Omron C200HX Operation Manual page 288

Special Math Instructions
270
cording to the time that has passed. The strength of the integral operation is indi-
cated by the integral time, which is the time required for the integral operation
amount to reach the same level as the proportional operation amount with re-
spect to the step deviation, as shown in the following illustration. The shorter the
integral time, the stronger the correction by the integral operation will be. If the
integral time is too short, the correction will be too strong and will cause hunting
to occur.
Step response
Deviation
0
Operation
0
amount
Step response
Deviation
0
Operation
0
amount
Derivative Operation (D)
Proportional operation and integral operation both make corrections with re-
spect to the control results, so there is inevitably a response delay. Derivative
operation compensates for that drawback. In response to a sudden disturbance
it delivers a large operation amount and rapidly restores the original status. A
correction is executed with the operation amount made proportional to the in-
cline (derivative coefficient) caused by the deviation.
The strength of the derivative operation is indicated by the derivative time, which
is the time required for the derivative operation amount to reach the same level
as the proportional operation amount with respect to the step deviation, as
shown in the following illustration. The longer the derivative time, the stronger
the correction by the derivative operation will be.
Step response
Deviation 0
Operation
0
amount
Ramp response
Deviation 0
Operation
0
amount
Integral Operation
PI Operation and Integral Time
Ti: Integral time
Derivative Operation
PD Operation and Derivative Time
Td: Derivative time
Section 5-21
PI operation
I operation
P operation
PD operation
P operation
D operation