LSIS XBF-AD04A User Manual

Chapter 15 PID Function (Built-in function)
15 - 3
15.2 PID Control
15.2.1 Basic theory of PID control
Here describes basic theory of PID control and how to configure PID control.
(1) Terms
Terms used in this user manual are as follows.
▪ PV: status of plant detected by sensor (Process value)
▪ SV: Target value (Set Value) to control plant, if control is done normally, PV should follow the SV.
▪ E: error between SV and PV. It can be expressed as (SV-PV).
▪ Kp: proportional coefficient
▪ Ti: Integral time constant. Sometimes called integral time
▪ Td: Derivative time constant. Sometimes called derivative time
▪ MV: Control input or control device output. The input to plant to make PV follow the V
▪ Ts: Sampling time, a cycle of operation to execute PID control
(2)PID operation expression
Basic PID operation expressions are as follows.
PID control operation expressions of XGB series are more complicate than expression (15.2.1) ~
(15.2.5) mathematically but those are base on the above expression. The followings describe the
characteristics of control process with an example that controls the output temperature of heating
system in figure 15.1. At this example, the system and PID parameters imaginary to help the
comprehension and those may be different with real heating system. If the heating system in
figure 15.1 is expressed as second order system with transfer function like expression (15.2.6) in
frequency domain, it is expressed as differential equation like expression (15.2.6) in the time
domain.
That is, x(t) is Manipulated value and y(t) is Process value.
PVSVE 
EKMV
PP


 Edt
T
K
MV
i
P
i
dt
dE
TKMV
dPd

diP
MVMVMVMV 
))53)(12(
32
 ss
Transfer function =
(15.2.6)
)()(5
)(
32
13)(
32
6
2
2
txty
dt
tdy
dt
tyd

(15.2.7)
(15.2.1)
(15.2.2)
(15.2.3)
(15.2.4)
(15.2.5)

LSIS XBF-AD04A Specifications

General

Brand	LSIS
Model	XBF-AD04A
Category	Controller
Language	English