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Installation, Operation, & Maintenance Manual
ES-09374-1
PID Control
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See the actions in graphical form in the picture below.
Figure 8-24 PID Control Chart
PID Tuning Methods
The positioner automatically adjusts the PID parameters in the calibration process, but
you can change the values for proportional gain (Kp), integral time (Tr) and derivative
time (Td) manually. To this end, there are a few methods for adjusting the parameters
(tuning).
Limit Sensitivity Method
This method will work on the closed loop setting. It will first reduce the effect of the
integral and derivative actions to a minimum. Only then will it start with the gain (Kp)
and increase it until the controlled variable oscillates with the amplitude that is constant
making small perturbations in the system.
The most common adjustment is the one that reaches a quarter of the previous
amplitude. This method can be used in many processes.
Reaction Curve Method
This method is widely used in first order systems since it is less complex. It will present
a S-shaped curve through the two constants delay (L) and time (T), through the
K-coordinate.
Attempted and Error Method
This is one of the most used methods because it is simple. It consists in modifying the
control actions and observing the effects on the process (as the name suggests).
However, to be able to work with this system, it is important to have knowledge of both
the process and its algorithm.
It cannot be used for open loops because it can generate instability when the gains are
too low or too high.
Another disadvantage that can occur with this method is that depending on the amount
of adjustment, it will take a lot of time to tune. Depending on the conditions, this could
impair the process.
Configuration
PID control uses proportional, integral, and derivative actions together.
As it joins all the control actions it makes the error correction faster and more
assertive by eliminating the offset left by the proportional and derivative
actions.
Configuration
August 23, 2022
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