To tune a velocity mode amplifier you will typically have a very low KD value and higher KP and KI values for similar mechanics.

The same basic principles apply in how to manually tune a system using velocity mode amplifiers to that of current mode amplifiers. Details of this procedure can be found on the below link.
http://www.galilmc.com/support/appnotes/optima/note3413.pdf

One thing that we have found useful in tuning systems using velocity mode amplifiers is the FV command. The FV command is an open loop offset that is proportional to the commanded velocity. See the FV command in the command reference for more information.

Typically it is a little more difficult to tune a velocity mode amplifier.

Hi Andy

Thanks for your reply.

I still messed up the term of Velocity Mode and Current/Torque Mode.

The supplier told us that the Torque Mode is not for the movements of CNC Milling machine. Do you think that can the Torque Mode be configued for CNC Machine positioning movements? My CNC controller has a +/- 10V analogue signal output for servo driver.

With best regards

Tim

Torque mode is ideal for positioning movements. The advantage of running an amplifier in velocity mode is when your application calls for a constant speed with low velocity ripple. Typically during point to point moves, or positioning movements, holding a constant and perfect velocity through the move is not critical. What is critical is maintaining and holding position at the end points. In most applications this is easier to tune with an amplifier in Torque mode.

Either way, if you tune get the system tuned properly, an amplifier in torque mode or velocity mode should give you similar performance.

Hi Andy

The Servo Motor could spinned now by using Torque Mode. However, we still have the following problems:

1) The motor spinning was not smooth but slighly "vibrate" or sluggish.
The the spinning coordination of motor was correct.

2) The servo-amplifier was bing driven by about +3-4 volt analogue signal. With this voltage, the motor was over-speeded.

If this voltage signal for Velocity-Mode, the motor will spin at high speed smoothly.

If only about +1 volt used the Torque Mode, the spinning speed was very slow.

My impression was the same paramters of Torque seems different outcomes from Velocity Mode even the paramters for both Mode are same.

You have any ideas how to solve the problem?

Regards

Tim

You have to re-tune when you are in torque mode, see the app note referenced above on tuning. The ideal tuning parameters will be different with an amplifier in torque mode from an amplifier in velocity mode.

When the amplifier is in velocity mode, the torque output from the Galil is going to command a velocity to the motor. When the amplifier is in torque mode, the torque output from the Galil represents current or torque to the motor. The command outputs will very greatly in both cases.

Hi Andy

Since I never use Torque Mode of Servo Motor for CNC Milling Macine's movements of XY table. For the time being, I still could not get the good results from turning. Under Torque Mode, the motor spinning vibrating and not smooth at all. One CNC machine expect told us that Torque Mode is not for CNC Milling Machine as under the Torque Mode, the accel, deccel speed and velocity could not be controled, and the movements were not smooth at all. I shoud use Velocity Mode but not the Torque Mode.

Do you agree with that?

Regards

Tim

The Galil controller can control acceleration, deceleration speed and velocity for a system in which the amplifier is in torque or velocity mode; assuming and that the motor has been sized correctly and the system is properly tuned. So in that respect I do not agree.

But, if your system is running better when the amplifier is in Velocity mode, then run the amplifier in Velocity mode.