Torsional Vibration Measurement Validated with Dynamic Modeling on a Grinder Rotor Assembly

This work presents a technique for measuring torsional vibrations and validates its application. The objective was to develop and validate a methodology and the necessary tools for investigating torsional vibratory dynamics in rotor assemblies. A bench grinder's rotor assembly and casing were modified to install a high-precision, high-speed incremental rotary encoder. The encoder's output signals were processed by a custom-designed data acquisition card, which recorded the timings of ۱۰۲۴ pulses per revolution. This card was equipped with a microcontroller and timer modules for this purpose. The pulse timings were analyzed to derive the Instantaneous Angular Speed (IAS), representing the velocities of torsional oscillations. Several tests were conducted, and the measured signals were transformed into the frequency domain to identify the Torsional Natural Frequencies (TNFs). A ۳-degree-of-freedom (۳DOF) dynamic model of the rotor assembly was then used to provide analytical estimates of the first two TNFs. Discrepancies of approximately ۲۲% and ۳۹% were observed between the measured and modeled TNFs, which were considered acceptable given the context of the model. These results are understandable, as the dynamic modeling relied on rough estimations for the grinding disks' material properties, the squirrel cage's geometry and material, and nominal values for the steel rotor material. In conclusion, the developed setup is capable of effectively studying torsional dynamics. Future work will focus on refining the dynamic model to minimize the discrepancies with experimental results.

کلیدواژه ها:

Instantaneous angular speed ، Torsional vibration ، Rotary encoder ، Rotordynamics