BECKHOFF AX2000 - Manual (Page 7)

III.4 Optimizing the speed controller
ò
ò
ò
ò
ò
ò
ò
SETP. -OFFSET:
Leave the amplifier enabled. If the axis is drifting, alter the parameter SW-Offset until
it stands still (or use the function AUTO-OFFSET).
SETP. RAMP +/-:
The setpoint ramps are used to smooth the setpoint input (filter effect).
Set the mechanical time constant for the complete system, i.e the rise time for the
speed from 0 to n
cmd
.
As long as the ramps that are set are shorter than the mechanical response time for
the complete system, the response speed will not be affected.
LIMIT SPEED:
Set the desired final limit speed.
KP/Tn :
Increase KP until the motor starts to oscillate (audible, and visible
on the oscilloscope) and then reduce KP again until the oscillations
have definitely stopped and stability is assured.
Use the motor-specific default value for Tn .
Start reversing mode :
Start the reversing mode (F8, v1/v2 approx. +/-10% of n
nom
for the motor).
Observe the speed response on the oscilloscope. If the settings are correct,
there must be a stable step response in both directions.
ò
ò
ò
ò
Diagram : Step response
n = speed
SW = setpoint
t = time
1 = optimum
2 = KP too high
ò
ò
ò
ò
KP :
You can produce a fine tuning of the speed response by cautiously increasing KP.
Aim: the smallest overshoot, but still retaining good damping.
A larger total moment of inertia make it possible to use a larger value for KP.
PID-T2 :
You can dampen out disturbances, such as a small amount of play in the gearing,
by increasing PID-T2 to about 1/3 the value of Tn.
FEEDBACK :
You can further improve the smooth runnning by using FEEDBACK, especially for
small drives with a low torque.
End reversing mode :
Finish the reversing mode operation (F9).
Set up the correct, motor-specific value for Ipeak (current controller) again. Start up reversing mode
again, and observe the step response. If there is any tendency to oscillation, reduce KP slightly.
Save the present parameter set in the EEPROM. Click on the button. - A.4.024.3/9
Quick Start 7
BECKHOFF
06.00 - A.4.024.3/9
Optimization