pid.py 文件源码

def _filter_transfer_function(cls,
                                  frequencies, filter_values,
                                  frequency_correction=1.):
        """
        Transfer function of the inputfilter part of a pid module
        """
        frequencies = np.array(frequencies, dtype=np.complex)
        module_delay = 0
        tf = np.ones(len(frequencies), dtype=complex)
        # input filter modelisation
        if not isinstance(filter_values, list):
            filter_values = list([filter_values])
        for f in filter_values:
            if f == 0:
                continue
            elif f > 0:  # lowpass
                tf /= (1.0 + 1j * frequencies / f)
                module_delay += 2  # two cycles extra delay per lowpass
            elif f < 0:  # highpass
                tf /= (1.0 + 1j * f / frequencies)
                # plus is correct here since f already has a minus sign
                module_delay += 1  # one cycle extra delay per highpass
        delay = module_delay * 8e-9 / frequency_correction
        tf *= np.exp(-1j * delay * frequencies * 2 * np.pi)
        return tf