Chapter 7 Usage of Various Functions
7-
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7.1.5 PID control function
1) Introduction
This chapter will provide information about the built-in PID (Proportional Integral Differential) function of K7 Basic Unit.
The K7 series does not have separated PID module, and the PID function is
integrated into the Basic Unit.
The PID control means a control action in order to keep the object at a set value (SV). It compares the SV with a sensor
measured value (PV : Present Value) and when a difference between them (E : the deviation) is detected, the controller
output the manipulate value (MV) to the actuator to eliminate the difference. The PID control consists of three control
actions that are proportional (P), integral (I), and differential (D).
The characteristics of the PID function of K7 is as following;
- the PID function is integrated into the CPU module. Therefore, all PID control action can be performed with instruction
(PID8,PID8AT) without any separated PID module.
- Forward / reverse operations are available
- P operation, PI operation, PID operation and On/Off operation can be selected easily.
- The manual output (the user-defined forced output) is available.
- By proper parameter setting, it can keep stable operation regardless of external disturbance.
- The operation scan time (the interval that PID controller gets a sampling data from actuator) is changeable for
optimizing to the system characteristics.
<Figure 1-1> Block diagram of PID control system
PID
calculation
Set Value
Present Value
PV
SV
MV
Manipulation
value
Manual MV
D/A
converting
module
Control
object
Sensor
module
Automated MV
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