Semiactive vibration reduction through stiffness modulation

在文献中，半主动减振方法通常与主动和被动方法很好地结合在一起。最重要的是，相对较低的能量需求往往被放在前台。其有效性(幅度减小、避免共振)和在较宽频谱中应用或适应不同频率范围的可能性与现有方法相当。通过循环刚度变化来减振--即以与当前普遍振动相似的频率改变结构刚度--也属于半主动方法的范畴，因为它涉及修改系统参数。然而，必须考虑到，通常只有通过改变势能才能实现刚度的改变，因此必须进行功。特别是对于循环变化，因此这种方法是否能达到半主动方法所赋予的能效是值得怀疑的。在目前的研究状态下，由于使用额外的耗散元件，能量方面要么没有被考虑到，要么被偏向了。因此，对循环刚度变化的减振效率的评估仍然悬而未决。我们自己的初步工作表明，特别是刚度变化的空间分布在所要执行的功中起着决定性的作用。在刚度均匀变化的情况下，减幅效应可以很大程度上归因于执行器的负功。另一方面，通过局部变刚度调整，不仅可以从系统中提取能量，而且首先可以将振动模式重新分配到其他模式。这种能量重新分布的优点是在吸能模式的高频区更好地利用了结构的固有阻尼性。因此，该方法省去了很大一部分要做的工作，并且在能量方面表现出与经典半主动方法相似的效率。该项目的长期目标是开发一种程序，以最大化半主动效应(将能量重新分配到合适的模式)，从而提高该方法对连续系统的效率。作为一种改变刚度的机制，特别考虑了预应力和形状适应。然而，刚度的时间和空间变化将是主要的焦点。在拟建工程中，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.