Ny-Series Instructions Reference Manual (W560 - Omron NY532-5400 Reference Manual

2 Instruction Descriptions
The total of the manipulated variables for the proportional, integral, and derivative actions is the
manipulated variable for PID control. The changes in the manipulated variable for PID control for a
stepwise and ramp deviations are shown below.
Deviation
Stepwise response
0
Manipulated
variable
0
Derivative action only
2-PID Control with Set Point Filter
There are three main parameters that you must adjust to perform PID control: the proportional band,
integration time, and derivative time. These are called the PID constants. The values of the PID con-
stants affect the following two performances of PID control.
• Set point response: The ability to follow changes in the set point.
• Disturbance response: The ability of correcting the process value for large changes that are caused
by disturbances
A block diagram for basic PID control is shown below. The set point and disturbance enter the block
diagram at different positions. Therefore, finding the optimum PID constants for both set point response
performance and disturbance response performance is difficult. In other words, if the PID constants are
set for set point response, response to disturbances is slow. If the PID constants are set for disturbance
response, overshooting occurs.
Deviation
+
Set point
−
To enable both set point response and disturbance response, 2-PID control is used. The 2 in "2-PID"
indicates that there are separate parameters to adjust the set point response and the disturbance
response. A block diagram for this is shown below. A set point filter that includes an adjustment param-
eter is added. The PID constants are adjusted to maximize disturbance response. A set point filter
adjusts the set point to optimize the set value response for those values. You can adjust the values of
the PID constants and the set value of the set point filter independently to increase both the set point
response and the disturbance response.
Adjustment for set point response
Set point filter
Set point
2-674
Deviation
Time
Manipulated
variable
PID control
Integral action only
Proportional action only
Time
Disturbance
Manipulated
+
variable
+ Controlled
P+I
system
−
+
D
Adjustment for disturbance response
Manipulated
Deviation
variable
+ +
P+I
− −
D
Ramp response
0
0
Proportional action only
Process value
Disturbance
+
Process value
Controlled
system
+

NY-series Instructions Reference Manual (W560)

Time
PID control
Integral action only
Derivative action only
Time