The first order lag element (PT1) is a common element of the measurement and control technology. It can be used for the damping of an input signal, like demonstrated in this example.
Beside the input signal, the constant “T”, which adjusts how quickly the output value reaches the input value after a time step, is a necessary input value. The bigger the value of T, the longer it will take.
In this example, the controller input signal for the valve position of a circuit is filtered by a first order lag element (PT1).
This element is modeled by using KULIs default calculation controllers and controlling elements. For a good overview, they are grouped in the subsystem “PT1 – Element”.
The time-discrete formula is included in the 1st calculation controller. Necessary inputs are the simulation time step, the current input value and the output signal of the former time step.
Additionally the constant T is used to adjust how quickly the output value reaches the input value after a time step.
The PID controller outside the subsystem is used to set the limits (in this example the valve opening / closing position is limited between 5 und 95 percent).Usable from release: KULI 9.1-0.01