ERI: System Tautochronic Pendulum Vibration Absorbers for Next-Generation Propulsion Systems and Other Machinery

Oakland University, Rochester MI

Investigators

Abstract

This Engineering Research Initiation (ERI) award supports research that enables the development of unique vibration and noise control technologies to reduce vibrations in rotating systems, including helicopter rotors and crankshafts of internal combustion engines widely used in fuel-efficient conventional and hybrid electric vehicles powertrains, thereby promoting the progress of science, advancing prosperity and welfare, and securing the national defense. The research will generate new fundamental knowledge related to the design of centrifugal pendulum vibration absorbers (CPVAs) for the next-generation of electrified machinery that has the potential to improve both propulsion efficiency and driver experience for hybrid electric and electric vehicles. CPVAs consist of pendulums mounted on a rotor, driven by system rotation, and when properly tuned, can efficiently smooth problematic vibration-inducing torsional surging during operation. Current state-of-the-art overtuning approaches of a CPVA and rotor system will result in reduced vibration correction performance for a given absorber mass. This project will solve this challenge via a novel tautochronic tuning approach, which has the potential to enable more direct tuning without stability concerns, thereby reducing added driveline inertia required to achieve performance objectives. This award will also support community outreach and student research projects involving industry collaborations and the development of new curriculum in electrified propulsion engineering and training of the next generation STEM workforce. This research aims to make fundamental contributions to a system tautochrone tuning methodology, which consists of a path for the absorber mass to follow that accounts for the inertial coupling of the absorber to the base (rotor), and results in a constant period free vibration of the system that is independent of amplitude. This tuning methodology and its enhancements to vibration absorber design has been identified in a gravity field, but a number of important scientific questions and challenges remain for the centrifugal field. Similar to the gravity field, conditions for the tautochronic tuning in a centrifugal field will be obtained from a general period function for this oscillator that is derived by transforming the differential equation to a standard form, and then requiring that the polar angular speed is independent of the polar radial coordinate. The tautochronic tuning conditions will generally consist of a nonlinear differential equation for the radius of curvature of the absorber path, whose solution is the system tautochronic motion path. A fundamental difference in the centrifugal field is that the oscillator coefficients depend on the system momentum constant. Consisting of both absorber and rotor motion, this generalization to system momentum could revolutionize the concept of order-tuning, where a system tautochronic path is expected to remain tuned across all momentum levels, instead of just rotor speeds, as has been understood for many decades. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.