Sample Program: Feed-Forward Calculation; Influence To The Control Loop When Changing Parameters - Danfoss MCO 305 Operating Instructions Manual

How to Install
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
32-61 Derivative factor
32-62 Integral factor
32-65 Velocity Feed-Forward
Velocity Feed-forward (32-65 Velocity Feed-Forward) can
also be calculated using the following formula:
62914560000
Velocity Feed forward =
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:
MCO 305 Operating Instructions
3.6.1 Sample Program: Feed-forward
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
= 200
32-02 Absolute Protocol), Encoder resolution
= 1000
(32-01 Incremental Resolution or 32-03 Absolute Resolution),
= 5
Encoder velocity (par. 19-00), and Motion type (par. 19-00).
= 10200
These parameters must thus be set before starting the
calculation.
The program performs the following steps when setting
input 1:
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
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.
®
MG.33.K3.02 - VLT is a registered Danfoss trademark
Calculation
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.
Changing Parameters
3 3
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