Introduction to Industrial Automation

6.7.3   Three Terms (PID) Control Modules

In every industrial production process, there is always a need for continuous control of a physical 

variable such as hydraulic pressure, temperature, the rotation speed of a motor, etc. Therefore, the 

PLC units should contain specific hardware to enable this. Most of the currently available PLCs 

in the market contain an embedded software program for applying analog control of three terms 

(PID control), which is stored in the memory of the PLC and is called from the user’s program 

3-

Discrete signals

from limit switches

Moving

carrier

Motion data

from CPU of PLC

Information

to CPU of PLC

Stepper

motor

module

3–6 control

loops per

module 

Power supply and driving

circuit of stepper motor

Position encoder