PIV Tuning: Applying the Position Loop Integral (Kip)

PIV Tuning:
Applying the Position Loop Integral (Kip)

The basic idea behind tuning the position loop integral is to turn it up until you see some overshoot in the position error. In the plots below, we will be looking for overshoot in the position error (white). Our goal is to turn up Kip as much as possible without any overshoot.

Start with a Kip of 0.001 for low to medium resolution systems. Use a Kip of 0.000 01 for high resolution systems. Command the same motion from tuning the position gain.

1,000 count move 50,000 count / sec velocity 300,000 count / sec²	Red - Command Position Yellow - Actual Position White - Position Error
Kpv = 5,000 Ka1 = 0.7 Kpp = 0.001 VintMax = 32767 Kip = 0.001

We will turn up Kip until we see overshoot on the position error that is acceptable or see other unacceptable behavior (noise). Turn up Kip in increments (~200%) until you find this limit. The following figures show the progress from a very small Kip (0.001) to the Kip value where instability sets in (0.4). At that point, turn down Kip for a margin of stability.

1,000 count move 50,000 count / sec velocity 300,000 count / sec²	Red - Command Position Yellow - Actual Position White - Position Error
Kpv = 5,000 Ka1 = 0.7 Kpp = 0.001 VintMax = 32767 Kip = 0.001

Turning up Kip shows no improvement over position error.

1,000 count move 50,000 count / sec velocity 300,000 count / sec²	Red - Command Position Yellow - Actual Position White - Position Error
Kpv = 5,000 Ka1 = 0.7 Kpp = 0.001 VintMax = 32767 Kip = 0.1

In this case, we are not able to reduce position error with Kip. If the system does not meet its performance requirements, please refer to the Feedforward Tuning section for additional information.

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