Abstract
Negative inertia is an unusual and counter-intuitive property of matter, extensively investigated in some of the most exotic branches of physics and engineering at both macroscopic and microscopic levels. Such an exotic property promises a wide range of applications, from Alcubierre drive to acoustic wave manipulation. Here, a novel approach to the realization of negative inertia and the concept of negative-inertia converters are introduced for both translational and rotational motion. The proposed devices, capable of exhibiting negative mass and negative moment of inertia, base their operational principle on actuating the loading inertia, concealed within the housing of the device, synchronously with the displacement of the housing itself. Negative-inertia converters share many similarities with negative-impedance converters, including their proneness to instability. Thus, an equivalent circuit model of the proposed devices is developed and simulated in lossless and lossy environments. Friction, unavoidable in every practical system, is found to be the main cause of instability. The derived closed-form stability condition suggests that the effective inertia of a system containing a negative-inertia converter must remain positive to ensure the stability. Despite this limitation, negative-inertia converters may become the key elements in applications requiring reduction of an object’s inertia.
Highlights
Mass is commonly defined as a measure of an object’s inertia
The derived closed-form stability condition suggests that the effective inertia of a system containing a negative-inertia converter must remain positive to ensure the stability
In this article we transfer the concept of electrical negative-impedance converters (NICs) to mechanical systems and propose novel concept of mechanical negative-inertia converters (NICs), able to produce negative mass in a fundamentally different manner compared to acoustic metamaterials
Summary
Mass is commonly defined as a measure of an object’s inertia. In a sense, it represents the object’s resistance to acceleration. The effective parameters of all passive structures vary with frequency This limitation is a direct consequence of Foster’s reactance theorem [18] and comes from the resonant nature of passive metamaterials. NICs have been known since the era of vacuum tubes [19] They are active devices that transform a passive impedance into its negated and scaled counterpart that behave as fictitious negative element. Such an element requires an additional power source and does not obey Foster’s reactance theorem [18], and it is known as a non-Foster element. In this article we transfer the concept of electrical NICs to mechanical systems and propose novel concept of mechanical negative-inertia converters (NICs), able to produce negative mass in a fundamentally different manner compared to acoustic metamaterials.
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