Tuning Pid Speed Control; Process Pid Control - Danfoss VLT AutomationDrive FC 301 Series Design Manual

Basic Operating Principles

3.6.6.2 Tuning PID speed control

The following tuning guidelines are relevant when using
one of the Flux motor control principles in applications
where the load is mainly inertial (with a low amount of
friction).
The value of 30-83 Speed PID Proportional Gain is
dependent on the combined inertia of the motor and load,
and the selected bandwidth can be calculated using the
following formula:
Total inertia kgm 2 x par . 1 − 25
Par . 7 − 02 =
Par . 1 − 20 x 9550
NOTICE!
1-20 Motor Power [kW] is the motor power in [kW]
(i.e., enter '4' kW instead of '4000' W in the formula).
A practical value for the bandwidth is 20 rad/s. Check the
result of the 7-02 Speed PID Proportional Gain calculation
against the following formula (not required when using a
high-resolution feedback such as a SinCos feedback):
x 4 x Encoder Resolution x Par . 7 − 06
0.01
Par . 7 − 02 MAX =
2
Max torque ripple %
The recommended start value for 7-06 Speed PID Lowpass
Filter Time is 5 ms (lower encoder resolution calls for a
higher filter value). Typically, a max torque ripple of 3% is
acceptable. For incremental encoders, the encoder
resolution is found in either 5-70 Term 32/33 Pulses per
Revolution (24 V HTL on standard adjustable frequency
drive) or 17-11 Resolution (PPR) (5 V TTL on Encoder Option
MCB 102).
Generally, the practical maximum limit of 7-02 Speed PID
Proportional Gain is determined by the encoder resolution
and the feedback filter time, but other factors in the
application might limit the 7-02 Speed PID Proportional Gain
to a lower value.
To minimize the overshoot, 7-03 Speed PID Integral Time
could be set to approx. 2.5 s (varies with the application).
Set 7-04 Speed PID Differentiation Time to 0 until everything
else is tuned. If necessary, finish the tuning by experi-
menting with small increments of this setting.
MG33BF22
Design Guide
x Bandwidth rad / s
x
x π
Rev. 2014-04-04 All rights reserved.

3.6.6.3 Process PID Control

Use the Process PID Control to control application
parameters that can be measured by a sensor (i.e.,
pressure, temperature, flow) and be affected by the
connected motor through a pump, fan or otherwise.
Table 3.4 shows the control configurations where the
process control is possible. When a flux vector motor
control principle is used, take care also to tune the speed
control PID parameters. Refer to chapter 3.6 Controls to see
where the speed control is active.
1-00 Configu- 1-01 Motor Control Principle
ration Mode
U/f
VVC plus
[3] Process Not Process
Active
Table 3.4 Control Configurations with Process Control
NOTICE!
The Process Control PID works under the default
parameter setting, but tuning the parameters is highly
recommended to optimize the application control
performance. The two Flux motor control principles are
specially dependant on proper Speed Control PID tuning
(before tuning the Process Control PID) to yield their full
potential.
3
Flux Flux w/
Sensorless enc. feedb
Process & Process &
Speed Speed
27
3