GE Industrial Solutions 6KCV300WPD User Manual

Page 154

GEL100340

s p e e d o b s

AccFFwd

speedobs

Speed

›-

Description

SPEED

estimates Speed [x] and acceleration

from measured speed (MeasSpd

using a algorithm with two time constants: Taul[sec] and

is the sample time of the control.

Here [x] is the unit of the measured speed.

It can be used to estimate motor angular speed and motor angular acceleration from motor speed coming from
a tachometer or encoder. Motor speed is filtered to output estimated motor speed, and derivate to output
estimated motor acceleration. Estimated motor acceleration can be used to determine current feed-forward to
drive the motor faster.

AccFFwd

is used by observer to obtain a better speed and acceleration estimation. If no feed-forward

of acceleration is

this input can be leave zero.

Let us make a simple example:
Consider a machine that manufactures a material. This machine has two motors using to move material, one is
the master and other is the slave. Slave drive can read master encoder and a digital signal from master that
indicates when master is acceleration (this signal can come from master ramp function). Slave can use

speedobs block to estimate line speed and acceleration. So

[rpm] is master speed from its encoder,

AccFFwd is calculated as follows:

if (master is acceleration)

AccFFwd=SlaveAcc;

else

So speedobs block can use this information (AccFFwd) to obtain a better speed and acceleration estimations.
The resulting Speed obtained from speedobs can use to calculate slave speed reference, and

can use as

slave current feed-forward (after appropriate scaling depending on master

ramp times, master and

slave gear-box ratios and slave motor inertia) to improve slave response at master ramp acceleration.
As explained above, AccFFwd can leave zero but speed and acceleration would be estimated with a delay.

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