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3. Instruction Set
3-249
Example 2: Block diagram of application on AC motor drive (S
3
+4 = 0)
PID
S+MV
Speed instruction (S)
Acceleration/deceleration
instruction (SV)
Acceleration/deceleration
output (MV)
Actual acceleration/
deceleration speed
(PV = S - P)
AC motor
drive
Speed
detection
device (P)
Example 3: Block diagram of application on temperature control (S
3
+4 = 1)
PID
Temperature instruction (SV)
Heating (MV)
Actual temperature
(PV)
Heater
Temperature
detection
device
Example 4: PID parameters adjustment
Assume that the transfer function of the controlled device G(S) in a control system is a first-order
function
()
a
s
b
sG
+
=
(model of general motors), SV = 1, and sampling time (T
S
) = 10ms. Suggested
steps for adjusting the parameters are as follows:
Step1:
Set K
I
and K
D
as 0, and K
P
as 5, 10, 20, 40. Record the SV and PV respectively and the results are
as the figure below.
1.5
1
0.5
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
K =40
P
K =20
P
K =10
P
SV=1
K =5
P
Time (sec)