Experimentally Identifying the Transfer Function of an Electromechanical System

An experiment is developed in which the instructor demonstrates the acquisition of frequency response data for an electromechanical system (an X-Y recorder). Students are given copies of the acquired data, from which they create an amplitude response plot and develop a transfer function for the system. Using a simple optimization routine, students tweak the model until the predicted amplitude response most closely matches the experimental data. The model is refined further by adding a zero to the transfer function. Students compare the predictions of their models to the experimental data and answer related questions on a lab worksheet, all within one three-hour lab period. In this paper, the apparatus, demonstration, data reduction, system identification, and results are described. A videotaped demonstration of the experiment, sample data, and the lab handout and worksheet are available online at www.rose-hulman.edu/ES205/labs.html. In future work, the experiment will be modified to measure phase response.