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A novel six-direction sensor for absolute vibration motion is proposed in this study for the measurement of absolute motions by employing multi-direction quasi-zero-stiffness property. Scissor-like structures with pre-deformed springs are applied symmetrically in the proposed sensor. Based on the mathematical modeling of the proposed six-direction sensor, it is shown that the stiffness and damping properties of the sensor are adjustable nonlinear functions which are dependent on the structural parameters of scissor-like structures. And then, by utilizing bifurcation theory and perturbation method, the structural parameters are optimized for the improvement of measurement accuracy. For the realization of the approximate fixed point for a moving vibration object, the vibration from measurement object to the sensor is isolated, and thus the sensor could obtain the absolute motions. Utilizing the signals obtained by the proposed sensor directly, better vibration/suppression effectiveness is achieved. The results provide a novel and significant six-direction absolute motion measurement method by utilizing multi-direction quasi-zero-stiffness property with noticeable isolation performance only with passive elements.

Classical absorber for vibration suppression of a continuous structure is constructed as a spring-mass oscillator, which only provides coupling force to suppress the vibration of primary structure. In this study, absorber beam is introduced and coupled on the continuous primary beam with magnetic interaction. Thus, the magnetic interaction and coupling bending moment affect the responses of primary beam. Based on the model of the system and Galerkin truncation, the natural frequencies for different magnetic parameters are obtained, which demonstrates that the fundamental frequency can be reduced to zero and the vibration of primary beam can be suppressed in a wide frequency band. Considering the vibration suppression on frequency band, we propose two criteria to evaluate the vibration suppression effect: one is the width of band for vibration suppression and the other is the width for vibration absorption. The two criteria not only show the vibration reduction effect but also correspond to different vibration suppression mechanism. Due to the advantages of zero fundamental frequency induced by the proposed magnetic interaction coupling and wide vibration suppression frequency band, utilizing absorber beam in vibration suppression of continuous structure has potential applications for flexible aim in the fields of manufacturing and aerospace.