Bilinear Transformation

Question

Hi,

This particular topic pertains to Digital Controls. I have a transfer function of my plant, which in this case is a servo motor, and it is in the z-domain. In order to determine the phase margin I need to look at the Bode plot, but first I have to use the bilinear transformation:

z = (1+(T/2)*w) / (1-(T/2)*w); T-sampling rate,
w = e^(j*omega) (frequency response)

Does MATLAB have a function that would do this transformation for me? To go from z-domain to w-domain.

Answer 1

There's a function called BILINEAR in the Signal Processing Toolbox, if you have it. I'm not sure if this is exactly what you need, but it's probably a good place to start.

EDIT: Some other options to check out that may help you: the functions C2D and D2C in the Control System Toolbox help to do conversions between continuous-time and discrete-time models.