Velocity - Controller Structure
Function description 89
Version: 1.5
20.1.5.4 Description of IDN P-0-0514
Mode
Default value: 1 Basic Observer
Here you can choose between the following settings:
• 0: Off = Velocity Observer not active
• 1: = Basic Velocity Observer active in basic mode (3rd order)
• 2: = Advanced Velocity Observer active in advanced mode (5th order) (from firmware 2.10)
Bandwidth
Default value: 500 Hz
Here you can set the bandwidth of the Velocity Observer. The filter effect can be intensified by reducing the
bandwidth. Increasing the bandwidth reduces the filter effect. At low bandwidth the speed signal is very
smooth, although in this case any interference takes longer to compensate.
A higher bandwidth enables faster correction of faults. The associated higher bandwidth of the velocity
controller causes a larger current ripple.
The basic rule:
The higher the resolution and quality of the motor feedback system used, the higher the bandwidth can be
set.
Correction factor lq to ACC
Default value: 1
If the moment of inertia for the motor and the load is set correctly in P-0-0071 or P-0-0127 (only for linear
motors), the Observer can correctly calculate the axis acceleration from the measured current value:
The Observer uses the table M = M(i) stored in P-0-0074.
Note
Torque/current characteristic curve P-0-0074
Further information about the torque/current characteristic curve P-0-0074 can be found in
chapter: „Torque (force) controller structure [
}77]“ of this function manual.
The equation indicates that the calculated acceleration value is too large if the value for J
load
is too small and
vice versa. Depending on the load and coupling type between motor and load, part of the load may become
decoupled at frequencies above the Observer bandwidth and may then no longer be active. The "Correction
factor" can be increased, in order to compensate this. The value for the full moment of inertia of the load is
also required for the acceleration pre-control [
}15] and should therefore be entered as precisely as possible.
If the acceleration pre-control [
}15] was enabled, the correct value for the moment of inertia can be
determined. It is the value at which the pre-control works perfectly with the 100% setting. The optimum value
for the "Correction factor Iq / Acc" can be determined using a Bode diagram for the velocity controller.
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