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Submitted by IanPMI on Thu, 10/02/2014 - 07:45

Hello everyone,

I am currently attempting to tune a linear stage with Torque Control using the Velocity Zone Method described in Note5491. However, I am seeing an issue with my velocity graph when I attempt to tune my stage.

According to steps 2-7, I have increased the values of KD and FV on the axis to the point where I can reach the desired velocity I have provided to the controller. However, once the stage reaches that velocity, instead of maintaining the desired velocity curve shown by the encoder reference, the velocity tapers off and slows down. I have provided a very minimal KP (0.1) as mentioned in previous posts, but it doesn't seem to help. Any reason why my stage cannot maintain the desired velocity once it reaches it?

-Ian

Comments 2

IanPMI on 10/02/2014 - 08:08

I can also supply a screenshot of what my graphs look like if you want a better idea of what I'm seeing. This forum doesn't allow me to post it, apparently.

Galil_CoryB on 10/21/2014 - 10:12

IanPMI-

Please see your other post for details on FV and FA.

In short:
FV will provide an open loop offset when slewing.
FA will provide an open loop offset while accelerating/decelerating.

With a constant FV/FA, the open loop offset will be proportional to the profiled velocity or accel/decel respectively.