Integrated vibration isolation and actuation via dual nonlinear stiffness regulation

Abstract

Integrating vibration isolation and actuation is superior, enabling enhanced vibration isolation performance while attaining controllable load position and attitude. Herein, a novel actuatable quasi-zero stiffness (QZS) vibration isolator (AQVI) is proposed and systematically investigated. The stiffness nonlinearization for QZS is fulfilled by paralleling nonlinear electromagnetic negative and positive stiffness structures. This configuration gives rise to an interesting behavior, that is, the rated load and equilibrium position are tailorable via dual nonlinear stiffness regulation, rendering the load actuatable without a trade-off with the QZS characteristic. The comprehensive static investigation is implemented to fully reveal and verify the dual nonlinear stiffness regulation mechanism. Dynamic governing equations are derived and solved in the cases of dwell and actuation, and it is found that the AQVI is capable of isolating broadband vibrations and tracking prescribed trajectories. Finally, an experimental apparatus is built to evaluate the vibration isolation performance and examine the effectiveness of the load actuation. The sweep excitation test demonstrates that the AQVI has good vibration isolation performance, exemplified by a low resonant frequency of 2.5 Hz and a small isolation starting frequency of 3.6 Hz. The load actuation test validates that the AQVI under open-loop control is competent to actuate the load following the desired trajectory while retaining excellent vibration attenuation. The proposed AQVI provides a novel paradigm for devising QZS isolators that are insensitive to the load and working point, shedding promising light on applications requiring integrated vibration isolation and actuation.