Vibration Isolation Table Research Articles

Dynamic quantitative phase imaging using calcite crystal-based temporally stable interferometer

This paper describes the development of a common path off-axis quantitative phase microscope (QPM), enabling high-speed quantitative measurements of sub-cellular dynamics in a live cell. The proposed 4f optical system consists of a polarizer, lenses, calcite crystal, pinhole and analyser, attached to the output port of an optical microscope converting it into a temporally stable QPM. The temporal phase stability of this optical configuration is measured to be equal to ∼20 mrad without a vibration isolation table. The utility of the microscope is demonstrated by conducting experiments on a polystyrene sphere (dia. 12 μm) and human red blood cells (RBCs). Furthermore, the developed system is implemented to study temporal membrane fluctuation in human RBCs over ∼30s and mouse embryonic fibroblast cell dynamics over 2 hours. Therefore, the system offers an energy-efficient and simple solution for generating object and reference beams for common-path QPM, making it an attractive alternative to existing approaches.

Dynamic Research on Low-frequency Vibration Isolation Tables

In the paper, an establishment of dynamic characteristics of tabletops of the newly-developed optical tables is being discussed upon. Low-frequency vibration isolation systems are reviewed. Theoretical and experimental tests have been performed. Dynamic models of an optical table on a vibrating platform at different excitations have been developed, the dynamic displacement and the resonance frequencies of the system have been established and vibration transmissibility curves have been presented. The obtained dynamic characteristics of the mechanical passive low-frequency vibration isolation system show that such a system is able to isolate the vibrations effectively. The results of the performed experimental tests confirm the data of the theoretical research.

Study on the Compressive Properties of an Elastomeric Porous Cylinder Using 360° Three-Dimensional Digital Image Correlation System.

To study the compressive properties of an elastomeric porous cylinder, a 360° 3D digital image correlation (DIC) system is proposed. This compact vibration isolation table system captures different segments of the object from four different angles and fields of view, enabling a comprehensive measurement of the full surface of the object. To increase the stitching quality, a coarse-fine coordinate matching method is presented. First, a three-dimensional rigid body calibration auxiliary block is employed to track motion trajectory, which enables preliminary matching of four 3D DIC sub-systems. Subsequently, scattered speckle information characteristics guide fine matching. The accuracy of the 360° 3D DIC system is verified through a three-dimensional shape measurement conducted on a cylindrical shell, and the maximum relative error of the shell's diameter is 0.52%. A thorough investigation of the 3D compressive displacements and strains exerted on the full surface of an elastomeric porous cylinder are investigated. The results demonstrate the robustness of the proposed 360° measuring system on calculating images with voids and indicate a negative Poisson's ratio of periodically cylindrical porous structures.

Design and Implementation of an Active Vibration Control Algorithm Using Servo Actuator Control Installed in Series with a Spring-Damper

The membrane-type air spring can be used to suppress lateral vibration of a vibration isolation table. However, compared to voice coil actuators, pneumatic actuators are difficult to use for precise vibration control, because servo valves have nonlinear dynamic characteristics. Therefore, actuators, such as voice coil actuators, can be placed in parallel with air springs, allowing force-type actuators to provide additional force to the system. These actuators generate force. In the case of a ball-screw mechanism device or a linear servomotor, it is an actuator that generates displacement. These actuators are represented as serial active systems. Serial active systems are structurally simpler than parallel active systems. However, there are very few studies on vibration isolation systems using serial active systems compared to parallel active systems. As the two are different types of systems, a new control algorithm suitable for the serial active system is needed. This study proposes a system in which an actuator capable of accurately controlling displacement is connected in series with a support spring-damper. A new active vibration control algorithm for the proposed control system is also developed, which is termed the position input and position output. The proposed control algorithm uses the displacement of the system as an input and outputs the desired displacement of the actuator installed in series with the damper and spring. The proposed control algorithm increases the damping at the target frequency and reduces the response of the system. Numerical studies and experiments were conducted on the single-degree-of-freedom and multi-degree-of-freedom systems. The results show the efficacy of the proposed control system and the novel control algorithm for the vibration suppression of the lateral vibration of a vibration isolation table.

Construction of a vector-field cryogenic magnetic force microscope.

Owing to the high resolution of magnetic force microscopes (MFMs) operating at low temperatures and high-applied magnetic fields, they can be employed to study various phenomena observed in topological magnetic materials and superconductors. In this study, we constructed a low-temperature MFM equipped with a 2-2-9-T vector magnet and a three-axis fiber-optic alignment system. The three-axis alignment device enables in situ calibration of the scanner at low temperatures as well as optimizes the intensity and sensitivity of the interferometer signal. A massive homebuilt vibration isolation table lowers the resonance frequency of the system and minimizes mechanical noise. Consequently, the minimum detectable force gradient of our proposed model is close to the thermodynamic limit of the cantilever. To demonstrate the low-temperature capability of the MFM, we obtained magnetic domain images of the van der Waals ferromagnet Fe4GeTe2 and the Abrikosov superconducting vortices of an Nb film. Furthermore, we performed field angle-dependent MFM experiments in a van der Waals magnetic insulator Cr2Ge2Te6 to verify its vector-field functionality and observed a transition in the domains from the stripe to the bubble phase with respect to the magnetic field angle. The vector-field capability of our MFM can be useful for investigating various anisotropic magnetic phenomena in topological magnetic and superconducting materials.

Development of a near-5-Kelvin, cryogen-free, pulse-tube refrigerator-based scanning probe microscope.

We report the design and performance of a cryogen-free, pulse-tube refrigerator (PTR)-based scanning probe microscopy (SPM) system capable of operating at a base temperature of near 5 K. We achieve this by combining a home-made interface design between the PTR cold head and the SPM head, with an automatic gas-handling system. The interface design isolates the PTR vibrations by a combination of polytetrafluoroethylene and stainless-steel bellows and by placing the SPM head on a passive vibration isolation table via two cold stages that are connected to thermal radiation shields using copper heat links. The gas-handling system regulates the helium heat-exchange gas pressures, facilitating both the cooldown to and maintenance of the base temperature. We discuss the effects of each component using measured vibration, current-noise, temperature, and pressure data. We demonstrate that our SPM system performance is comparable to known liquid-helium-based systems with the measurements of the superconducting gap spectrum of Pb, atomic-resolution scanning tunneling microscopy image and quasiparticle interference pattern of Au(111) surface, and non-contact atomic force microscopy image of NaCl(100) surface. Without the need for cryogen refills, the present SPM system enables uninterrupted low-temperature measurements.

Noninteracting Control Design for 6-DoF Active Vibration Isolation Table with LMI Approach

This paper proposes a novel control strategy for six degrees-of-freedom active vibration isolation tables. In these systems, the most challenging issue is to suppress the external vibrations and isolate the internal interactions while still preserving the system’s robustness when facing uncertainties. A noninteracting controller is designed to tackle these problems. The resulting control system is completely decoupled in the sense that each system output is independently controlled to follow the corresponding reference signal. In this paper, the model of an active vibration isolation table is firstly derived. Conditions for system stability and decoupled performance are then discussed. The control law is formulated using the linear matrix inequality approach, which results in optimal control gains for the control objectives. With the proposed controller, complex system characteristics can be handled more efficiently such that an effective system is designed to obtain good control performance. Finally, simulations and comparison studies were conducted, and the results validate the efficiency of the proposed scheme.

Active Fault Diagnosis Design for Redundantly Driven Active Vibration Isolation Tables

Active Fault Diagnosis Design for Redundantly Driven Active Vibration Isolation Tables

Highly temporal stable, wavelength-independent, and scalable field-of-view common-path quantitative phase microscope.

.Significance: High temporal stability, wavelength independency, and scalable field of view (FOV) are the primary requirements of a quantitative phase microscopy (QPM) system. The high temporal stability of the system provides accurate measurement of minute membrane fluctuations of the biological cells that can be an indicator of disease diagnosis.Aim: The main aim of this work is to develop a high temporal stable technique that can accurately quantify the cell’s dynamics such as membrane fluctuations of human erythrocytes. Further, the technique should be capable of acquiring scalable FOV and resolution at multiple wavelengths to make it viable for various biological applications.Approach: We developed a single-element nearly common path, wavelength-independent, and scalable resolution/FOV QPM system to obtain temporally stable holograms/interferograms of the biological specimens.Results: With the proposed system, the temporal stability is obtained without using any vibration isolation table. The capability of the proposed system is first demonstrated on USAF resolution chart and polystyrene spheres ( diameter). Further, the system is implemented for single shot, wavelength-independent quantitative phase imaging of human red blood cells (RBCs) with scalable resolution using color CCD camera. The membrane fluctuation of healthy human RBCs is also measured and was found to be around 47 nm.Conclusions: Contrary to its optical counterparts, the present system offers an energy efficient, cost effective, and simple way of generating object and reference beam for the development of common-path QPM. The present system provides the flexibility to the user to acquire multi-wavelength quantitative phase images at scalable FOV and resolution.

Robust frequency stabilization and linewidth narrowing of a laser with large intermittent frequency jumps using an optical cavity and an atomic beam.

An experimental method is developed for robust frequency stabilization using a high-finesse cavity when the laser exhibits large intermittent frequency jumps. This is accomplished by applying an additional slow feedback signal from Doppler-free fluorescence spectroscopy in an atomic beam with increased frequency locking range. As a result, a stable and narrow-linewidth 556 nm laser maintains the frequency lock status for more than a week and contributes to more accurate evaluation of the Yb optical lattice clock. In addition, the reference optical cavity is supported at vibration-insensitive points without any vibration isolation table, making the laser setup more simple and compact.

Surface Profile Measurement and Error Compensation of Triangular Microstructures Employing a Stylus Scanning System

Microstructure-based function components are widely used in precision engineering. Surface profile measurement is an essential tool to verify the manufacturing quality of microstructures and to enhance the working performance of the device employing microstructures as function components. However, highly accurate surface profile measurements are difficult to perform for microstructures owing to their complex surface topographies. In this paper, a measurement system is proposed for the surface profile measurement of microstructures. The main components of the measurement system are a precision displacement stage to move the workpiece, a homemade probing system with a diamond microstylus to sense the surface profile variation of the microstructures on the workpiece, and a vibration isolation table to reduce the disturbance of the measurement environment. In addition, the stability of the measurement was experimentally investigated. Microstructures with shape of equilateral right triangle were employed as the measurement specimen, and the surface profile of triangular microstructures was measured by employing two methods to correct errors caused by the specimen inclination and the radius of the stylus tip. The shape, depth, and period of the measured microstructures were also detected based on the results of the surface profile measurement. Experimental results demonstrate the feasibility of the proposed surface profile measurement for microstructures with complex surface topographies.

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are sufficiently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.

Design and control of active vibration isolation system with an active dynamic vibration absorber operating as accelerometer

This paper exhibits the development of a vibration isolation system using an active dynamic vibration absorber (ADVA) as an accelerometer in a low-frequency range; whereas, it operates as a vibration control device in a high-frequency range. The control signal of the ADVA gives an information of the low-frequency acceleration. At the same time, in the active vibration isolation system, an air spring is employed as a low-frequency control device and an inexpensive MEMS-type accelerometer is used to measure the acceleration of the vibration in a high-frequency range. The sensor fusion technique is applied to integrate the output of the MEMS-type accelerometer and the acceleration estimated from the ADVA. The motions of the vibration isolation table and the absorber mass of the ADVA are controlled by PID control. The integrated acceleration by the sensor fusion is transmitted through a low-pass filter to the air spring and through a high-pass filter into the ADVA to attain additional acceleration and velocity feedback to the PID controls. Several experimentations and observations are conducted to measure the transmissibility and compliance. The experimental and simulation results demonstrate that the performance and operative precision of the developed active vibration isolation system are improved by the additional absolute acceleration and velocity feedbacks in terms of compliance as well as transmissibility characteristics.

Design and testing of a compact non-orthogonal two-axis Lloyd's mirror interferometer for fabrication of large-area two-dimensional scale gratings

A compact and stable two-axis Lloyd’s mirror interferometer based on a new non-orthogonal type of mirror-substrate assembly is designed for fabrication of 100 mm × 100 mm large-area two-dimensional (2D) diffraction scale gratings in a research laboratory or a small-scale manufacturing facility. At first, the required mirror sizes used in the new non-orthogonal type and the conventional orthogonal type are compared based on geometrical analysis. It is identified that the width of the mirror can be reduced to half in the non-orthogonal type while the required mirror height and the expanded laser beam diameter are comparable to those in the orthogonal type. The shorter mirror width makes it possible to design a compact mirror-substrate assembly so that the overall interferometer can be realized in an overall size of 1480 mm × 730 mm for mounting on a commercially available general-purpose 1500 mm × 1000 mm vibration isolation table for use in research laboratories. It is then verified by simulation that the selected laser source and the designed beam expansion assembly, which are the other main parts of the interferometer, are effective for fabricating the designed grating structures. Experiments are also carried out to demonstrate the feasibility of the constructed interferometer for fabricating 100 mm × 100 mm 2D scale gratings with a short period of 1 μm.

Stability improvement for coil position locking of joule balance

The relative vertical position locking precision between the exciting and suspended coils is an important uncertainty for the Planck constant traceability in joule balance. In order to improve the relative vertical position locking precision, several stability experiments are conducted. The stability characteristics of the suspended and exciting coils are measured using a six-axis laser interferometer system; meanwhile, the effectiveness of the active vibration isolation table is measured using a vibration measurement sensor. The piezoelectric ceramic actuators with PID controller are used to compensate the relative vertical displacement drifts while a six-axis laser interferometer system is used to measure the positions of two coils. Experimental results show that the relative vertical position is stably locked.

Analysis of a vibration isolation table comprising post-buckled Γ-shaped beam isolators

In this paper, the static and dynamic characteristics of a nonlinear passive vibration isolation table is investigated through finite element analysis. The intended application is specifically isolation in the vertical direction where the isolator is required to be sufficiently stiff statically to bear the weight of the isolated object and soft dynamically for small oscillations about its equilibrium position. The modelled configuration consists of a rigid isolation table mounted on two Γ-shaped beam isolators which are loaded to their post-buckled state in their unstable buckling mode by the weight of the isolated mass. A nonlinear static analysis is presented to establish the negative stiffness provided by the buckled beams, and two linear springs are then added in parallel which are chosen to have just sufficient stiffness to restore stability. Modal analysis of the linearized system about its statically deformed position (1mm) gives a natural frequency of just 1Hz which is considerably lower than is achievable by a linear isolator. Motion transmissibility of the linearized system shows a non-resonant isolation region spanning two decades when the system is perfectly symmetric but additional resonance peaks appear when asymmetries are included in either the mass or stiffness distribution. Several strategies are explored for reducing the prominence of these resonances.

G1001004 コイルばねとフリーベアを用いた小型簡易免振テーブル

The authors propose a small isolation table with coil springs and roller bearings in order to obtain a vibration isolation table which is simple in construction, low cost and effects of seismic isolation. The table board is supported by four legs with roller bearings, and connected by four coil springs to the base plate. The table is able to move smoothly any horizontal direction. A sliding type friction damper is also installed beside the legs for suppress the resonance of the isolation table under strong long period components. The trial isolation table is manufactured, and resisting force characteristics are measured. Next, seismic vibration tests are carried out using a shaking table. Response acceleration and displacement are measured when earthquake which has a strong long period component are inputted, and the experimental results are compared with the calculated results. Finally, the effect of seismic isolation and the propriety of the calculation are confirmed.

Self-identification method of arrangement and effective pressure areas for a vibration-isolation table supported with a redundant number of pneumatic actuators

Self-identification method of arrangement and effective pressure areas for a vibration-isolation table supported with a redundant number of pneumatic actuators

G1000204 冗長支持空気圧アクティブ除振台のスケーラビリティー獲得と長時間連続稼働の実現法

G1000204 冗長支持空気圧アクティブ除振台のスケーラビリティー獲得と長時間連続稼働の実現法

Generic vibration criteria–based dual-chamber pneumatic spring vibration isolation table design

Dual-chamber pneumatic spring vibration isolation tables are commonly used as the base of precision equipment to isolate vibrations from the floor. During the design of dual-chamber pneumatic spring vibration isolation table, transmissibility is often taken as the performance measure, which does not represent the precision requirements directly and could not be adapted to different floor vibration conditions. In this article, a new performance measure is developed to obtain an optimum isolation performance during the design of a dual-chamber pneumatic spring vibration isolation table. Based on the generic vibration criteria, the weighted root-mean-square velocity of platform vibration in one-third octave bands resulting from the floor excitations is used as the new measure. The platform vibration is predicted by establishing a model of dual-chamber pneumatic spring vibration isolation table, which consists of a platform and four dual-chamber pneumatic springs. The model disturbance inputs are actual random floor excitations (7.98 µm/s, vibration criteria-C level), which are obtained by vibration acquisition test in a typical laboratory. The genetic algorithm is applied to solve this nonlinear optimization problem. The maximum weighted root-mean-square velocity of platform with the optimum design isolation table decreases to 2.35 µm/s, which provides a vibration criteria-E level environment.