Getting Started

Chapter 3
Analyzing Models

This chapter shows how you can analyze models using tools provided by the Control System Toolbox. It begins by introducing the LTI Viewer, a graphical user interface (GUI) that simplifies the analysis of linear, time-invariant systems.

The chapter continues with a discussion of commands provided by the Control System Toolbox for plotting the time and frequency responses of linear models. This set of commands provides an open and extensible environment for the analysis of control systems. You can use these commands when you need more flexibility than the LTI Viewer provides.

Finally, this chapter discusses the Simulink LTI Viewer, for use with Simulink. You can use this tool to linearize models or parts of models, analyze linearized models, and compare linear and nonlinear models.

The LTI Viewer is a GUI for viewing and manipulating the response plots of linear models. You can display the following plot types for linear models using the LTI Viewer:

• Step and impulse responses
• Bode and Nyquist plots
• Nichols plots
• Singular values of the frequency response
• Pole/zero plots
• Response to a general input signal
• Unforced response starting from given initial states (only for state-space models)

Note that time responses and pole/zero plots are available only for transfer function, state-space, and zero/pole/gain models.

Note    The LTI Viewer displays up to six different plot types simultaneously. You can also analyze the response plots of several linear models at once. However, all models must have the same input and output sizes. If your models have unequal input or output sizes, you must display them in different LTI Viewers.

Model Order Reduction

LTI Viewer