Abstract

Rotating machinery systems experience torsional vibrations with varying frequencies to some degree during normal operation. These vibrations if not controlled properly may cause severe system performance limitation and reduction of the fatigue life. Attenuation of torsional vibrations in these systems is a challenging engineering problem and raises several important issues in industrial applications.
The present research aims at developing a novel hybrid torsional vibration damper incorporating a conventional Centrifugal Pendulum Vibration Absorber (CPVA) with the Magnetorheological (MR) damper capable of suppressing torsional vibrations at different excitation frequencies. In fact, CPVA and torsional MR damper have been investigated separately in previous research, however, there has been no study reported on integrating the two systems for the attenuation of torsional vibration.
In this research study, first, the governing equations of motion for both horizontal and vertical CPVA have been derived using Lagrange’s principle to investigate the effect of gravity on the dynamics and performance of CPVA. Moreover, softening nonlinear behavior of the pendulum absorber and its effect on the natural frequency of the system has been investigated.
Next, a rotary MR damper prototype was optimally designed, manufactured and tested. The design process of the rotary MR damper included several critical factors, particularly, analysis and design of the magnetic circuit of the MR damper. In order to ensure efficient design of the proposed damper, a finite element (FE) model of the rotary MR damper was developed to accurately evaluate the magnetic field distribution in the MR fluid and electromagnet core generated by the built-in electromagnet. The developed FE model enables to verify the effectiveness of the proposed design configuration as well as the selected material for the MR damper components. In addition, the equation of transmitted torque has been derived and utilized to evaluate the MR damper performance. In order to obtain the optimum geometric dimensions of the designed MR damper, an optimization problem has been formulated. The combined Genetic Algorithm (GA) and Sequential Quadratic Programming (SQP) have been employed to accurately capture the global optimum solution.
An experimental test set up has been designed to evaluate the fabricated rotary MR damper performance by measuring the generated damping torque and to validate simulation results obtained from the model.
Subsequently, the hybrid torsional MR damper incorporating both conventional CPVA and rotary MR damper has been proposed. The CPVA has been connected to the cylindrical housing of the MR damper. The governing equations of motion of the system consisting of a rotor with attached hybrid torsional dampers have been derived to evaluate the performance of the system under current off and maximum current applied to the MR damper’s electromagnet. The results are also compared with those obtained from rotor systems with only attached CPVA and rotary MR damper.
Finally, a feedback control system using the semi-active skyhook control algorithm has been developed to adaptively control the proposed hybrid torsional damper under varying external excitations. It has been shown that the suggested closed-loop feedback control algorithm can significantly improve the damper performance compared with the open-loop (current off and on) system.