Reverse and Direct Action of a PID Controller

Snapshot of the front panel of the simulator:

• What is needed to run the the simulator? Read to get most recent information!
• Tips for using the simulator.
• The simulator: pid_reverse_direct.exe.

Description of the simulated system

In this simulator a level control system for a liquid tank is simulated. The control signal controls the mass outflow from the tank. The user can select the sign of the controller gain. The default PID parameter values (already set on the simulator) can be used.

Video

Here is an instructional video where the present simulator is used as an example: Reverse or direct action in the PID controller?

Aim

The aim of this simulator is to observe the consequences of selecting wrong sign of the controller gain.

Motivation

Commercial controller give the user the option to select the controller gain according to the process gain. Selecting wrong sign has dramatic concequences for the stability of the control loop.

Tasks

1. Explain (without simulating) that the left tank process has positive gain, and that right tank process has negative gain.
2. What happens to the stability of the control systems if you select the wrong mode among the reverse and direct modes?
3. What happens to the stability of the control systems if you select the correct mode(s)?

[SimView] [TechTeach]

Updated 15 August 2017. Developed by Finn Haugen. E-mail: finn@techteach.no.