Semiactive vibration reduction through stiffness modulation

半主动减振方法通常在文献中与主动和被动方法之间的良好折衷相关联。最重要的是，相对较低的能源需求往往被放在前台。其有效性（振幅降低、避免共振）和在宽频谱中应用或适应不同频率范围的可能性与有源方法相当。通过循环刚度变化的减振--即以与当前主要振动相似的频率改变结构刚度--也福尔斯半主动方法的范畴，因为它涉及系统参数的修改。然而，必须考虑的是，刚度的变化通常只能通过势能的变化来实现，因此必须做功。特别是对于循环变化，因此，这种方法是否能够达到半主动方法的能量效率是值得怀疑的。在目前的研究状态下，由于使用了额外的耗散组件，能量方面要么没有被考虑，要么有偏见。因此，对周期刚度变化的减振效率的评估仍有待进行。我们自己的初步工作已经表明，特别是刚度变化的空间分布在所要完成的工作中起着决定性的作用。在刚度均匀变化的情况下，致动器的负功可以显著地降低振幅。另一方面，通过局部变化的刚度调节，能量不仅可以从系统中提取，而且首先可以从振荡模式重新分配到其他模式。这种能量再分配的优点是能更好地利用结构在吸能模态高频区的固有阻尼特性。因此，要做的工作的很大一部分被省略，该方法显示出类似于经典的半主动方法的效率，也根据精力充沛的方面。该项目的长期目标是开发一种程序，以最大限度地提高半主动效应（能量重新分配到合适的模式），从而提高连续系统的方法的效率。作为一种改变刚度的机制，预应力和形状适应被特别考虑。然而，刚度的时间和空间变化将是主要的焦点。在拟建项目中，将对这些参数进行分析，确定相应的规律，最终建立设计规则和优化公式。

Semi-active methods for vibration reduction are usually associated in literature with a good com-promise between active and passive methods. Above all, the comparatively low energy require-ment is often placed in the foreground. The effectiveness (amplitude reduction, avoidance of reso-nances) and the possibilities for application in a wide frequency spectrum or adaptation to differ-ent frequency ranges are on a comparable level to active methods. Vibration reduction by means of cyclic stiffness changes - i.e. changes in the structural stiffness with a similar frequency to the currently prevailing vibration - also falls by definition into the area of semi-active methods, since it involves the modification of a system parameter. However, it must be considered that a change of the stiffness can usually only be achieved with a change of the potential energy and consequently work must be performed. Especially for cyclic change, it is therefore questionable whether such an approach can live up to the ascribed energy efficiency of semiactive methods. In the current state of research, energetic aspects are either not considered or biased due to the use of additional dis-sipative components. An evaluation of the efficiency of cyclic stiffness changes for vibration reduc-tion is therefore still pending. Our own preliminary work has shown that, in particular, the spatial distribution of stiffness chang-es plays a decisive role in the work to be performed. With a homogeneous change of stiffness, am-plitude-reducing effects can be significantly attributed to a negative work of the actuator. With a locally varying stiffness adjustment, on the other hand, energy can not only be extracted from the system, but above all redistributed from the oscillating mode to other modes. This energy redistri-bution has the advantage of making better use of the inherent damping properties of the structure in the higher-frequency region of the energy-absorbing modes. Thus, a large part of the work to be done is omitted and the method shows an efficiency similar to that of classical semiactive methods also under energetic aspects. The long-term goal of the project is to develop a procedure to maximize the semiactive effect (re-distribution of energy to suitable modes) and thus to increase the efficiency of the method for con-tinuous systems. As a mechanism for changing the stiffness, pre-stressing and shape adaptation are considered in particular. However, the temporal and spatial variation of stiffness will be the main focus. These parameters will be analyzed in the proposed project, corresponding laws will be determined and finally design rules and optimization formulations will be established.