This page is dedicated to ACT (Automatic Control Toolbox) for Ti-89. This program, written by me, will be a great helping tool  to you if you're interested, for study or job, in the process control analysis and syntesis, both in numeric or analogic technology. There are some great programs to analyze closed loop system properties from the open loop transfer function . Thanks to the most powerful program included in ACT you'll plot Nichols diagrams and, with the Nichols maps, you'll can study the closed loop properties, as you can see in this figure:

Then what you're waiting for, download now the ACT and let me know what do you thing about it!!!