.IndustrialControlSystems.Controllers.Examples.TestPID_tracking

Information

Description

In this example have been tested the tracking mode of the proportional + integral + derivative controller.
The process to be controlled has the following transfer function

   Y(s)          (1+15s)
   ----  =  ----------------
   U(s)       (1+10s)(1+2s)

There are two processes:

with a PID controller,
and a PID controller with tracking mode

The output signal of the process controlled without tracking is the red line, while the green line is the output of the process controlled with the tracking mode.

The CS of the controller becomes equal to the track reference signal TR when the Track Switch signal becomes true.

Bumpless transition

If the Track Reference signal moves the Process Variable at the Set Point reference value, once the Tracking mode is disabled there should be a bumpless transition. The images below show a bumpless transition.

The integrative effect, represented by the integrator in the feedback path of the PID controller (see the PID block diagram here), is forced to follow the tracking reference (Iaction signal in the last figure). In the same figure there is a small variation of the CS when the automatic mode start again, because the PV is not exactly at the SP value and thus the proportional action introduce a little displacement (the blue line at t = 100).

Discrete time

If the model parameter Ts is >=0 the continuous time controllers are replaced by their discrete time versions.
The effect of various discretisation method can be studied.

examples

Ts = 0.01 s and method = BE

Ts = 0.05 s and method = BE

Revisions

Industrial Control Systems (v 1.0.0) : April-May 2012