Estimation of Closed-loop Performance

The purpose in this page is the follows:

Confirm the closed-loop system stability by Nyquist plot
Compare the open- and closed-loop system performance by calculating gain characteristic from w to z.

Type the following command on Matlab:

>> compare_perf

Example:

>> compare_perf
nominal transfer function for Gyu: stable
controller: stable
closed-loop system: stable

Nyquist plot of loop transfer function

gain characteristic from w to z

In the above example, the followings are confirmed firstly by checking the corresponding eigen values:

The nominal transfer function from u to y is stable.
The controller is stable.
The closed-loop system is stable.

The closed-loop system stability is also confirmed by the Nyquist plot.
Finally, the final figure shows that the closed-loop system performance is improved in the frequency range from about 30Hz to 500Hz.

Yasuhide Kobayashi

Last modified: Thu Jun 17 12:32:06 JST 2004