PendCon

    







   Level Control for a

    Freely Configurable

    System  of Tanks

    and Pumps

















To keep the level of a fluid on a desired value is a standard task of process control. PendCon offers a level control experiment for a system consisting of up to three tanks. The outlet flow can be generated by a valve or a pump. By this way, several configurations with a varying degree of complexity of the system are possible.

The device for the outlet flow determines the type of the system: With the outlet valve, the type is zero whereas the type is one if a pump is used to generate the outlet flow. The pipe between the tanks can be closed or opened to get a one-, two-, or three tank system. By this way, six essentially different plants are possible. Each pump is actuated by a pwm-amplifier which is part of the experiment. The level is measured by an ultrasonic sensor.

As controllers, both, the PendCon Analogue Controller and the PendCon Digital Controller are possible. With the analogue controller, the handling of the experiment is more intuitive whereas with the digital controller, it is more flexible. The main educational goal of this experiment is to introduce the students into the basic topics and ideas of control system design such as

• Step and frequency response
• Linearization
• Tracking
• Disturbance rejection
• PID control
• Controller design based on the Nyquist criterion.

If only one or two tanks are used, controller design can be done by using simple formulas.










      Set-up of the experiment

      with only one tank, power amplifier,

      and digital controller














In the simplest case, the plant is driven as one-tank-system. With an outlet pump, it is linear and of type 1 whereas with an outlet valve, it is nonlinear and of type 0. In both cases, the controllers can be designed by simple closed formulas or by a little bit of trial and error. In this basic configuration, the emphasis is not so much on sophisticated controller design but more on understanding the basic concepts. By adding further tanks, it is possible to proceed step by step to more complicated topics.