# The Nyquist App for Android and iPhone

In our Nyquist App, you can analyze the stability of the closed loop by using the Nyquist stability criterion. With the Nyquist stability criterion, you can determine the stability of the closed loop based on the frequency response of the open loop, without explicitly calculating the poles of the closed loop.

The Nyquist App is available in your Android and Apple App Store, respectively.

We hope you enjoy using the app and we are of course highly appreciating any feedback.

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This app was delevoped at the Institute for Systems Theory and Automatic Control of the University of Stuttgart and accompanies the lecture "Einführung in die Regelungstechnik" at the University of Stuttgart. Nevertheless, the content and tasks are self-contained, and we encourage all interested in this topic to play with the app and practice the Nyquist stability criterion. For more information on the Nyquist App and its underlying concepts, we refer the reader to a paper with the title "Smartphone Apps for Learning Progress and Course Revision" that we submitted to IFAC World Congress 2020.

In this app, the user can practice the Nyquist stability criterion. With the Nyquist stability criterion, one can determine the stability of the closed loop based on the frequency response of the open loop without explicitely calculating the poles of the closed loop. Hereby, the user can choose between three different levels of difficulty. In each level, the frequency response of an open loop is plotted together with thenumber of poles in the open right half plane and the number of poles on the imaginary axis. The task is to determine the encirclements of the locus around the critical point (-1,0), and to conclude whether the closed loop is stable or unstable. As the frequency responses are randomly generated, this app offers an unlimited number of tasks for the user to exercise the Nyquist criterion.

0. Language Notice

Only the German version of the terms of use and privacy policy are legally binding, this English version is just an orientation for people that don't speak German.

1.1 Usage

1.2 Contact
The given contact address must not be used for abusive reasons, such as sending ads or any other spam.

1.3 Data Protection

2.1 Access Rights
To provide complete functionality the App needs no access rights.

2.2 Personal Data
In this chapter we describe how we collect and process your personal data. No personal data is collected and processed by us.

3. Update Notice

4. Impressum

Universität Stuttgart
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Institute for Systems Theory and Automatic Control
Pfaffenwaldring 9
70569 Stuttgart
Germany
Phone: ++49 (0)711 685-67734
Fax: ++49 (0)711 685-67735
E-Mail: sekist@ist.uni-stuttgart.de
Internet: www.ist.uni-stuttgart.de