Ch05 ControlSys-4e-A&S 03-21, 03-22-2013

Chapter 5
INDUSTRIAL CONTROL SYSTEMS
REVIEW QUESTIONS
5.1

What is industrial control?
Answer: As defined in the text, industrial control is the automatic regulation of unit operations and their associated equipment as well as the integration and coordination of the unit operations in the larger production system.

5.2

What is the difference between a continuous variable and a discrete variable?
Answer: A continuous variable is one that is uninterrupted as time proceeds, and it is generally considered to be analog, which means it can take on any value within a certain range. A discrete variable is one that can take on only certain values within a given range, such as on or off.

5.3

Name and briefly define each of the three types of discrete variables.
Answer: The three types of discrete variables are (1) binary, (2) discrete other than binary, and (3) pulse data. Binary means the variable can take on either of two possible values, ON or OFF, open or closed, and so on. Discrete variables other than binary are variables that can take on more than two possible values but less than an infinite number. Pulse data consist of a series of pulses and each pulse can be counted.

5.4

What is the difference between a continuous control system and a discrete control system?
Answer: A continuous control system is one in which the variables and parameters are continuous and analog. A discrete control system is one in which the variables and parameters are discrete, mostly binary discrete.

5.5

What is feedforward control?
Answer: Feedforward control is a means of control that anticipates the effect of disturbances that will upset the process by sensing them and compensating for them before they affect the process. The feedforward control elements sense the presence of a disturbance and take