Modular Lumped Mass Experiment

A Lumped Mass Experiment is proposed for integration into multiple course curriculums. The design of the associated apparatus has taken into account the factors of cost, safety, ease of machining, modularity, reliability, mobility, size, reproducibility and aesthetics. The system incorporates adjustability for mass, spring constant(s) and damping coefficient for a large set of combinational effects. The software program “Working Model” was employed for the preliminary modeling of a set of practical systems. This paper discusses the equipment and fabrication requirements for the lumped mass apparatus. The experiment enables the students to fully examine the salient properties of flexible systems including natural frequencies, mode shapes, and characteristic transient and frequency responses. Students in a Vibrations, Controls, or a Mechatronics related exercise would be challenged to generate the mathematical models of the proposed modes of experimentation both in the Time and S-domains. The system can demonstrate the vibrational response characteristics of single, double and triple degree of freedom systems. The positions of each of the degrees of freedom are acquired using optical linear encoders and a National Instruments data acquisition board using a LabVIEW interface. The experiment uses the theoretical values that are calculated during the pre-laboratory section for comparison purposes. The uncertainty behind the measurement system is analyzed. Plots of input force vs. output amplitudes and phases are generated for the various operating frequencies of the system. These results are finally compared to the predicted results and conclusions are drawn. A sample laboratory handout is presented.