Delta AH500 Programming Manual page 344

AH 5 00 Pr ogr am m ing Ma n ua l
a) The PID algorithm includes the forward action and the reverse action. Whether the action
is the forward one or the reverse one depends on the setting of PID_DIR.
The PID algorithm is as follows.
( )
=
MV K E t
P
E(t)S represents the derivative value of E(t), and
( )
.
E t
Action direction
Forward action
Reverse action

Control diagram: S represents the derivative action, and is defined as (Current
E(t)-previous E(t))/Sampling time. 1/S represents the integral action, and is defined as
(Previous integral value+Error value)×Sampling time. G(S) represents the plant.
T he instruction PID is inside the dotted line.
+

The symbols:
: Output value
MV
( )
: Error value
E t
Forward action
Reverse action
: Proportional gain
K
P
PV : Process value
SV : Target value
K : Derivative gain
D
K : Integral gain
I
Suggestion:
1. 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 when it is set to 1.
2. When users tune the parameters K
tune the K first (according to the experience), and then set set the K
P
users can handle the control, they can increase the K
four below. When the K
value is increased by a factor of one. When the proportional gain is less than 100%, the error
value is decreased. When th proportional gain is larger than 100%, the error value is
increased.
6 - 1 7 6
t
dE ) ( t
∫
+ +
K E ) ( t dt K *
I D
dt
0
( )
=
E t PV
( )
=
E t SV
1/K
1/S
-
K
S
( )
= −
E t PV
( )
= −
E t SV
, K , and K
P I
is 100, it means that the proportional gain is 100%. That is, the error
P
1
( )
represents the integral value of
E t
S
PID algorithm
( ) ( )
t - SV t
( ) ( )
t - PV t
I
+
+
1/K
P
+
D
SV
PV
(PID_MODE is set to 0 or 2), they have to
D
and the K , as illustrated in example
I D
G(s)
and the K to 0. When
I D