Vibration Isolation Problem Research Articles

Programmable hardening and softening cubic inductive shunts for piezoelectric structures: Harmonic balance analysis and experiments

It has been well explored in the literature that intentionally introduced (designed) nonlinearities offer significant advantages in vibration absorption and isolation problems. In the context of using piezoelectric shunt damping for vibration attenuation in flexible structures, synthetic impedance circuits with digital control enable precise tuning capabilities and eliminate the need for bulky analog circuit components when targeting low frequencies, and they have been studied mostly for linear circuits. In this work, we explore nonlinear synthetic impedance-based Duffing shunts with hardening and softening nonlinearities, connected to a cantilever under base excitation in its geometrically and materially linear regime. We demonstrate a shunt of nonlinear impedance equivalent to a positive or negative cubic inductor connected in parallel to a linear inductor and a linear resistor. This shunt, along with the inherent piezoelectric capacitance, provides digital analog of a hardening- or softening-type nonlinear stiffness, linear stiffness, linear damping, and mass, as a synthetic Duffing circuit. Electromechanical modeling of a piezoelectric cantilevered beam shunted to the Duffing oscillator with hardening or softening inductance is performed. Numerical simulations for single-term and multi-term harmonic balance solutions are performed for periodic response. These approximate analytical predictions are compared against time-domain numerical simulations and are experimentally validated for various mechanical excitation amplitudes and nonlinear coefficients. Overall, a very good agreement is obtained between the model simulations and experimental results, in addition to demonstrating the unique digital programming capabilities of this nonlinear shunt.

Vibration isolator using graded reinforced double-leaf acoustic black holes - theory and experiment

The acoustic black hole (ABH) has aroused great interest and shown high potential of application in broadband vibration control using a lightweight structure. Yet conventional ABHs still suffer from intrinsic weak structural stiffness and poor broadband low-frequency performance. Besides, there is a lack of effective computational methods for the design of complex or composite ABH structures with practically required properties. In this paper, the vibration isolation of a beam with embedded graded reinforced double-leaf ABH (GRD-ABH) structures is investigated, focusing on improving both broadband low-frequency vibration isolation performance and the structural stiffness. The multibody system transfer matrix method (MSTMM) is proposed to model and simulate the compound ABH beam, which is treated as a multibody system with complex topology. Both the free and forced vibration analysis of the GRD-ABH are conducted and the results are compared with the finite element method (FEM), thus validating the correctness and high computation efficiency of the MSTMM. The results show that the GRD-ABH beam can simultaneously enhance a broadband low-frequency vibration isolation effect and the structural stiffness compared with the conventional periodic reinforced double-leaf ABH beam. The experiment further verified the correctness of the MSTMM and the effectiveness of the vibration isolation effect of the proposed GRD-ABH beam. The proposed theoretical approach and the graded reinforced double-leaf design provide the basis for solving the vibration isolation problem of more complex ABH structures.

Vibration Isolation Characteristics of Impedance-balanced Ship Equipment Foundation under Unbalanced Excitation

A new type of impedance-balanced ship equipment foundation structure based on the principle of impedance balancing using a “discontinuous panel-vibration isolation liquid layer-foundation structure” is proposed to solve the problem of poor low-frequency vibration isolation of the foundation under unbalanced excitation of shipboard equipment. Based on the finite element method, the influence of characteristic parameters of the foundation panel structure on its vibration reduction characteristics under unbalanced excitation is explored. The results show that the vibration isolation level of the impedance-balanced foundation is 10 dB higher than the traditional foundation in the low-frequency band of 10-500 Hz when subjected to combined excitation of concentrated force and moment. Increasing the thickness of the impedance-balanced foundation panel can enhance the isolation effect. Increasing the number of sub-panels can effectively reduce the vibration response of the foundation panel and enhance the isolation performance of the foundation. The connection stiffness between sub-panels has a small effect on the isolation performance of the foundation.

Active Damping, Vibration Isolation, and Shape Control of Space Structures: A Tutorial

This tutorial reviews the author’s contributions to the active control of precision space structures over the past 35 years. It is based on the Santini lecture presented at the IAC-2022 Astronautical Congress in Paris in September 2022. The first part is devoted to the active damping of space trusses with an emphasis on robustness. Guaranteed stability is achieved by using decentralized collocated actuator–sensor pairs. The so-called integral force feedback (IFF) is simple, robust, and effective, and the performances can be predicted easily with simple formulae based on modal analyses. These predictions have been confirmed by numerous experiments. The damping strategy for trusses has been extended to cable structures, and also confirmed experimentally. The second part addresses the problem of vibration isolation: isolating a sensitive payload from the vibration induced by the spacecraft (i.e., the unbalanced mass of attitude control reaction wheels and gyros). A six-axis isolator based on a Gough–Stewart platform is discussed; once again, the approach emphasizes robustness. Two different solutions are presented: The first one (active isolation) uses a decentralized controller with collocated pairs of the actuator and force sensor, with IFF control. It is demonstrated that this special implementation of the skyhook, unlike the classical one, has guaranteed stability, even if the two substructures it connects are flexible (typical of large space structures). A second approach (passive) discusses an electromagnetic implementation of the relaxation isolator where the classical dash-pot of the linear damper is substituted by a Maxwell unit, leading to an asymptotic decay rate of −40 dB/decade, similar to the skyhook (although much simpler in terms of electronics). The third part of the lecture summarizes more recent work done on the control of flexible mirrors: (i) flat mirrors for adaptive optics (AO) controlled by an array of piezoelectric ceramic (PZT) actuators and (ii) spherical thin shell polymer reflectors controlled by an array of piezoelectric polymer actuators (PVDF-TrFE) aimed at being deployed in space.

The research about application of quasi-zero stiffness vibration isolation technology in a large vehicle-mounted optic-electronic equipment

The large vehicle-borne optic-electronic tracking equipment has the characteristics of heavy inertia, complex road condition and wide vibration spectrum. In order to solve the problem of passive broadband vibration isolation for vehicle-mounted moving platform optic-electronic equipment, a combined quasi-zero stiffness vibration isolation scheme is proposed. The vibration of the engine, generator, water cooler and the remaining vibration amplitude, frequency and Yaw of the road after passing the self-vibration isolation system of the vehicle are collected and confirmed by means of calculation simulation and field test. At the same time, the effective load of photoelectric equipment is analyzed by frequency sweeping test, and the corresponding multi-mode frequency points are obtained. According to the characteristics of the special equipment, a quasi-zero-stiffness vibration isolation system is designed to suppress the wide-frequency and high-amplitude vibration and Yaw caused by vehicle-borne vibration source, ground vibration source and resonance point of the equipment, the foundation stability of load equipment under dynamic condition is realized, which provides a condition for solving the problem of high precision and stability tracking which is greatly influenced by vibration. The vibration isolation system can realize the vibration isolation efficiency of 90% in the range of 20 Hz to 2000 Hz under the condition of 60 Km/h three-class highway with 1.5 t photoelectric load, and restrain the deflection caused by unbalance torque and vibration source offset effectively. It can be concluded that the quasi-zero stiffness vibration reduction and isolation combination design can effectively suppress the vibration of the large-scale vehicle-mounted optic-electronic equipment under the condition of moving platform.

A non-smooth quasi-zero-stiffness isolator with displacement constraints

Quasi-zero-stiffness (QZS) mechanism is one of the significant solutions with its distinct advantage to the low-frequency vibration isolation problems in mechanical vibration. However, subject to the limitation of its effective range of very narrow, the strong nonlinearity of the single QZS mechanism under large-amplitude excitation might induce an undesirable large-amplitude vibration or even damage some essential equipment. Therefore, this paper designs a double-layer QZS vibration isolator with displacement constraints to reduce the undesirable large-amplitude vibration. Firstly, the mechanical model of a double-layer QZS vibration isolator with displacement stops is established based on Hertz's contact model (DLQZS-HCM). Subsequently, the incremental harmonic balance method is employed to examine the vibration isolation performance theoretically. The system parameters are then analyzed to explore their influences on the isolation performance. Compared with the double-layer linear isolator (DLL) and double-layer QZS isolator (DLQZS), it is found that the DLQZS-HCM isolator can perform better in both extending the frequency range of vibration isolation and decreasing the peak transmissibility when undergoing large-amplitude excitation. Finally, in order to further enhance the isolation performance at low-frequency levels, feedback control is applied to the DLQZS-HCM isolator. The obtained results reveal that the increasing displacement feedback gain can significantly broaden the vibration-isolation range of the DLQZS-HCM isolator in the frequency area tending to zero.

Study of the external section shape of the static characteristic of the antivibration suspension with a quasi-zero stiffness section

The paper considers the vibration isolation problem of the construction and road vehicles operator’s seat with prescribed sinusoidal displacements of the seat base. This problem is highly relevant, since the road construction vehicles operation with soil, loads, road surfaces, etc. is accompanied by the strong vibrations. The investigation was carried out in terms of the influence of the suspension static power characteristic shape on the maximum vibration acceleration of the seat. Many antivibration mechanisms have a similar static characteristic. Currently, one of the promising directions in the development of the antivibration systems is the implementation of the systems with a quasi-zero stiffness section of the static power characteristic. Such systems are preferred to dampen the low-frequency vibrations. In this paper, we study the systems having a three-segment static characteristic, which middle segment is a horizontal straight line corresponding to a section of quasi-zero stiffness. However, two extreme segments providing the braking and stopping of the mechanism when going beyond the boundaries of the quasi-zero stiffness section were described by Hermite splines with a maximum second-order derivative. The analytical expression of such a two-point spline makes it possible to set not only the function values at two boundary points, but also the values of the first two derivatives of this function at the same points, i.e. to vary the shape of such spline within a wide range. This has made it possible to consider several dozen combinations of such splines having different values of the first derivative at both boundary points, i.e. to study the differently shaped static power characteristics of the antivibration mechanism of the seat under the same sinusoidal influences. The sum of accelerations calculated for a sample of the specified seat base vibrations from the amplitude and time values combinations was used as the assessment and evaluation criterion of various static power characteristics. Furthermore, the amplitude and time values combinations, at which the maximum value of the antivibration mechanism displacements exceeded the limits of at least one of the static characteristics, were excluded from consideration and were not taken into account when calculating the criterion values. The criterion minimum value was found out to be reached at zero value of the first force derivative at the internal boundary points of the external characteristic segments, at the maximum value of the first force derivative at the external boundary points of the external characteristic segments. In this case, the first force derivative has no discontinuities on the entire static force characteristic curve. The given static characteristic is optimal according to the accepted criterion. The value of the acceleration sum criterion can be decreased fourfold in the studied range of the first derivatives from zero to twenty thousand Newton/meter.

Magnetically modulated sliding structure for low frequency vibration isolation

Magnetically modulated sliding structure (MMSS) is proposed and systematically investigated in this paper. The MMSS consists of the sliding beam and a pair of repulsive magnets. The sliding beam can provide negative stiffness, which can be modulated by a pair of repulsive magnets (hardening positive stiffness). The static analysis is completed to fully clarify the modulation mechanism. With the modulation of magnets, the sliding beam can exhibit favorable high-static-low-dynamic stiffness (HSLDS). The dynamic model of the MMSS is developed to evaluate its response when subject to base excitation. The displacement transmissibility is derived by the harmonic balance method (HBM). Transmissibility curves show that the MMSS isolator possesses a low resonant frequency and can isolate vibration in a wide frequency range. The principle prototype is fabricated and tested. The effectiveness of the modulation mechanism in realizing quasi-zero stiffness (QZS) is verified by static experiment. Dynamic tests under periodic, sweep and random excitation demonstrate that the isolator exhibits excellent low frequency isolation performance and the vibration exceeding 4 Hz can be effectively isolated. The MMSS system provides a new approach to solve the problem of low frequency vibration isolation. The modulation mechanism, that is, utilizing hardening stiffness to modulate negative stiffness, is of reference significance for the design of HSLDS isolators.

Implementation of automation in vibration-isolating supports of new type for engines of sea and river vessels

In almost all areas of modern technology, the problem of vibration isolation arises, which is associated with the goal of improving the quality, reliability and productivity of various technical objects. One of the important tasks of shipbuilding is to reduce vibration levels of ship power equipment. This article proposes a non-linear control law for an electromagnetic hydraulic vibration-insulating support (EGVO) for ship power plants (SEP), which allows you to compensate for external harmonic disturbances at the SEP, which leads to an increase in their technological safety. The proposed control law of EGVO has advantages over various control laws of vibration-insulating systems of an active type for SEP. The proposed method can be used to create vibration-isolating active systems for various technical objects. The essential novelty of this method is a consistent synthesis of control laws and the creation of a single process of technological self-organization and control.

Passive and active vibration isolation under isolator-structure interaction: application to vertical excitations

This work studies the influence of a vibration isolator on the response of a flexible base structure. Two strategies are compared: passive and active vibration isolation (PVI, AVI). Although the multiple advantages of AVI over PVI techniques are well known, their effect in the base structure has not to date been compared. This interaction has an important role in the performance of the general control system, especially when the vibration isolation system is not the only system on the base structure or when there are multiple isolators working simultaneously on it. In addition, the structural serviceability of the base structure can also be affected. The analysis of the vibration isolation problem is made from a wide perspective, including the effect that isolator has on the base structure. Hence assuming the base structure is a non-rigid system. The effect of the isolation system on the base response is studied for an extensive range of base structures, thus showing different possible scenarios. The influence is quantified by comparing the peak magnitude response of the base when both passive and active vibration isolation techniques are used. The theoretical results have been corroborated by undertaking experimental tests on a full-scale laboratory structure.

Present problems of vibration isolation in heavy mining machines at long-term cyclic loads

Abstract. An integrated approach was used, including the construction of a mathematical model and the results of lengthy industrial tests of heavy mining machines with rubber elastic bonds. The issues of vibration isolation of heavy machines operating in extreme conditions, i.e. with prolonged cyclic loads and the influence of an external aggressive environment inherent in mining and processing enterprises. As an example, we con-sider vortex mixers with a vibration isolation system containing rubber elements. During long-term operation, the mass of the mixer does not remain constant; its increase is associated with the sticking of the initial product on the moving parts of the ma-chine. The location of such machines in the sinter factory at + 10.4 m, as well as the change in time of rotational symmetry of the drum rotation imposes certain requirements on the vibration isolation system: the system must be "soft" and stable in time, i.e. during 9-10 years of operation, its stiffness and dissipative parameters should not go beyond the permissible values. In order to reduce the aging effect, type 2959 rubber based on natural caoutchouc with a reinforced protective group was used, while the instability of the main mechanical parameters was taken into account in the developed theory of vibration isolation of machines. On the basis of the developed simulation model and the Boltzmann-Volterra integral relations with kernels of relaxation and aftereffect, an equation was worked out, which made it possible to take into account the rubber viscoelastic properties in full volume; in this equation, stiffness operator of elastic suspension in the machine is written by using fractional exponential function of the Yu. Rabotnov's type; on the basis of the mathematical model, the basic parameters of the machine under the study were calculated; in particular, for the vortex mixer, the time dependences of amplitude of the mixer housing vibrations and coefficient of vibration isolation efficiency were calculated with taking into account aging of elastic link material in the ma-chines; the calculation results were compared with the results of industrial tests of the vortex mixer operation lasting for 16 years. The theory and method for calculating vibration isolation systems with rubber elastic links for heavy mining machines were developed with taking into account material structure changes due to the effects of aging. The paper considers an example of calculating the mixer vibration isolation system taking into account rubber aging; the magnitude of the change in time of the main mechanical parameters was obtained experimentally over 16 years. This made it possible to determine temporary changes in the amplitude of oscillations of the mixer body and the coefficient of efficiency of the vibration isolation system. It was shown that the mixer vibration isolation system remained effective for 9-10 years, after which the mechanical characteristics of the rubber went beyond the permissible values and the system lost its functional pur-pose, and the amplitude of the mixer body exceeded the existing sanitary standards.

Research on vibration isolation method of a novel power source

Free-piston linear generator (FPLG) is a novel power source which combines free-piston engines and a linear electric generator. Piston motion and vibration excitation characteristics of FPLG are quite different from the traditional reciprocating engines. This paper aims to clarify the vibration excitation mechanism of FPLG and propose an effective vibration isolation method. The dynamic simulation model of FPLG piston and vibration isolation system are established to solve the special lateral vibration isolation problem, and the vibration excitation mechanism of FPLG is revealed. The influences of mounting parameters on the FPLG vibration is analyzed by the energy decoupling and response surface method. In addition, an effective optimization design method considering comprehensive vibration isolation indices is proposed. By verifying with the simulation model of FPLG vibration isolation system, the proposed method can realize the effective vibration isolation. The analyses will provide guidance for the vibration reduction design of the novel power sources with similar motion characteristics.

Vibration Isolation and Alignment of Multiple Platforms on a Non-Rigid Supporting Structure

In many applications comprised of multiple platforms with stringent vibration isolation requirements, several vibration isolators are employed to work in tandem. They usually must accomplish two objectives: (i) reduce the vibration level of each platform; and (ii) maintain the required alignment with respect to each other or with a fixed reference. If the isolators are located on a rigid supporting structure, the problem can be approached as a classical vibration isolation (VI) problem, in which an increase in damping implies a reduction of vibration level experienced by the platforms. However, there are an increasing number of scenarios in which the dynamic interaction between the isolator and the base structure has the potential to alter the system response and consequently degrade VI performance. In this work, a generalized method to analyze the combined VI and alignment problem, for multiple isolators located on a flexible supporting structure, is proposed. The dynamic interaction between the platforms and the isolators is considered in the control design, and it is proved employing two different functional values that the maximum damping solution is not always the best approach when the dynamics of the supporting structure are considered. Numerical simulations are presented to validate the theory developed and robustness of the proposed control approach is demonstrated.

Calculations of vibration isolation systems by means of SCAS KiDyM in a nonlinear setting

The problem of vibration isolation of a device installed on four three-degree elastic shock absorbers with nonlinear characteristics, as an example of vibration isolation of a discrete system of arbitrary structure with several nonlinear elastic shock absorbers is considered in given paper. An analytical description of mechanical models is applied According to this description a special computer algebra system KiDyM (SCAS KiDyM) constructs differential equations of motion, linearizes inertial and elastic terms by means of elimination of the first small terms, carrying out harmonic linearization of the second one. After getting linear multi-mass mathematical model, the KiDyM software package performs calculations of free vibrations and presents the results in the form of skeletal curves. It allows to determine their sensitivity to the values of elastic and inertial parameters, It makes possible to carry out a cycle of calculations with varying model parameters to achieve optimal characteristics of the vibration protection system by shear and deformation of skeletal curves. An example of the problem analysis solution to the above-mentioned vibration protection system of a device performing spatial vibrations is given. Thus, the system contains 12 nonlinearities. The method for determining the experimental elastic characteristics for specimens of two types of shock absorbers is described. The possibilities of narrowing the spectrum of free vibrations by taking into account the nonlinearity of shock absorbers and the problem of skeletal curves construction of systems with several nonlinearities with generalized coordinates as the main coordinates of the oscillatory system.

Experimental Study of Scissor-like-structure Vibration Isolator

Considering the problem of low-frequency vibration isolation and disadvantages of existing models, an optimized model is established. Based on optimized model, the expression of displacement transmissibility is derived. Then an experimental model of scissor-like-structure vibration isolator (SLS-VI) is established. The comparison of experimental curve and theoretical curve proves the feasibility of model optimization. The effective vibration isolation bandwidth is 10Hz-16Hz which proves the SLS-VI have excellent vibration isolation performance at low frequency. Experimental results are basically consistent with theoretical analysis in displacement transmissibility of the vibration isolator. It proves the correctness of the theoretical analysis of scissor-like-structure at low frequency.

Passive vibration isolation of flexure jointed hexapod: A geometry design method

This paper presents the passive vibration isolation problem for a specific kind of Stewart Platform called flexure jointed hexapod (FJH). For purpose of analyzing the relationship between passive vibration isolation and parameters of the FJH, an existing dynamic model of the hexapod is re-cast appropriately to obtain the transfer function matrix from disturbance to generalized coordinates of the payload. Then, the system natural frequencies and the corresponding damping ratios are derived analytically. To guarantee the effective disturbance attenuation and isolation, a lower bound of the disturbance frequency with respect to the geometric parameters of the FJH is identified. Based on the identified sufficient conditions for disturbance isolation, a new design algorithm for geometry structure of the FJH and coefficients of the parallel spring-damping mechanism in struts is proposed. Finally, numerical simulation results are provided to demonstrate effectiveness of the proposed design algorithm.

УРАВНЕНИЯ ПРОСТРАНСТВЕННОГО ДВИЖЕНИЯ ТВЕРДОГО ТЕЛА С ПОДАТЛИВЫМ КРЕПЛЕНИЕМ К ФУНДАМЕНТУ (ЗАДАЧА АМОРТИЗАЦИИ В ПРОСТРАНСТВЕ)

The task of fastening equipment, especially ship equipment, is considered important in conditions of vibration and shock. Equipment can be mounted on shock absorbers. These shock absorbers solve the problems of vibration isolation and shock protection. The classic case is the use of rubber-metal shock absorbers. The equipment can be attached to the foundation with bolts and dowels. In this case, the bolts mustn't collapse and the joints do not open during shock. An interesting case is an attachment, the fastening of which should not be destroyed. Attachments are usually attached by bolts, the destruction of which is not permissible. In the case of plastic deformation of the bolts they can be tightened, and then replacing the collapsed shock absorber is not easy. The condition of the fastening devices can be investigated by modeling, using computer technology, the movement of the unit. The use of computer technology is justified by the cumbersomeness of the task, the nonlinear characteristics of rubber-metal shock absorbers, and bolts in the case of plastic deformations. Typically, when modeling the movement of shock-absorbing equipment, they are limited to a flat task or a case of hard keys. To solve the spatial problem, we introduce three coordinate systems. One system is non-mobile and connected to the foundation. Two other coordinate systems have a beginning at the center of gravity of the unit. The axes of one of these systems are parallel to the axes of the system associated with the foundation. And the other of these systems are rigidly connected to the unit. At the initial moment, in case of rest, all three systems coincide. For the general case of motion, Euler angles can be used, but due to the small movements of the equipment, accuracy is lost. Indeed, the intersection line of the planes determining the Euler angles is determined with an error (the case of almost parallel planes). To solve this problem, the authors used the angles between the axes associated with the equipment and the foundation plane. Then, through these angles, Euler angles were expressed and expressions were obtained that allow the use of numerical methods to solve the equations of motion.

A Control Strategy of Actively Actuated Eccentric Mass System for Imbalance Rotor Vibration

This paper explores the new control strategy of an actively actuated eccentric mass system (AAEMS) for cancelling the rotor imbalance vibration. The AAEMS consists of an eccentric mass with an actuator that actively moves around the circular guided track attached to the rotating rotor thus can generate an effective centrifugal force perpendicular to any tangential direction of the guided circular trajectory. Therefore, once the magnitude and angular position of the inherited static imbalance of the rotor are identified, this actively controlled system can be dispatched to the target angular position(s) where the effective centrifugal force due to rotor imbalance is completely or partially removed. This novel device is currently available and widely used in the vibration isolation problem. However, the study of its control strategy is quite limited, thus, herein, we proposed a new possible control technique, guaranteeing both the robust vibration isolation performance and less control power consumption. To meet such needs, three primary functions of AAEMS are addressed here. First, two (Extended) Kalman filters were employed to sequentially estimate the unknown imbalance of the rotor and the unknown coulomb friction induced between the contact surface of the circular track and the counter-contacted parts of AAEMS. Second, the position control of the AAEMS is achieved by a linear quadratic regulator (LQR)-based optimal control law, simultaneously minimizing the imbalance vibration of the rotor as well as the power consumption of its own actuator. Third, for the situation where the estimation and control errors are presented, thus causing the failure to an acceptable threshold for imbalance vibration, the trial-error-based fine-tuning angular position control was proposed. The effectiveness of the proposed control strategy was evaluated via the simulations and this study shows the practical potential for addressing the AAEMS-based imbalance vibration elimination.

Acceleration control in active dynamic vibration damper

The paper deals with the planar problem of vibration isolation. The active vibration damper is mounted on an oscillating mass with a vibroactive unit at a point that does not coincide with the mass center and the action of the vibroactive force does not coincide with the mass center. An active dynamic vibration damper is an electrodynamic drive in which the translational movement of the moving mass is carried out according to information about acceleration from an accelerometer mounted on an oscillating mass with a vibroactive unit. The paper gives an assessment of the vibration isolation effectiveness, depending on the mismatch with the mass center of the vibrational force application points, the settings of the active damper and accelerometer.

Wide low frequency bandgap in imperfect 3D modular structures based on modes separation

In this manuscript we experimentally study a modular metamaterial that is able to provide mechanical insulation for elastic wave propagation. Specifically, the structural design is based on the modes separation principle, that entails the presence of ultra-wide bandgap at low frequencies, also in presence of few lattice elements. In this paper, we present a simple manufacturing process for the unit cell realization. This method, however, introduces imperfections given by folding and bonding operations: we demonstrate that upon a careful unit cell design and thanks to modes separation, the presence of defects is not relevant from the dynamical point of view and does not alter the filtering behavior. Moreover, we consider a simple assembly with repetition along a single direction, in order to investigate the metamaterial robustness with respect to the lack of 3D periodicity. Experimental data are compared to numerical simulations demonstrating the advantages of such design for real-life vibration isolation problems.