Pid Control; Speed Pid Control - Danfoss VLT FC 360 Design Manual

Product Overview

2.5 PID Control

2.5.1 Speed PID Control

2 2
1-00 Configuration Mode
[0] Speed open loop
[1] Speed closed loop
[2] Torque
[3] Process
Table 2.3 Control Configurations, Active Speed Control
"N.A." means that the specific mode is not available at all. "Not Active" means that the specific mode is available but the Speed Control is not
active in that mode.
The following parameters are relevant for the Speed Control:
Parameter
7-00 Speed PID Feedback Source Select from which input the Speed PID should get its feedback.
7-02 Speed PID Proportional Gain The higher the value - the quicker the control. However, too high value may lead to oscillations.
7-03 Speed PID Integral Time
7-04 Speed PID Differentiation
Time
7-05 Speed PID Diff. Gain Limit
7-06 Speed PID Lowpass Filter
Time
Table 2.4 Speed Control Parameters
24
®
VLT AutomationDrive FC 360 Design Guide
1-01 Motor Control Principle
U/f
Not Active
N.A.
N.A.
Not Active
Description of function
Eliminates steady state speed error. Lower value means quicker reaction. However, too low value may
lead to oscillations.
Provides a gain proportional to the rate of change of the feedback. A setting of zero disables the
differentiator.
If there are quick changes in reference or feedback in a given application - which means that the error
changes swiftly - the differentiator may soon become too dominant. This is because it reacts to
changes in the error. The quicker the error changes, the stronger the differentiator gain is. The differ-
entiator gain can thus be limited to allow setting of the reasonable differentiation time for slow
changes and a suitably quick gain for quick changes.
A low-pass filter that dampens oscillations on the feedback signal and improves steady state
performance. However, too large filter time will deteriorate the dynamic performance of the Speed PID
control.
Practical settings of parameter 7-06 taken from the number of pulses per revolution on from encoder
(PPR):
Encoder PPR
512
1024
2048
4096
®
MG06B202 - VLT is a registered Danfoss trademark
plus
VVC
Not Active
ACTIVE
Not Active
Not Active
7-06 Speed PID Lowpass Filter
Time
10 ms
5 ms
2 ms
1 ms