PRBS Example

Suppose that it is desired to design a controller for the current loop using data-driven methods instead of a model. The PRBS method can be used to obtain the frequency response of the open-loop system for this purpose. For the current loop, we will need the frequency response from V_REF to I_MEAS. Let us assume that the aquisition has been captured with Powerspy and stored in a dataframe.

>>> device = 'RFNA.866.01.ETH2'
>>> df_i_time
                t_global    I_MEAS_(A)                   V_REF_(V)           V_MEAS_(V)
                -       t_local        sample       t_local sample       t_local sample
0       1.597840e+09  1.597840e+09 -5.520654e-36  1.597840e+09    0.0  1.597840e+09    0.0
1       1.597840e+09  1.597840e+09 -5.520654e-36  1.597840e+09    0.0  1.597840e+09    0.0
2       1.597840e+09  1.597840e+09 -5.520654e-36  1.597840e+09    0.0  1.597840e+09    0.0
3       1.597840e+09  1.597840e+09 -5.520654e-36  1.597840e+09    0.0  1.597840e+09    0.0
4       1.597840e+09  1.597840e+09 -5.520654e-36  1.597840e+09    0.0  1.597840e+09    0.0
...              ...           ...           ...           ...    ...           ...    ...

Fig. 7 PRBS aquisition with V_REF (green) and I_MEAS (red).

With this data, the frequency response can easily be obtained by calling the following functions:

>>> import pyfresco.frm as frm
>>> fgc_frm = frm.from_fgc(device) # Get the FGC properties needed for the measurement
>>> F = frm.Frm_methods(fgc_frm, 'V') # Instantiate the class with the FGC properties
>>> df_freq = F.prbs(df_i_time, 'V_REF_(V)', 'I_MEAS_(A)')
>>> df_freq

            f        gain       phase
0       1.220852   16.797757  -20.015512
1       2.441704   15.510021  -36.172323
2       3.662556   13.963785  -47.810938
3       4.883409   12.442825  -56.015474
4       6.104261   11.044407  -61.922417
..           ...         ...         ...