CNC Setup Utility Manual
P/N 70000490C - Tuning the Current, Velocity, and Position Controller
5-4
All rights reserved. Subject to change without notice.
10-December-04
Table 5-2, Spindle Motors
Motor MC_2920:
MC_2921:
SM 055A
15,000 to 20,000
45,000 to 60,000
SM 075A
10,000
50,000 to 70,000
SM 100A
10,000
30,000 to 45,000
SM 120A
25,000
50,000
SM 055C/D
15,000
40,000
SM 075C/D
10,000
40,000
SM 100C/D
5,000
35,000
Frequency Auto-tuning Test
The system provides a frequency auto-tuning feature for the velocity
controller.
To auto-tune using the frequency test
1. On the Software Options menu, select
Motion Setup/Testing
(option 3) and press
ENTER
.
2. Press
TuneMod
(
F6
). Select
Automatic
and press
ENTER
.
3. On the MST screen, select an axis [
X
,
Y
,
Z
,
U
, or
S
(spindle)]. This
activates the axis.
4. Press
Tuning
(
F7
) to display a pop-up menu with the tuning mode
tests. Select
Frequency Tune
and press
ENTER
.
NOTE:
Frequency tune should be done before Velocity tune.
Frequency tune will calculate the oscillating frequency of the axis and
set the following Machine Constants:
MC_2
x
18:
x
Velocity Filter (FIR filter)
MC_2
x
35:
x
Torque Notch Filter Freq. (.1 Hz)
MC_2
x
36:
x
Torque Notch Filter Damp. (.1 dB)
The velocity proportional gain is increased by 200 per iteration. A step of
800 mm/min is sent to the velocity controller. After gathering 128
samples (step response), an inverted step is sent again to return motor to
its initial position. The frequency spectrum of the step response is
calculated through a Fast Fourier Transform (FFT). Then, the power
spectral density (PSD) is calculated from the FFT. The total signal
energy is calculated from the PSD and also the energy content in the
frequency band from 180 Hz. to 540 Hz. (system is expected to resonate
within this band). The energy percentage of this band with respect to the
total energy is calculated, and if the percentage is more than 50%
(system near point of oscillation), this phase is stopped and depending on
the oscillation frequency, some filters are activated.
If the oscillating frequency is between 100 and 600 Hz., the notch filter
frequency is set to the oscillating one, the damping to 6 dB and the FIR
filter is set to 1.
