Lecture 5: Higher-Order Open-Loop Systems

Three classes of higher-order systems are most often encountered:

• N first-order processes in series (multicapacity processes)

• Processes with dead time

• Processes with inverse response

Conclusions from N noninteracting capacities in series:

a. The response has the characteristics of an overdamped system; that is, it is S-shaped and sluggish.

b. Increasing the number of capacities in series increases the sluggishness of the response.

Conclusion from N interacting capacities in series:

• Interaction increases the sluggishness of the overall response.

We notice that initially the response is in the opposite direction to where it eventually ends up. Such behavior is called __________________________ and it is exhibited by a small number of processing units.

inverse response or nonminimum phase response

In all cases we notice that when the System possesses an inverse response, its transfer function has a ______________

positive zero.