Passive Vibration Isolation Research Articles

Cryogen-free scanning gate microscope for the characterization of Si/Si0.7Ge0.3 quantum devices at milli-Kelvin temperatures

Silicon can be isotopically enriched, allowing for the fabrication of highly coherent semiconductor spin qubits. However, the conduction band of bulk Si exhibits a six-fold valley degeneracy which may adversely impact the performance of silicon quantum devices. To date, the spatial characterization of valley states in Si has remained limited. Moreover, techniques for probing valley states in functional electronic devices are needed. Here, we describe a cryogen-free scanning gate microscope for the characterization of Si/Si0.7Ge0.3 quantum devices at mK temperatures. The newly built instrument is the first cryogen-free scanning gate microscope capable of forming and measuring a quantum dot on a Si/SiGe device with an overlapping gate structure without compromising the ability to host multiple DC and microwave lines for quantum control experiments. The microscope is based on the Pan-walker design, with coarse positioning piezostacks and a fine scanning piezotube. A tungsten microscope tip is attached to a tuning fork for active control of the tip-to-sample distance. To reduce vibration noise from the pulse tube cooler, we utilize both active and passive vibration isolation mechanisms and achieve a root-mean-square noise in z of ∼2 nm. Our microscope is designed to characterize fully functioning Si/Si0.7Ge0.3 quantum devices. As a proof of concept, we use the microscope to manipulate the charge occupation of a Si quantum dot, opening up a range of possibilities for the exploration of quantum devices and materials.

Review on Vibration Isolation Method for Atomic Interference Gravimeter

The cold atomic interference absolute gravimeter is an ultra-precision instrument for measuring absolute gravity acceleration. At present, the highest measurement accuracy can reach the order of micro gamma. It has important application value and research significance in many disciplines, such as geophysics, resource exploration and assisted navigation. Because of its ultra-high precision, the ultra-low frequency micro-vibration noise on the ground has become one of the important factors affecting its accuracy, and it is also the bottleneck of the further development of gravimeter. Firstly, based on the theoretical and experimental results, this paper analyzes the vibration isolation requirements of atomic interference gravimeter. Secondly, it summarizes the research progress of atomic interference gravimeter isolation system and introduces three main isolation methods: passive vibration isolation, active vibration isolation and vibration compensation. Finally, the future development direction of atomic interference gravimeter isolation technology is analyzed and prospected.

Vibration isolation with passive linkage mechanisms

This study is to present a novel way to achieve superior passive vibration isolation by employing a specially designed and compact linkage mechanism. The proposed anti-vibration system has beneficial nonlinear inertia, inspired by swinging motion of human arms, and is constructed with an adjustable nonlinear stiffness system inspired by animal or human leg skeleton. It is shown with comprehensive theoretical analysis and consequently validated by a series of well-designed experiments that the nonlinear stiffness, nonlinear damping and nonlinear inertia of the proposed system are very helpful for significantly reducing resonant frequency and enhancing damping effect in a beneficial nonlinear way. This results in excellent vibration isolation performance with lower resonant frequency and resonant peak of faster decay rate. This study provides an innovative solution to a cost-efficient vibration control demanded in various engineering systems.

A simple and efficient passive vibration isolation system for large loads in closed-cycle cryostats.

We present a system for passive damping of vibrations along three spatial degrees of freedom for cryostats equipped with closed-cycle coolers. The system, designed to isolate a payload of 30kg, consists of two stages of isolation for vibrations in the vertical direction. The first isolation stage incorporates a trapezoidal beryllium copper cantilever blade. The second stage is attached to the blade via a steel wire and consists of four extension springs with an extended length of 370mm. At 1.6K, the stages possess vertical resonance frequencies of 2.1 and 1.3Hz, respectively. The vertical length of the setup with a cumulative length of 580mm also acts as a pendulum with a resonance frequency of 0.65Hz. In the frequency band from 5 to 200Hz, the frequency-integrated acceleration decreased from 6.7 × 10-3 to 4.3 × 10-5 g along the horizontal direction and from 4.3 × 10-3 to 7.2 × 10-5 g along the vertical direction. This corresponds to a reduction in vibrations by factors of 156 and 60, respectively. Overall, we achieve a simple, robust, and cost-efficient vibration isolation system for upgrading standard-type cryostats.

A variable positive-negative stiffness joint with low frequency vibration isolation performance

A new vibration isolation joint with combined positive and negative stiffness is proposed, which also supports multi-directional stiffness adjustment. Two sets of opposed buckling Euler beams are used as the variable stiffness structure. The effective length of the beam is changed by moving the slider, which in turn changes the structural stiffness. In the horizontal direction the structure provides adjustable positive stiffness. In the vertical direction it can provide adjustable negative or positive stiffness. A disk spring with nonlinear stiffness characteristics is used as the load-bearing spring and is connected in parallel with the variable stiffness structure. The static and dynamic characteristics show that the structure has good passive low-frequency vibration isolation performance. By actively moving the slider to change the structural stiffness, the equilibrium position of the system can be changed, active actuation can be performed, and active control of ultra-low frequency vibration isolation can be achieved.

A Passive Vibration Isolator Integrated a Dynamic Vibration Absorber with Negative Stiffness Spring

A Passive Vibration Isolator Integrated a Dynamic Vibration Absorber with Negative Stiffness Spring

Optimal Control of Semiactive Two-Stage Vibration Isolation Systems for Marine Engines

To improve the vibration reduction performance of two-stage vibration isolation systems for marine engines under wide frequency band and multifrequency excitation, the magnetorheological (MR) damper is introduced into the vibration isolation system and an optimal controller is designed. Taking the test results of MR damper dynamic characteristics as sample data, the forward and inverse models of the MR damper are identified by the least square method and neural network (NN) method respectively, and the identification results are applied to semiactive control of the two-stage isolation system. Based on the analysis of vibration source, a six-degree-of-freedom mechanical model of two-stage system based on the MR damper is established. The optimal controller taking the minimum force transmitted from the engine to base as the control objective is designed. The system model and numerical simulation analysis are established using MATLAB. The results show that the isolation effect of optimal control is better than that of passive vibration isolation in the whole frequency band. In addition, good control effect is achieved in the low-frequency resonance region which is most concerned in engineering, which is of great significance to further improve the vibration reduction performance of marine engines.

Innovative elastomeric shear leg mount concepts for quasi-zero stiffness isolation

Passive vibration isolation may be a cost-effective solution to isolate a supported system containing a source and/or receiver from the supporting structure. The standard linear theory suggests a low-stiffness joint to create a mobility mismatch in the transmission path, but this solution may lead to large amplitude motions in the supported system. To achieve both motion control and isolation with the same mount and without compromising either objective, an innovative, nonlinear mount concept is proposed. Taking advantage of geometric nonlinearity for large displacements, a quasi-zero stiffness is generated by exploiting the interaction between the nonlinear mechanisms that govern the motion of a number of inclined shear legs. For example, a three-regime stiffness profile is created, including a medium-stiffness preload regime, a quasi-zero stiffness isolation regime, and a high-stiffness motion control regime. This concept offers significant benefits compared with a more conventional compromise approach in that low-amplitude vibrations are exceptionally isolated while large amplitude transient motions are controlled. Illustrative computational examples will be presented to support the underlying linear and nonlinear design principles. Limiting cases will be discussed as well.

An innovative X-shaped vibration isolation mount with tunable quasi-zero-stiffness property

Passive vibration isolation is always preferable in many engineering practices. To this aim, an innovative, compact, and passive vibration isolation mount is studied in this paper. The novel mount is adjustable to different payloads due to a special oblique and tunable stiffness mechanism, and of high vibration isolation performance with a wider quasi-zero-stiffness range due to the deliberate employment of negative stiffness of the X-shaped structure. The X-shaped structure has been well studied recently due to its excellent nonlinear stiffness and damping properties. In this study, by using of the negative stiffness property within the X-shaped structure, the X-shaped mount (X-mount) can have an obviously larger vibration displacement range which maintains the quasi-zero-stiffness property. A special oblique spring is thus introduced such that the overall equivalent stiffness can be much easily adjusted. Systematic parametric study is conducted to reveal the critical design parameters and their relationship with vibration isolation performance. A prototype and experimental validations are implemented to validate the theoretical results. It is believed that the X-mount would provide an innovative technical upgrade to many existing vibration isolation mounts in various engineering practices and it could also be the first prototyped mount which can offer adjustable quasi-zero stiffness conveniently.

High Damping Passive Launch Vibration Isolation System Using Superelastic SMA with Multilayered Viscous Lamina

Whole-spacecraft launch-vibration isolation systems are attractive for achieving the goal of better, faster, cheaper, and lighter small satellites by reducing the design-load and vibration-test specifications for on-board components. In this study, a three-axis passive launch-vibration isolation system, based on superelastic shape memory alloy (SMA) technology, was developed to significantly attenuate the dynamic launch loads transmitted to a small satellite. This provides a superior damping characteristic, achieved by superelastic SMA blades stiffened by multilayered thin plates with viscous lamina adhesive layers of acrylic tape. The basic characteristics of the proposed isolation system with various numbers of viscoelastic multilayers were obtained through a static load test. In addition, the effectiveness of the design was validated through a launch environment simulating sine and random vibration tests.

Применение параллелограммного механизма с эффектом квазинулевой жесткости в виброзащитных системах кресла оператора строительно-дорожной машины

For vibration protection of operators of construction and road machines, a promising direction is the use of passive vibration protection systems based on mechanisms with quasi-zero rigidity. Passive vibration isolation systems, being less complex than active ones, require less frequent maintenance, are cheaper to manufacture and more reliable than active ones. The problem of selecting the optimal, most reliable and simple design of the mechanism with the effect of quasi-zero rigidity remains urgent. In this case, the most widespread use of elements that create negative stiffness. This requires elements with positive stiffness in the mechanism, which complicates the design. More promising structures of mechanisms, where elements with negative stiffness are not separated into a separate structure. In mechanisms such as the parallelogram, studied in this work, a section with quasi-zero stiffness can be provided with just one tension spring, which simplifies the design and reduces the cost of the entire vibration protection system. By the method of direct analytical inference for the presented diagram of a parallelogram mechanism with one spring, analytical expressions are obtained for the tensile force of the spring necessary to compensate for the force of gravity of the chair with the operator on the height of the chair and the length of the spring. As an example, the graphical dependences of the spring tensile force on the chair lift and on the spring’s own length are given as an example. It was found that the static force characteristic of the spring is a straight line passing through the origin. That is, the zero force corresponds to the zero spring length, which is not technically feasible. It is proposed to use a mechanism that replaces the tension spring, which will provide a given power characteristic.

Design and Research of Semiactive Quasi-Zero Stiffness Vibration Isolation System for Vehicles

The vehicle-mounted equipment is easy to be disturbed by external vibration excitations during transportation, which is harmful to the measurement accuracy and performance of the equipment. Aiming at the vibration isolation of the vehicle-mounted equipment, a semiactively controlled quasi-zero stiffness (QZS) vibration isolator with positive and negative stiffness is proposed. The vertical spring is paralleled with a magnetorheological (MR) damper, and the semiactive on-off control scheme is adopted to control the vibration. The analytical expression of the isolator’s displacement transmissibility is derived via the averaging method. Then, the vibration isolation performance under different road excitations and different driving speeds is simulated and compared with the uncontrolled passive QZS vibration isolator. In addition, the mechanical structure of the semiactive QZS isolator is designed and manufactured, and the test system is built by LabVIEW software and PXI embedded system. The isolation effect of the semiactive QZS isolator is verified through test data. It is found that the proposed semiactive QZS isolator shows excellent vibration isolation performance under various road excitations, while the passive QZS isolator is effective only under harmonic excitations. The vertical acceleration of vehicle-mounted device can be decreased over 70% after isolation, and the vibration isolation effect is remarkable. The design idea and research results of the semiactive QZS isolator may provide theoretical guidance and engineering reference for vibration isolation.

Vibration error compensation algorithm in the development of laser interference absolute gravimeters

Abstract. Measurement error arising from vibration interference is recognized as the primary obstacle limiting the accuracy and stability of laser interference absolute gravimeters. The present work addresses this issue by proposing a global search optimization algorithm that determines the optimal absolute value of gravity based on the measured time–displacement coordinates of a falling body and the signal obtained from the passive vibration isolation system of the inertial reference corner cube in a laser interference absolute gravimeter. Results of numerical calculations conducted under vibration interference conditions with added white noise resulting in a signal-to-noise ratio of 40 dB demonstrate the following. The accuracy and standard deviation of the gravimeter obtained using the proposed algorithm are −0.04 µGal (1µGal=1×10-8 m s−2) and 0.24 µGal, respectively, while those values obtained by the standard least-squares solution are 10.19 and 154.11 µGal, respectively. The test results indicate that the average response of the reference value of acceleration due to gravity superimposed by a disturbance of 1.00 µGal is 1.01 µGal using the proposed algorithm and 0.87 µGal using the standard least-squares solution.

DYNAMIC PROPERTIES OF POST-BUCKLED SHAPE MEMORY ALLOY AND ITS APPLICATION TO A BASE ISOLATOR FOR VERTICAL VIBRATION

In recent years, high performance and compact vibration isolators have been in demand to support the advancement of precision technology. Among various vibration isolators, a passive vibration isolator is the most commonly adopted form due to its simplicity, stability and low cost. Previously, the authors have proposed a simple and compact passive vibration isolator for the vertical direction using a post-buckled shape memory alloy (SMA) beam. This isolator achieved a low natural frequency assuring high static stiffness by utilizing the negative tangent stiffness of a post-buckled SMA beam. It is expected that the appearance of the negative stiffness is related to the phase transformation of a post-buckled SMA beam, however, the fundamental principle of the appearance and the response for a reciprocating motion (vibration) have not been clarified. In this study, to clarify these characteristics, the restoring force of an SMA beam subjected to reciprocating motion in its post-buckled state was measured experimentally and predicted by Finite Element Analysis in which the phase transformation of the post-buckled SMA was considered. As the result, it was found that the restoring force converged to a certain force when SMA was subjected to reciprocating motion. It was also found that the negative tangent stiffness arose when the phase of SMA transforms from Austenite phase to Martensite phase in compression process. Therefore, SMA with small hysteretic property in the stress-strain curve is appropriate for an effective isolation element. In future research, it will be necessary to validate the performance of the isolator considering the phase transformation.

A brief overview of 8 m prototype facility of laser interferometer for Taiji pathfinder mission

The 8 m laser interferometer prototype facility is currently being constructed at the Institute of Mechanics, Chinese Academy of Sciences in Beijing, China. It aims to perform laser interferometer experiments and pico-meter precision detection and calibration for Taiji pathfinder mission. The seismically isolated ground and passive vibration isolation are interconnected and the optical benches are stabilized by them, which can form two low-noise testbeds inside a 40 m3 ultra-high vacuum system. An on-ground laser interferometer demonstration used for satellite–satellite tracking will be constructed. In this article, the experimental facility and the employed methods will be described, and the technical details of subsystems will be covered in future papers.

Force transmissibility of a 6-DOF passive quasi-zero stiffness vibration isolation platform

Force transmissibility of a 6-DOF passive quasi-zero stiffness vibration isolation platform

Tilt Active Vibration Isolation Using Vertical Pendulum and Piezoelectric Transducer with Parallel Controller

Tilt vibrations inevitably have negative effects on some precise engineering even after applying horizontal and vertical vibration isolations. It is difficult to adopt a traditional passive vibration isolation (PVI) scheme to realize tilt vibration isolation. In this paper, we present and develop a tilt active vibration isolation (AVI) device using a vertical pendulum (VP) tiltmeter and a piezoelectric transducer (PZT). The potential resolution of the VP is dependent on the mechanical thermal noise in the frequency bandwidth of about 0.0265 nrad, which need not be considered because it is far below the ground tilt of the laboratory. The tilt sensitivity of the device in an open-loop mode, investigated experimentally using a voltage controller, is found to be (1.63±0.11)×105 V/rad. To compensate for the hysteresis nonlinearity of the PZT, we experimentally established the multi-loop mathematical model of hysteresis, and designed a parallel controller consisting of both a hysteresis inverse model predictor and a digital proportional–integral–differential (PID) adjuster. Finally, the response of the device working in close-loop mode to the tilt vibration was tested experimentally, and the tilt AVI device showed a good vibration isolation performance, which can remarkably reduce the tilt vibration, for example, from 6.0131 μrad to below 0.0103 μrad.

Bio-inspired toe-like structure for low-frequency vibration isolation

Inspired by the cushioning effect of the felid paws in contact with the ground, a novel bio-inspired toe-like structure (TLS) is developed and systematically studied for low-frequency vibration isolation. The TLS consists of two rods with different length (as phalanxes) and a linear spring (as muscle). Based on Hamiltonian principle, the dynamic model is established considering spring deformation and joint rotation damping. The derived equivalent stiffness reveals that the proposed TLS possesses favorable high static and low dynamic stiffness (HSLDS) characteristics in a wide displacement range. Besides, displacement transmissibility suggests that the proposed TLS isolator has low resonance frequency and can effectively isolate base excitation at low frequencies. Comprehensive parameter analysis shows that the inherent nonlinearities in stiffness and damping is conductive to vibration isolation and can be designed/adjusted on demand by selecting suitable structural parameters. This flexibility gives TLS advantages and great potential in extensive engineering applications when subjected to variable vibration loads. A prototype is fabricated and tested for a comprehensive recognize of its advantageous vibration isolation performance in low frequency band. The vibration with excitation frequency higher than 3 Hz can be effectively isolated. This novel bio-inspired TLS provides a feasible approach to passive vibration control and isolation in low frequency band.

High‐performance vibration isolation technique using passive negative stiffness and semiactive damping

AbstractAmong active, semiactive, and passive vibration isolation methods, active control can provide the best isolation performances. However, high‐energy consumption hinders its wide applications in civil engineering field. This paper proposes a novel vibration isolation technique based on a passive negative stiffness spring (NSS) and a semiactive device (SAD), aiming to achieve an active isolation performance by using a low‐power semiactive technique. Due to its nature of negative potential energy, an NSS enables the semiactive isolation system to provide negative transient power flow that injects power into the structure and avoids the clipping phenomenon of semiactive control forces. Consequently, the combined NSS and SAD isolation system can perfectly generate the theoretical control forces calculated by an active control algorithm and achieve a considerably improved semiactive isolation performance. The prospects and performance advantages of the proposed NSS and SAD isolation system are validated through a series of numerical simulations of single‐degree‐of‐freedom and multi‐degree‐of‐freedom structures excited by various types of ground motions and a benchmark building model excited by seismic ground motions.

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.