Automating Manufacturing Systems - Process Control and ...

plc software - 32.8
orifice plate
magnetic
control valve
(pneumatic activated)
rotameter
venturi or nozzle
Figure 32.4
Sensor and Actuator Symbols and Types
32.4 PROGRAMMING FOR LARGE SYSTEMS
Previous chapters have explored design techniques to solve large problems using
techniques such as state diagrams and SFCs. Large systems may contain hundreds of those
types of problems. This section will attempt to lay a philosophical approach that will help
you approach these designs. The most important concepts are clarity and simplicity.
32.4.1 Developing a Program Structure
Understanding the process will simplify the controller design. When the system is
only partially understood, or vaguely defined the development process becomes iterative.
Programs will be developed, and modified until they are acceptable. When information
and events are clearly understood the program design will become obvious. Questions that
can help clarify the system include;
"What are the inputs?"
"What are the outputs?"
"What are the sequences of inputs and outputs?"
"Can a diagram of the system operation be drawn?"