Process Control: Modeling, Design, and Simulation

M4.5. Step and Impulse Responses

Step responses of LTI objects can be determined or compared in a number of different ways. The following command compares the step responses of the continuous and discrete-time van de Vusse models previously entered in the MATLAB command window.

» step(vdv_tfc,vdv_tfd)

The resulting response is shown in Figure M4-1. Notice that a zero-order hold has been applied to the discrete step response. Also, note that the step command assumes that the time unit is seconds, which is not normally the case for chemical process systems.

Figure M4-1. Step responses of continuous and discrete van de Vusse reactor model. Illustration of zero-order hold. Notice the default labeling of a time unit of seconds.

Alternatively, the ...