10.4 FREQUENCY RESPONSE FUNCTIONS
- In many cases the behavior of a system must be determined experiementally.
- One common method is to excite the system with a range of input frequencies, measure the output response, and plot the gain and phase. This is the experimental equivalent of the Bode plot, called the Frequency Response Functions (FRF).
- Given a FRF, a transfer function can be developed by reversing the straight line method for drawing Bode plots.
- Consider the example below
- This can be converted by doing a straight line fit to the function. Because the graph is drawn using experimental values there is some need to allow for points that are off the straight line. In other words, fit the curve using a good educated guess.
