Rockwell Automation 1746-BTM Barrel Temperature Control Module User Manual - Manual (Page 44)

Publication 1746-UM010B-EN-P - April 2001
4-4 Setting Autotune and Gains Values
If the loop is slow in reaching the set point either at start–up or at a
change of set point, (See Figure 4.2) you may be able to improve the
loop response by doing one or more of the following (in order of
effectiveness):
1. increase the proportional gain
2. increase the integral gain
3. decrease the derivative gain
Figure 4.2 Loop Slow to Set Point
Using the PID Equation The module provides dependant PID control action. Dependent
control action can be represented by the equation
The module is capable of performing PID control by calculating the
solution to an approximation of the PID equation. The approximation
is represented by the equation:
Set Point
CV K
p
E K
i
E D
t
K
z
E d
t d
------ +
⋅
0
t
∫
+
 
 
 
 
=
Where:
CV = Control variable
K
p
= Proportional gain (no units)
E = Error (SP-PV or PV-SP)
K
i
= Integral gain (repeats/seconds)
K
z
= Derivative gain (seconds)
t = Time
CV K
p
E K
i
E
∆
t
K
z
∆
E
∆
t
------- +
⋅
0
t
∑
+
 
 
 
 
=
E
0
t
∑ ∆
t
⋅
E
1
∆
t E
2
∆
t E
3
∆
t etc +
⋅
+
⋅
+
⋅
=
Where:
.....