Delta DVP-15MC Series - Page 404

Chapter 8 Logic Instructions
8-317
8_
PID Block Diagram (Dependent)
SV
PV
+
-
+
PID-P
Kc_Kp
REVERSE
X(-1)
PID_DIR
0
1
E
DEAD BAND
ERR_DBW
PID-I
Ti_Ki
Kc_Kp
>0
<=0
0
Ti_Ki
>0
<=0
0
PID-D
Td_Kd, Tf
0
>0
<=0
Td_Kd
BIAS
PID_MAN
+
+
+
MV
MV_LIMIT
MV_MAX, MV_MIN
MOUT_AUTO
MOUT
MOUT
PID_MAN
MOUT
0
1
0
1
0
1
 Precaution and Suggestion:
Owing to the fact that the instruction PID can be used in a lot of controlled environments, users have
to choose the control function appropriately. For example, to prevent the improper control from
occurring, PID_MODE can not be used in the motor controlled environment because it is set to 1 and
MV value is switched between MAX and MIN.
When users tune the parameters Kc_Kp, Ti_Ki, and Td_Kd (PID_MODE is set to 0), they have to
tune Kc_Kp first (according to the experience), and then set the Ti_Ki and the Td_Kd to 0. When
users can handle the control, they can increase Ti_Ki and the Td_Kd. When the Kc_Kp is 1, it
means that the proportional gain is 100%. That is, the error value is increased by a factor of one.
When the proportional gain is less than 100%, the error value is decreased. When the proportional
gain is larger than 100%, the error value is increased.
To prevent the parameters which have been tuned automatically from disappearing after a power cut,
we suggest users should store the parameters in the latched variables when PID_MODE =1 is
selected. The parameters which have been tuned automatically are not necessarily suitable for every
controlled environment. Therefore, users can modify the parameters which have been tuned
automatically. However, it is suggested that users only modify the Ti_Ki and the Td_Kd.
The instruction should be used with many parameters. To prevent the improper control from occurring,
please do not set the parameters randomly.
 The steps of tuning the parameters used with the instruction PID
Suppose that the transfer function of G（s）the plant is the first-order function
( )
a+s
b
=sG
, the SV is
1, the sampling time CYCLE is 10 milliseconds. It is suggested that the steps of tuning the parameters
are as follows.