<p>Learning by doing has proven to have numerous advantages over traditionally taught courses in which the instructor teaches the topic while students remain passive learners with little engagement. Dynamics is one of the main branches of mechanical engineering. It encompasses traditional dynamics, mechanical vibrations, and introduction to control theory which primarily focuses on the derivation of mathematical models of vibratory mechanisms, systems, and machines to analyze their response to any given input. The vast majority of mechanical engineering undergraduate students struggle to represent machines/mechanisms with an equivalent mass-spring-damper model, derive the equations of motion, and link the theory to real-world applications. Students' deep conceptual understanding and higher-order skills in these courses can be enhanced when traditional lectures are infused with demonstrations of the fundamental topic using portable laboratory equipment. This impact of these demonstrations can be further enhanced when the students themselves can operate and manipulate the mechanisms. Observing the impact on system behavior when directly changing different system variables provides the opportunity for application and analysis of the concepts being studied.</p><p>In this study, we developed three novel, open-source, and low-cost portable vibratory equipment mechanisms to be utilized in mechanical vibrations and control theory courses along with their associated laboratories. These advantages provide the potential for every student to individually operate and observe each mechanism's behavior. The first mechanism consists of a cantilever beam, support, and multiple springs. It demonstrates the fundamentals of free vibrations, illustrates the quantities used to find the lumped mass-spring-damper model, and can be used to validate theory through experimental data collected from ADXL accelerometers, Arduino, and Matlab. The beam is designed to enable multiple spring attachments at different locations between the support and the beam. Additional masses can also be attached to the beam to change the effective mass. All parts of the mechanism including the helical springs are 3D printed in polylactic acid (PLA). The second mechanism is a 3D printed pendulum, comprised of a mount for an encoder, a pendulum rod, and magnets to change the tip load. The mechanism can be used to study system identification aligned to theory and free-response motion data from the encoder and Matlab. The third mechanism is a rectilinear motion bench incorporating a rail, two sliders, dc motor, springs, two ADXL accelerometers, connecting rod, and scotch yoke mechanism. While the main parts of the mechanism are 3D printed in PLA, horizontal springs are 3D printed in thermoplastic polyethylene (TPU) to accommodate required the compression and tension loads during motion. The total mass of the carts can be changed by adding loads on each cart. Additionally, springs possessing various stiffnesses are designed to modify the properties of the system. The rectilinear system can be used to study free and forced vibrations, system identification, and trajectory control by designing a PID controller. The superiorities of the proposed mechanisms over educational turn-key equipment are their low-cost, their lightweight portability, and their open-source design. Any of the parts can be 3D printed for a replacement if broken or damaged due to overuse.</p>

3D-Printed Laboratory Equipment for Vibrations and Control Theory Courses: Pendulum, Cantilever Beam, and Rectilinear System

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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