to tune the servo as well.  I have hear that torque control should work, as many of the drives' features are disabled in this mode.  I do also have the capability of using position control.  This would allow some of the drives features to make the system better.
I have hooked up the drives using velocity and torque mode. The torque mode appeared to be the most stable, but remember, I have little experience with the galil and tuning in general.  This was also without any load applied.

So, what method of control do you guys think would have the most merit?

Thanks,

Rob

[kcrouch]

I use the Galil with Yaskawa drives in torque mode. Just need to tune it well.
Kenny

[rforney]

Kenny,

Do you have any videos of your machine running online?  I am still wondering if this control setup can handle what I want it to do (fast 3D carving, with rapid direction changes on the Z axis all the time).

Cheers!

Rob

[kcrouch]

I don't have any video, but we use Galil and Mach for everything from sign carving to lathe turning. You should have no trouble at all with rapid Z moves.
Kenny

[rforney]

Thank you for the info, Kenny.  I am finalizing the wiring right now.  Servo's sound good after autotuning, and galil can make them move nicely.  Once I get my network sorted out, I will let Mach have a shot at it.

Do you use contour mode (the galil plugin setting) on any of your machines? 

Once all of this is set up, I would like to post all my settings and wiring stuff to share with everyone.  Problem is, it is not right just yet...

Thanks,

Rob

[smurph]

You can try Contour mode. It was specifically designed for the Accelera controllers.  But it has not been tested as much as the Linear Interpolation mode.  LI will work fine.

Steve

[rforney]

Wow.  Tuning servos does not accidentally happen. 

I managed to get a stable response, until I hood the gearboxes up to the rack.  What a nasty noise.  The autotuning button is pretty neat.  I wish it would tune the servos for me.

Seeing how I have no real experience tuning servos, I am going to attempt step and direction mode, and see how that goes.  This is what the Yaskawa dealer wanted me to do all along, and the drives have auto-tuning features that should make life easier.

Wish me luck!

Rob

[rforney]

So,

In position mode, this machine can really move out!  Yaskawa sigma 5 drives do an excellent job of tuning the servos, just like the dealer said.

However...

When configured in stepper mode, some funny things happen.  I believe that mach is issuing a GA command to axis D.  This is fine, but it is gearing off of the main encoder input.  Because of the electronic gearing that I am using in the drives, this will not work.  The second X axis (axis D) is moving about 7 times as fast as the first one.  Is there a way I can program mach to tell the Galil to gear the D axis to the auxillary encoder input of A?  I must emphasize that Galil has no problems moving these individually, and accurately.

Attached is an image from galil tools after a jog was commanded from mach. I jogged both x axis' in mach (A and D), then opened up the terminal.  After dividing the D axis encoder position by the A axis encoder position, I came up with 6.8619436.  This is the distance traveled with one pinion revolution.  I have the drive's gearing set to 10000 pulses = 1 inch.  This is working great for the A axis, B axis, and C axis.  The D axis works fine when commanded from galil.  But when Mach tries to drive that axis, it runs a good bit faster.

I believe if I can gear the position of D to the aux encoder of A, all will be well.  Anyone know how to do this through mach?

[rforney]

Well, correction to that.

GA,,,CA seems to fix the problem.  I would like to have the plugin input that for me.  How do I set that?

Rob

[smurph]

Make a file called GalilInit.txt, put your GA,,,CA command in it, and place the file in the plugins directory.  When the plugin initializes the Galil, it will send the contents of that file to the controller.  You can put more than one command in that file if needed.  One command per line.

BTW, if you think position mode is fast, try velocity or torque mode.  The full version of Galil Tools provides a tuning function for the servos.  It will get you in the ball park.  Well worth the price of admission if you have never tuned servos before.

Steve