Moog DS2110, Инструкция по установке и эксплуатации

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CHAPTER 5.0 Functional Overview 5-41
CDS7324 (FORMERLY LSF-0819)
Rev. A INSTALLATION & USER’S MANUAL
The mode parameter determines the number of multiplications used to compute the filter output. If
velocity_loop_filter_mode is set to 1, then only parameters b0, b1, b2, a1, a2 are used to compute the filter
output. This configuration is consistent with a second order low-pass or high-pass butterworth digital filter.
If
velocity_loop_filter_mode is set to 2, then all 9 parameters are used to compute the filter output. This
configuration is consistent with a second order band-pass or band-stop butterworth digital filter.
Naturally, lower order filter designs are allowed. For example, a first order filter. But in this case the unused
parameter must be set to zero.
5.11.2.4.1 Low-pass filter
For example the coefficients of a second order low-pass butterworth filter with a cut-off frequency of 0.1 time’s
half the sampling frequency, can be determined as being: -
b
0
.. b
2
= 0.02008336556421 0.04016673112842 0.02008336556421
a
0
.. a
2
= 1.00000000000000 -1.56101807580072 0.64135153805756
If the velocity loop rate modulus is 4 and the switching frequency parameter is 9920Hz, Then, the velocity loop
sample rate is 400
μ
s approximately (= 2.5KHz approx).
Hence, the 0.1 filter factor means that the low-pass filter cut-off is 0.1*(Fs / 2) = 0.1*(2.5KHz / 2) = 125Hz.
Setting the filter coefficient parameters of the filter accordingly and setting the mode to 1, will implement this filter,
in the drive. Note that parameter a0 is always 1.0.
5.11.2.4.2 Band-stop filter (Notch)
The coefficients of a second order band-stop butterworth filter with a notch between 0.1 time’s half the sampling
frequency, and 0.2 time’s half the sampling frequency, can be determined as being: -
b
0
.. b
4
= 0.80059240346457 -2.88889936383274 4.20729857288451
-2.88889936383274 0.80059240346457
a
0
.. a
4
= 1.00000000000000 -3.21244081546948 4.16713184175608
-2.56535791219600 0.64135153805756
If the velocity loop rate modulus is 4 and the switching frequency parameter is 9920Hz, then, the velocity loop
sample rate is 400
μ
s approximately (= 2.5KHz approx).
Hence, the notch entry cut-off is: -
0.1*(Fs / 2) = 0.1*(2.5KHz / 2) = 125Hz.
And, the notch exit cut-off is: - 0.2*(Fs / 2) = 0.2*(2.5KHz / 2) = 250Hz.
Setting the filter coefficient parameters of the filter accordingly and setting the mode to 2, will implement this filter,
in the drive. Note that parameter a0 is always 1.0.