10 PID CONTROL INSTRUCTIONS
10.1 Overview
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10 PID CONTROL INSTRUCTIONS
There are two types of instructions for PID control.
• PID OPERATION INSTRUCTIONS
• PID CONTROL INSTRUCTIONS
For how to use or compare them, refer to the following.
Page 1134 PID operation instruction and PID control instruction
10.1 Overview
This section describes the operation methods, procedures, and helpful functions of PID control by using PID control
instructions.
The PID control instructions include those for inexact differential and exact differential.
Inexact differential is PID control that applies a primary delay filter to the input of a differentiation term, and is
useful for the following.
• For control susceptible to high-frequency noise
• When energy effective to actuate an operation end is not provided when a step change occurs in an exact
differential system
Exact differential is PID control that uses the input of a differential term as it is.
Operation method
Two types of operation methods are available for PID control by using PID control instructions: velocity type and process
value differentiation type.
The following table summarizes each operation methods.
Operation method Description
Velocity type This type of control calculates variations in the manipulated values (MV) during PID operation. The actual MV is the
accumulated value of variations calculated each sampling period.
Process value differentiation
type
This type of control performs PID operation by differentiating the process value (PV). Since the deviation is not subject to
differentiation, an abrupt change in output due to derivative action can be reduced when the deviation is generated by
changing the set value.
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