Chapter 6 Usage of Various Functions
6-6
6.1.4 PID Control Function
1) Introduction
This chapter will provide information about the built-in PID (Proportional Integral
Derivative) function of PLC option card of iS7 inverter series. 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 derivative (D).
The characteristics of the PID function of PLC option card for iS7 inverter is as following;
• The PID function is integrated into the CPU module.
• P operation, PI operation, PID operation and On/Off operation can be selected easily.
• PWM(Pulse Width Modulation) output is available.
• The manual output (the user-defined forced output) is available.
• By setting proper parameter, 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.
• SV Ramp and Delta MV function are available.
P I D
calculation
Set Value
Present Value
PV
SV
MV
Manipulation
value
Manual MV
D/A
converting
module
Control
object
Sensor
A/D
converting
Automated MV
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