Predictors - SSD Parvex DIGIVEX Little Drive Servoamplifier User And Commissioning Manual

DIGIVEX Little Drive Servoamplifier
Second order filter
This phenomenon cannot be dealt with by P/PI/PI 2 adjustment. If the resonance cannot be dealt
with mechanically, the frequencies concerned must be eliminated. This is the function of the
second order low pass filter.

6.1.6 Predictors

Purpose of predictors
Four physical phenomena:
Vertical mass.
Dry friction
Friction proportional to speed.
Acceleration.
Are direct and calculable causes of modification of motor torque.
The purpose of the predictors is, by calculation, to act directly on the current set point, without
recourse to the speed loop and without waiting for the speed error produced by these
phenomena (see block diagram).
The principle of predictor setting and work is to minimize the current set point part from the P, PI,
2
PI branch and therefore to reduce the speed error.
As these predictors are outside the speed loop (which must be adjusted first), they do not affect
stability. They provide an appreciable improvement on response time.
The acceleration predictor improves stability and allows gain to be increased in any position loop
superimposed on the speed loop.
However, it should be noticed that many speed servocontrols do not require the use of these
predictors.
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PVD 3530 GB 01/2005
Diggb17.D/pl35.W