Host structures are highly susceptible to environmental disturbance. For safe, reliable and efficient operation, different control methods have been proposed. Despite superior control performance, practical applications of active control methods are limited due to their complexity, high power consumption, instability and overall high cost. As a promising alternative, passive and semi-active control techniques have been extensively studied. In particular, the shunt damping strategy has been identified as a promising method for vibration enhancement performance attributed to its high stability and low power consumption advantages. Moreover, it does not require sensors to operate, thereby cost-effective.
Previous findings revealed that the viscous damping induced by the resistive shunting could effectively damp the mechanical vibration, allowing for optimal tunning of resistive and inductive shunting to structural resonances with characteristics similar to those of mechanical vibration absorbers. Similarly, electromagnetic shunt damping (EMSD) has demonstrated promising results towards effective vibration control. However, most of the existing studies concentrate on linear damping while maintaining the electromagnetic coupling coefficient constant. Additionally, the vibration attenuation reportedly deteriorated in the isolation region despite improving in the resonance region. Therefore, the challenges can be addressed using nonlinear damping, considering the differences between the damping in isolation and resonance regions.
Typically, nonlinear damping can enhance the vibration isolation in the resonance region without necessarily compromising the affecting its corresponding performance enhancement in the isolation regions. Moreover, nonlinear vibration isolators (NVIs) exhibit quasi-zero stiffness and static-low-dynamic stiffness characteristics desirable for effective vibration control. Motivated by the previous findings, Dr. Hongye Ma and Professor Bo Yan from Zhejiang Sci-Tech University investigated the damping and mass effects of nonlinear-EMSD on the vibration isolation performance improvement of NVIs based on magnetic spring. Specifically, the authors explored the potential use of negative resistance and inductance to tune the jump frequency and widen the vibration isolation band of NVIs. The work is currently published in the journal, Mechanical Systems and Signal Processing.
In their approach, they started by exploring the mass and damping mechanisms of nonlinear-EMSD considered crucial in modeling and optimizing the performance of NVIs. Equivalent nonlinear damping and mass were realized through an electromagnetic structure design comprising two permanent magnets and two coils. On the other hand, the stability and transmissibility of NVI with N-EMSD were computed using a combination of the harmonic balance method (HBM) and Jacobian matrix. The damping and mass effects of NVIs with nonlinear-EMSD were verified via parameter analyses, theoretical and experimental modeling. Lastly, experimental results and the performance between linear and nonlinear-EMSD were compared to provide more insights into the vibration attenuation enhancement of nonlinear-EMSD.
The results demonstrated the key role of the inductance comprising the shunt circuit in changing the equivalent nonlinear jump frequency and mass frequency of the NVI. However, this approach was quite different from that used in conventional methods involving dynamic stiffness. Whereas the optimal inductance was reportedly less than zero, the vibration isolation performance deteriorated at large inductances values. In addition, the frequency voltage of the circuit was twice the displacement frequency and was different from that of L-EMSD. Furthermore, the nonlinear damping realized by N-EMSD improved the vibration isolation performance of NVIs in a wideband than that produced by linear damping.
In summary, the new study reported the potential application of nonlinear mass and nonlinear damping effects of nonlinear-EMSD to enhance the vibration isolation performance of permanent magnets-based NVI. The authors observed consistency between the experimental and numerical results, confirming the usefulness of nonlinear damping to overcome the challenges of linear damping for enhanced vibration isolation. In a statement to Advances in Engineering, the authors noted that the study insights would enhance the practical applications of NVIs.
Ma, H., & Yan, B. (2021). Nonlinear damping and mass effects of electromagnetic shunt damping for enhanced nonlinear vibration isolation. Mechanical Systems and Signal Processing, 146, 107010.