Mechanical Vibration Isolation Research Articles

4D printing of customizable and reconfigurable mechanical metamaterials

Customizable and reconfigurable mechanical behavior is critical for self-adaptive low-frequency vibration isolators operating in dynamic environments. Herein, the mechanical metamaterials with customizable and configurable geometries, material stiffnesses, cushioning properties, and vibration isolation capabilities are fabricated using a 4D printed multi-material system. The metastructure is characterized by the connection of a flexural beam structure and a collapsible straw structure. At the unit level, the stiffness characteristics are analyzed by geometric and theoretical mechanical models. The effect of geometric parameters and material composition on the stiffness behavior of multi-material metamaterials is investigated. Metamaterials' customizable and configurable characteristics are examined by the quasi-static compression mechanical properties, cushion performances, and vibration isolation capabilities under varying geometric parameters and material compositions. Finally, the reprogrammable stiffness of the metamaterial is demonstrated through the modification of geometric parameters utilizing the shape memory properties in 4D printing. The customizable and configurable metamaterials inspire the next generation of cushioning and vibration isolators, holding significant promise for applications demanding superior vibration isolation performances in dynamic environments.

Adjustable indentation and vibration isolation performances of nacre-like metamaterial

ABSTRACT Along with the living environment, organisms have evolved structures that adapt to specific environments and have better mechanical properties. Bioinspired materials learn from nature and improve their mechanical properties by imitating the structure of living organisms. Based on the 4D printed shape memory polymer and the bioinspired design method, this research proposes a soft and hard phase hybrid bioinspired metamaterial with shape memory effect and programmable mechanical properties. Compared with traditional nacre-like materials, bioinspired materials have adjustable characteristics of mechanical properties, impact resistance, and low-frequency vibration isolation. First, based on the constitutive relation of SMP (Shape memory polymer) material and its numerical simulation, an intelligent bioinspired metamaterial is designed. Subsequently, the mechanical properties and vibration isolation behavior and adjustability performance of multi-scale bioinspired metamaterials are explained by experiments. Finally, the adjustable functional mechanism of the deformation and vibration isolation of the bioinspired metamaterial is described. The research of these bioinspired metamaterials has broad application prospects in the fields of impact protection and low-frequency vibration absorption.

A New Type of Inerter with Easily Adjustable Inertance and Superior Adaptability: Crank Train Inerter

A new type of inerter, called a crank train inerter (CTI), is investigated for structural vibration isolation. The CTI consists of a crank, a linking rod, a gear-pinion box, and a flywheel that generates inertance. It has advantages of quick adjustment of inertance and strong adaptability to other disturbances. First, the inertial force provided by the CTI is linearized and expressed in a simple format; the minimum length of linking rod and crank are obtained for a CTI operating linearly under various deformed configurations. Then, the motion equation of the coupled structure-CTI system is formulated, and transmissibility is analyzed. Laboratory experiments are next carried out to verify the CTI’s mechanical property and vibration isolation performance. It is shown that the inertance of the CTI obtained in the tests agrees well with the analytical result. CTIs can significantly decrease the amplitude-frequency responses at the fundamental frequency but cannot achieve vibration isolation in a full frequency range. Finally, the seismic control effect of base-isolated buildings with and without CTI is numerically studied. An optimal design method of the CTI is proposed, and the story drift ratio and deformation of the isolation layer can be reduced simultaneously with the optimal inertance. The installation methods of CTIs for buildings are also presented.

Design and Mechanical Performance Analysis of Vibration Reduction and Isolation Platform

Vibration reduction and isolation platform is a device that can effectively reduce or isolate vibration in space environment. It is widely used in precision equipment fields such as mechanical structure, precision machining, optical instruments. A three-stage mechanical active vibration reduction and isolation platform is designed. The static analysis is carried out using professional software. The research results show that when 3000N concentrated load is applied on the working platform, the maximum deformation is 0.0073mm, the maximum stress is 2.82MPa. And when 4000N asymmetric load is applied, the maximum deformation is 0.048mm, the maximum stress is 200MPa. The modal analysis results show that the first frequency is 40Hz and the sixth frequency is 180Hz. The product has certain engineering application value.

Figure of Merit Enhancement of Laterally Vibrating RF-MEMS Resonators via Energy-Preserving Addendum Frame.

This paper examines a new technique to improve the figure of merit of laterally vibrating RF-MEMS resonators through an energy-preserving suspended addendum frame structure using finite element analysis. The proposed suspended addendum frame on the sides of the resonant plate helps as a mechanical vibration isolator from the supporting substrate. This enables the resonator to have a low acoustic energy loss, resulting in a higher quality factor. The simulated attenuation characteristics of the suspended addendum frame are up to an order of magnitude larger than those achieved with the conventional structure. Even though the deployed technique does not have a significant impact on increasing the effective electromechanical coupling coefficient, due to a gigantic improvement in the unloaded quality factor, from 4106 to 51,136, the resonator with the suspended frame achieved an 11-folds improvement in the figure of merit compared to that of the conventional resonator. Moreover, the insertion loss was improved from 5 dB down to a value as low as 0.7 dB. Furthermore, a method of suppressing spurious mode is demonstrated to remove the one incurred by the reflected waves due to the proposed energy-preserving structure.

ПРОЕКТУВАННЯ БІЛЬШОГО ВМІСТУ КВАДКОПТЕРІВ НА КОНТРОЛЕРАХ СІМЕЙСТВА PIXHAWK CUBE

The quadrocopter’s design and configuration that capable to carry a payload of up to 30 kg based on the Pixhawk 2 Cube flight controller using Arducopter ver.4.1.5 firmware for FMUv3 devices was completed in the paper. For ensuring a flight range of 10-12 km, the using of 44000 mAh battery and payload of 10-15 kg is recommended. It has been established that when building large-sized copters, before setting up the PID controller, it’s necessary to pre-configure the parameters that are used by the PID controller. The failure to do so will often cause the aircraft to crash on its first flight. These are motor thrust linearization parameters, acceleration values for different axes and filters that go to the input of the PID controller. Experimentally tested the stability of the quadrocopter’s flight in windy weather in navigation modes for firmware Arducopter ver.4.1.5. At wind speeds up to 10 m/s with gusts up to 14-15 m/s, the flight stability was noted in automatic mode and in automatic return to the starting point mode. The high accuracy of the operation of the Ardupilot firmware navigation system was established when the cargo drop point was reached in automatic mode. The error was no more than 1.0-1.5 m at wind speed of 6-7 m/s. The effectiveness of mechanical vibration isolation for flight controllers of the Pixhawk Cube family has been experimentally established. When installing them on the frame of the copter, there is no need to use mechanical vibration decoupling. However, taking into account the low frequency of the frame oscillations from the operation of the propeller group (about 30 Hz), it’s necessary to design the frame with the frequency of natural oscillations outside this range. The using of software dynamic notch filters to reduce the impact of vibrations from running motors on the readings of the accelerometer and gyroscope is considered. On the frame of 2000 mm quadrocopter, it’s shown that such filters significantly reduce the amplitude of not only the detected fundamental frequency, but also their harmonics. The various ways of setting up actuators controlled by servos and relays for dropping loads, switching operating modes by video systems, switching on and off spraying mechanisms when using such drones in agriculture are considered.

Acoustic decoupling for structural elements by affixed supports - inherent contradiction or perfect complement? Restrained vibration isolation supports - a critical review

Restrained vibration isolation supports balance efficient isolation performance and stability for the supporting body under present loads. Necessary and beneficially for noise and vibration isolation applications with stringent stability requirements, such as full building isolation with potential uplift, interior partition sway bracing, curtain walls, elevator rail isolation, and mechanical vibration isolation, the performance of restrained vibration isolators are often misunderstood or oversimplified. This paper investigates the general vibration isolation theory used to create the analytical model for restrained isolation supports, intricacies of vibration isolation materials which may cause reality to diverge from well-known models, comparison of theory to laboratory testing, and a review of common uses/applications for these types of vibration isolation solutions, and recommendation to avoid undesired results from common pitfalls associated with restrained isolation supports implementation and installations.

3-DoF zero power micro vibration isolation via linear matrix inequalities based on [formula omitted] and [formula omitted] control approaches

Zero-power micro vibration isolators based on hybrid electromagnets, consisting of coils and permanent magnets, have potential usage in many industrial and academic fields, such as space laboratory operations in orbit, micro-nano assembly, clean room design, bio-engineering, stewart platforms, transportation, semiconductor manufacturing, suspension system design, and robotic surgery platforms etc. due to providing mechanical contact free micro vibration isolation with comparatively low energy consumption. Classical controllers optimized in time-domain do not show satisfying disturbance rejection performance for multi-directional mechanical disturbances varying at different frequencies. To tackle this problem, optimization techniques in frequency-domain are needed. In recent years, linear matrix inequality (LMI) based controllers have received lots of attention and become very popular due to their ability to satisfy multi-objective frequency-domain requirements. However, an experimental research including LMI based H∞ and H2 feedback controllers for a zero-power 3-DoF micro vibration isolator has not been conducted so far. In this study, H∞ and H2 controller types are employed to minimize the H∞ and H2 norms of both ground and direct disturbances for 3-DoF micro-scale vibration isolation with zero-power objective. Moreover, the experimental setup has been designed and manufactured to meet aforementioned goals. The design parameters of the experimental setup are explicitly given. The effectiveness of the proposed LMI structures for 3-DoF micro vibration isolation with zero-power problem is shown with the experimental results.

Active Vibration Isolation of a Maglev Inertially Stabilized Platform Based on an Improved Linear Extended State Observer

An inertially stabilized platform is subject to the vibration force and moment from its support base, and low-frequency vibrations cannot be eliminated by mechanical vibration isolation. Combining gimbals with magnetic bearings instead of mechanical bearings, a maglev inertially stabilized platform (MISP) is characterized by no friction or an active vibration control capability. In this paper, an improved linear extended state observer (LESO) replacing displacement error with next-order error is proposed to estimate the low-frequency vibration and improve the estimation accuracy. An active vibration isolation control method is then designed to realize cancellation compensation on the MISP. Finally, a simulation example is presented to validate that the proposed measures can effectively eliminate the low-frequency vibration force transmitted from the base and ensure the stability of the MISP.

4D printed zero Poisson's ratio metamaterial with switching function of mechanical and vibration isolation performance

The unusual properties of mechanical metamaterials are determined by the configuration of artificial periodic structures. However, the mechanical performance of conventional metamaterials is irreversible and cannot perceive and respond to the changes in the environment. In present study, a zero Poisson's ratio metamaterial with intelligent switching mechanical properties and vibration isolation effect is proposed. Based on a 4D printing method of shape memory polymer, this metamaterial is created that can sense temperature changes and switch mechanical properties. The macroscopic deformation and the morphology change of the metamaterial during compression tests are analyzed using experimental and finite element methods. The irregular buckling distortion of the metamaterial is eliminated by cylindrical design, and controllable and adjustable local deformation and stress-strain curve are achieved based on microstructure gradient design. Subsequently, this work focused on the vibration isolation performance of metamaterials, and found fascinating shock absorption performance. Compared with traditional linear spring, this metamaterial spring can effectively reduce the vibration amplitude of certain frequency bands before reaching the resonance peak, which provides a new realization method for low-frequency vibration isolation design.

Identification and Removal of Non-acoustic Noise in Towed Array Sonar Using F-Κ Transform for Enhanced Torpedo Detection

Low frequency passive towed array sonar is an essential component in a torpedo detection system for surface ships. Compact towed arrays are used for torpedo detection and they will be towed at higher towing speeds compared to conventional towed array sonars used for surveillance. Presence of non-acoustic noise in towed array sensors at higher towing speeds degrades torpedo detection capability at lower frequencies. High wavenumber mechanical vibrations are induced in the array by vortex shedding associated with hydrodynamic flow over the array body and cable scope. These vibrations are known to couple into the hydrophone array as nonacoustic noise sources and can impair acoustic detection performance, particularly in the forward end fire direction. Lengthy mechanical vibration isolation modules can isolate vibration induced noise in towed arrays, but this is not recommended in a towed array which is towed at high speeds as it will increase the drag and system complexity. An algorithm for decomposing acoustic and non-acoustic components of signals received at sensor level using well known frequency-wavenumber transform (F-K transform) is presented here. Frequency-wavenumber diagrams can be used for differentiating between acoustic and non-acoustic signals. An area of V shape is identified within the F-K spectrum where acoustic energy is confined. Energy outside this V will highlight non-acoustic energy. Enhanced simultaneous spatio-temporal and spatio-amplitude detection is possible with this algorithm. Performance of this algorithm is validated through simulation and experimental data.

Analysis and Design of Magnetic Levitation and Mechanical Spring Compound Vibration Isolation Control System

In this paper, the magnetic levitation and mechanical spring compound vibration isolation control system is designed by applying maglev active control on the basis of mechanical vibration isolator. The system can effectively solve the problems of fixed structure parameters and poor environmental adaptability of passive vibration isolators, and can be applied to the anti-vibration protection of precision instruments in complex environments. This paper analyses the mechanism and characteristics of maglev vibration isolation, deduces the dynamic model of the system, discusses the design of the active vibration isolation control strategies, and carries out several simulation experiments of vibration isolation in different environments. The results show that the design scheme of the system is reasonable and feasible.

Dynamic research on a low-frequency vibration isolation system of quasi-zero stiffness

The paper describes an establishment of dynamic characteristics of the newly created passive mechanical system for isolation of low-frequency (0.7 Hz–50 Hz) vibrations. The many metrological means are sensitive to mechanical vibrations and acoustic noise of low frequency. Such may appear both outside and inside a building, i.e. may be caused by wind, heating, aeration, air conditioning equipment, moving vehicles and other. In the paper, description of the theoretical and experimental tests is provided. The obtained dynamic characteristics (transmissibilities) of the passive mechanical low-frequency vibration isolation system show that such a system is able to isolate vibrations effectively in the frequency range of 0.7 Hz–50 Hz. The results of the experimental tests support the results of the theoretical research.

Phononic band gap with/without a defect layer in periodic and quasi-periodic structure

In the present paper, we focus on the ability of phononic crystals to treat the different elastic wave's frequencies at the same structure. Changing the periodicity of the structure from perfect and defect structure can modify the width/position of phononic band gaps. By comparing between one, two and four defect layers inside perfect ones, interesting results concerning the localized peaks with the band gaps were obtained. Since the width of band gaps and the number of localized peaks is increased by increasing the defect layers. Moreover, we pay more attention in comparing the band gaps between periodic and quasi-periodic structures. A multifunctional PnC structure could be obtained depend on periodicity and materials types were investigated and discussed. These results may be of potential importance in many engineering applications such as mechanical filters and vibration isolation devices.

Dynamics of Vibration Isolation System with a Ball Vibration Absorber

The forced vibrations of a mechanical vibration isolation system consisting of a ball vibration absorber (BVA) with linear viscous resistance and a movable carrier body under an external harmonic load are considered. Appell’s formalism is used to formulate and numerically solve the equations of combined motion of the heavy ball without sliding in the spherical cavity of the carrier body. The frequency response of the system and curves of the maximum amplitude of vibrations of the carrier body versus the radius of the spherical cavity and the coefficient of viscous resistance of the BVA are plotted. The conditions and constraints on the rolling of the heavy ball in the spherical cavity without sliding are established.

Mechanical and vibration isolation behaviour of acrylonitrile-butadiene rubber/multi-walled carbon nanotube composite machine mounts

ABSTRACTAn effective analytical-experimental test method is used in the current work to characterize the vibration isolation performance of nitrile-butadiene rubber (NBR) reinforced with multi-walled carbon nanotubes (MWCNTs). A series of specimens were manufactured with 10 different NBR/MWCNTs concentrations (0 to 20wt% MWCNTs). In order to determine the static compression stiffness and hysteresis of the mounts, compression and cyclic tests were conducted. The vibration isolation properties were determined through the analysis of the transmissibility of a suitably designed test system. NBR’s mechanical properties and vibration isolation properties were improved with the addition MWCNTs, suggesting that the enhancement of NBR with MWCNTs was rather effective. Considering the obtained results, the dynamic stiffness of NBR and its capacity to isolate vibration can be adjusted by controlling the proportion of MWCNTs.

Design and analysis of strut-based lattice structures for vibration isolation

This paper presents the design, analysis and experimental verification of strut-based lattice structures to enhance the mechanical vibration isolation properties of a machine frame, whilst also conserving its structural integrity. In addition, design parameters that correlate lattices, with fixed volume and similar material, to natural frequency and structural integrity are also presented. To achieve high efficiency of vibration isolation and to conserve the structural integrity, a trade-off needs to be made between the frame’s natural frequency and its compressive strength. The total area moment of inertia and the mass (at fixed volume and with similar material) are proposed design parameters to compare and select the lattice structures; these parameters are computationally efficient and straight-forward to compute, as opposed to the use of finite element modelling to estimate both natural frequency and compressive strength. However, to validate the design parameters, finite element modelling has been used to determine the theoretical static and dynamic mechanical properties of the lattice structures. The lattices have been fabricated by laser powder bed fusion and experimentally tested to compare their static and dynamic properties to the theoretical model. Correlations between the proposed design parameters, and the natural frequency and strength of the lattices are presented.

Dynamic Mechanical Characterization of Polyurethane/Multiwalled Carbon Nanotube Composite Thermoplastic Elastomers

ABSTRACTAn effective analytical–experimental test method is used in the current work to characterize the vibration isolation behavior of thermoplastic polyurethane multiwalled carbon nanotube nanocomposites with five different concentrations. To determine the static compression stiffness and hysteresis of the specimens, compression and cyclic tests were conducted. The vibration isolation properties were determined through the analysis of transmissibility of a suitably designed test system. Thermoplastic polyurethane’s mechanical properties and vibration isolation properties were improved with the addition of multiwalled carbon nanotubes. Considering the obtained results, the dynamic stiffness of thermoplastic polyurethane and its capacity to isolate vibration can be adjusted by controlling the proportion of multiwalled carbon nanotubes.

Stochastic resonance in a nonlinear mechanical vibration isolation system

This paper concerns the effect that a stochastic resonance can have on a vibration isolation system. Rather than reducing the transmitted force, it is shown that it is possible to significantly mask the component of the force transmitted though the isolator, when the system is excited harmonically. This can be achieved by adding a very low intensity of random noise to the harmonic excitation force. The nonlinear mechanical vibration isolation system used in the study consists of a vertical linear spring in parallel with two horizontal springs, which are configured so that the potential energy of the system has a double-well. Prior to the analytical and numerical study, an experiment to demonstrate stochastic resonance in a mechanical system is described.

Nested trampoline resonators for optomechanics

Two major challenges in the development of optomechanical devices are achieving a low mechanical and optical loss rate and vibration isolation from the environment. We address both issues by fabricating trampoline resonators made from low pressure chemical vapor deposition Si3N4 with a distributed Bragg reflector mirror. We design a nested double resonator structure with 80 dB of mechanical isolation from the mounting surface at the inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower frequencies in agreement with the design. We reliably fabricate devices with mechanical quality factors of around 400 000 at room temperature. In addition, these devices were used to form optical cavities with finesse up to 181 000 ± 1000. These promising parameters will enable experiments in the quantum regime with macroscopic mechanical resonators.