Tuning The Closed Loop Controller; Manual Pid Adjustment - Danfoss VLT AQUA Drive FC 202 Design Manual

Introduction

2.8.10 Tuning the Closed Loop Controller

Once the closed loop controller has been set up, test the
performance of the controller. In many cases, its
performance is acceptable using the default values of
20-93 PID Proportional Gain and 20-94 PID Integral Time.
However, in some cases it is helpful to optimise these
parameter values to provide faster system response while
still controlling speed overshoot.

2.8.11 Manual PID Adjustment

1. Start the motor
2. Set 20-93 PID Proportional Gain to 0.3 and
increase it until the feedback signal begins to
oscillate. If necessary, start and stop the
frequency converter or make step changes in the
set-point reference to attempt to cause
oscillation. Next reduce the PID Proportional Gain
until the feedback signal stabilises. Then reduce
the proportional gain by 40–60%.
3. Set 20-94 PID Integral Time to 20 s. and reduce it
until the feedback signal begins to oscillate. If
necessary, start and stop the frequency converter
or make step changes in the set-point reference
to attempt to cause oscillation. Next, increase the
PID Integral Time until the feedback signal
stabilises. Then increase of the Integral Time by
15–50%.
4. Use 20-95 PID Differentiation Time only for fast-
acting systems. The typical value is 25% of
20-94 PID Integral Time. Use the differential
function only when the setting of the propor-
tional gain and the integral time has been fully
optimised. Make sure that oscillations of the
feedback signal are sufficiently dampened by the
low-pass filter for the feedback signal
(6-16 Terminal 53 Filter Time Constant,
6-26 Terminal 54 Filter Time Constant, 5-54 Pulse
Filter Time Constant #29 or 5-59 Pulse Filter Time
Constant #33 as required).
®
VLT AQUA Drive FC 202 Design Guide
®
MG20Z102 - VLT is a registered Danfoss trademark
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