A Control Systems Laboratory Experiment on Transfer Function Emulation

This paper presents a low-cost experimenter kit for emulation of transfer function (TF) using a digital controller. The experimenter kit contains an on-board step input generator, an in-circuit-programmable digital controller and a simple OPAMP-based low-pass filter to present the final output of the synthesized transfer function. The use of this experimenter kit involves the knowledge of transfer-function-basics, elements of digital control, Z-transform and difference equation calculation principles. The set up is also accompanied by a template program for the digital controller, so as to enable the students to input the components of the TF-calculation easily, or use one's own program using C-language. Using this experimenter kit, the students can synthesize numerous transfer functions, within a range of pole-locations, and observe the output from the experimenter kit using standard digital storage oscilloscope (DSO). A brief description of the set-up is presented, along with the pedagogical approach used. A method to `approximate' the resulting difference equation is also presented. A few examples with results are presented to validate the usefulness of the set-up. The set-up encourages the student to follow the `do-it-yourself' approach and gives the student an idea about implementing TFs in real-time using digital controllers.