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一种含放大机构的负刚度动力吸振器的参数优化

PARAMETERS OPTIMIZATION OF A DYNAMIC VIBRATION ABSORBER WITH AMPLIFYING MECHANISM AND NEGATIVE STIFFNESS

  • 摘要: 在大多数情况下机械振动是有害的,它不仅产生噪声还会降低设备的工作精度和使用寿命.采用正刚度特性的吸振、隔振系统往往难以达到满意效果,这种情况在低频振动控制系统中尤其明显.放大机构与负刚度元件在振动控制领域均表现出良好性能,但是较少有对同时含有放大机构与负刚度装置的动力吸振系统的研究.以Voigt型动力吸振器为基础提出了一种将放大机构应用于含负刚度弹簧元件的动力吸振器模型,对该模型的最优参数进行了研究.首先建立了系统的运动微分方程并得到了其解析解,发现该系统存在两个固定点,利用固定点理论得到了动力吸振器的最优频率比.根据负刚度的特性,在保证系统稳定的前提下得到了最优负刚度比,并推导了系统的近似最优阻尼比.通过数值仿真验证了解析解的正确性.与多种动力吸振器在简谐激励与随机激励下进行了对比,说明了本文模型相比于已有的动力吸振器,能够大幅降低共振振幅、拓宽减振频带并且降低系统的谐振频率,为设计新型动力吸振器模型提供了理论依据.

     

    Abstract: Mechanical vibration is detrimental in most engineering situations, and it may not only generate noise but also reduce the operational accuracy and working life of the equipment. It is generally difficult for vibration absorption and isolation systems with positive stiffness characteristics to achieve satisfactory performance, which becomes noticeable especially in low-frequency vibration control systems. Amplifying mechanism and negative stiffness element both show good performance in the field of vibration control, but the dynamic vibration absorber with both amplifying mechanism and negative stiffness element is rarely studied. Based on the Voigt type dynamic vibration absorber, a dynamic vibration absorber with negative stiffness element using amplifying mechanism is presented, and the optimal system parameters are studied in detail. Firstly, the differential equation of motion is established and the analytic solution of the system is obtained, and it is found that there are two fixed points independent of damping ratio in the amplitude-frequency curves of the primary system. The optimal frequency ratio of the dynamic vibration absorber is obtained based on the fixed-point theory. According to the characteristics of negative stiffness, the optimal negative stiffness ratio is founded under the premise of ensuring the system stability. A simple method is used to derive the approximate optimal damping ratio of the system. The correctness of the analytical results is verified by the comparison with the results by numerical simulation. Compared with other dynamic vibration absorbers under harmonic and random excitations, it could be found that the model with optimal parameters in this paper can greatly reduce the resonance amplitude, broaden the vibration band, and lower the resonance frequency of the primary system. These results may provide theoretical basis for the optimal design of similar dynamic vibration absorbers.

     

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