The following basic settings can be used in most
applications with a 1024 PPR encoder connected directly
to the motor shaft and maximum reference (
3-03 Maximum
Reference
) is 1500 RPM:
32-60 Proportional factor
= 200
32-61 Derivative factor
= 1000
32-62 Integral factor
= 5
32-65 Velocity Feed-Forward
= 10200
Velocity Feed-forward (
32-65 Velocity Feed-Forward
) can
also be calculated using the following formula:
Velocity Feed forward =
62914560000
envel × eres × tsample
Where:
-
“envel” is encoder velocity in RPM at maximum
reference (
3-03 Maximum Reference
).
-
eres” is the encoder resolution
(Incremental encoder: eres =
32-01 Incremental
Resolution
* 4.
Absolute encoder: eres =
32-03 Absolute
Resolution
).
-
“tsample” is PID sample time
(tsample =
32-69 Sampling Time for PID Control
except with SYNCV where tsample =
32-70 Scan
Time for Profile Generator
).
The sample program “Feed-forward calculation” is making
the above calculation and sets the parameters:
3.6.1 Sample Program: Feed-forward
Calculation
This program calculates basic settings for Velocity Feed-
forward and PID settings based on the following inputs:
Encoder type (
32-00 Incremental Signal Type
and
32-02 Absolute Protocol
), Encoder resolution
(
32-01 Incremental Resolution
or
32-03 Absolute Resolution
),
Encoder velocity (par. 19-00), and Motion type (par. 19-00).
These parameters must thus be set before starting the
calculation.
The program performs the following steps when setting
input 1:
1.
Check encoder type and resolution
2.
Calculate PID sample time in order to get
sufficient resolution
3.
Check motion type and select sample time
4.
Calculate Feed-Forward.
Parameters are updated when setting input 2.
The updated parameters can be saved by setting input 3.
New calculation is enabled by setting input 4.
3.6.2 Influence to the Control Loop when
Changing Parameters
The gain of the control loop changes when one or more of
the following parameters is changed: Maximum reference,
encoder resolution, and gearing between motor and
encoder.
When changing these parameters the following rules
apply:
Increased maximum reference = P and D factors as well as
Feed-forward must be reduced.
Higher encoder resolution = P and D factors as well as
Feed-forward must be reduced.
Increase gear-ratio between motor and encoder (encoder
turning slower) = P and D factors as well as Feedforward
must be increased.
How to Install
MCO 305 Operating Instructions
MG.33.K3.02 - VLT
®
is a registered Danfoss trademark
17
3
3
