Tuning Kinetix 6000 Drives

I have an application that I am trying to tune. The Kinetix 6000 drive is setup as a position servo and I am trying to tune the drive. I am monitoring the position command and the position feedback and the graphs are laying on top of each other with very little error. So, I feel the position loop is tuned optimally. Now, when I trend the velocity command vs the velocity feedback, I see alot of error. I have attempted to tune the speed loop with the velocity prop/integral and I see no effect on the velocity profile. Here are my tuning parameters that I have. Position P= 200, I=1, Velocity P=1100, I=0 Feedforward Vel and Accel = 85%

I have a controllogix plc that has V18 in it and the drives have firmware 1.116 which all are the latest and greatest from AB.

Please give some suggestions on why I can't seem to make the velocity loop respond to my tuning. Thanks.

What you say doesn't make sense

How can the position be tuned and not the velocity? The velocity is just the derivative of the position. The position and velocity are not independent. One thing you must remember is that a small error in position will look like a much larger error in velocity. Why? Think about it.

Like I said, I plotted the pos command and pos feedback and they were almost one line.. So, the position is following with little error. I plot the vel command and vel feedback and there is alot of error. The lines don't lay on top of each other. In AB Software, there are position tuning parameters as well as speed.

More Information Needed

What Model PLC are you using? What is the motor and the Kinetix 6000 amplifier?

Do you have at least the Lite RSLogix version? (Autotune is available)
RSLogix 5000 ordering info

Why are you not using the AutoTune? - I usually get reasonable results unless you have an inertia mismatch, then a lot more work is required.

A little more information on your application please - are you after a fast settling time with Position Accuracy, or is the axis following a master Axis (ie Gearing) (Peter will probably have a go at me about this). Is the axis rotary or linear (do you have travel limits)

Also your Accel and Velocity Feedforward are not at the typical values of 100% or 0% - You are using values that I have never had to use with Kinetix

Change your Trend to look at AxisName.PositionError and do the following to get the update
1) Enable the "Auto Tag Update" in the motion group properties
2) in the axis properties -> Drive/Motor->"Real Time Axis Information" select "position error"

Actually, firmware version 1.118 is available. I also use 100% feed forwards and change the velocity proportinal gain by half after autotuning.

change the velocity proportinal gain by half after autotuning.

Click to expand...

I used to do that until a Rockwell engineer gave me a tip on the autotune damping factor.
I have found it better to Autotune with Damping factor of 1.0 (default is 0.8)
This means that the autotune calculates gains for a critically damped response instead of underdamped which in many cases is too much.