Vibration Isolation Table Research Articles

343 低次元システム同定法を用いた除振台の制御系自動最適化(産業機器の運動と振動の制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

343 低次元システム同定法を用いた除振台の制御系自動最適化(産業機器の運動と振動の制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

410 転倒防止装置つきトラック用除振台の研究(制震I,OS-2 耐震・免震・制震,総合テーマ「伝統を,未来へ!」)

Precision instruments and cultural heritages are transported by tracks. It is necessary to prevent the overturning caused by the large acceleration in horizontal direction generated by a sudden braking. It is also important to isolate the vertical vibration caused by road roughness. In this study, the overturning is prevented by installing the mechanism that the table tilts naturally according to the horizontal force. Moreover, vibration in a vertical direction is isolated by using the air spring which is able to change both the static height and the spring constant. The effect of the vibration isolation table with the overturning prevention mechanism is investigated theoretically, and the validity is verified through calculations and experiments.

Focus on vacuum and cryogenics

Focus on vacuum and cryogenics

A new, high precision, quick response pressure regulator for active control of pneumatic vibration isolation tables

Abstract Pressure regulators are important elements in pneumatic systems. Relief-type precision pressure regulators are commonly used to control the supply pressure to actively controlled pneumatic vibration isolators. Herein, a high precision, quick response pneumatic pressure regulator is proposed. This consists of an isothermal chamber, a servo valve, a pressure sensor, a quick response laminar flow sensor (QFS), and a pressure differential sensor (PD sensor) as developed by the authors. Slight changes of pressure in the chamber can be detected by the PD sensor and are fed back to the servo valve to maintain the pressure at a desired value. The performance of this regulator was confirmed experimentally in comparison with one available commercially. The regulator was then applied to the supply pressure regulation of an actively controlled pneumatic vibration isolation table. The superior performance of the regulator is clearly shown in the experimental results, especially in terms of avoiding effects from upstream or downstream disturbances.

Development of high-field STM for 18 T cryocooled superconducting magnet

To study the nanoscale electronic order in strongly correlated electron systems and vortex states in high-Tc superconductors in high magnetic fields, we have developed scanning tunneling microscopy (STM) for the 18 T cryocooled superconducting magnet (18T-CSM). The test results of the STM operation in the 18T-CSM at room temperature indicate that our STM has a good atomic resolution up to 18 T when we use the nonmagnetic vibration-isolation table which reduce the vibration noise from the cryocoolers of the 18T-CSM. In this paper, we report on the design of the high-field STM system for large-scale magnets and its performance.

Performance enhancement of pneumatic vibration isolation tables in low frequency range by time delay control

As environmental vibration requirements on precision equipment become more stringent, the use of pneumatic isolators has become more popular and their performance is subsequently required to be further improved. Dynamic performance of passive pneumatic isolators is related to various design parameters in a complicated manner and that in low-frequency range is limited by resonance frequency or volume of pneumatic chambers in practice. In this study, an active control technique, called as time delay control, is applied to a pneumatic isolator to enhance the isolation performance in the low frequency range where the passive techniques have difficulties. This time delay control technique is taken especially because it is known to be useful for the low frequency control. The procedure of applying the time delay control technique to the pneumatic isolator is presented, together with how to resolve distortion problems in actuator dynamics in implementing the active control technique into a pneumatic system. Effectiveness of the technique in enhancement of transmissibility performance is shown based on simulation as well as experiments. Comparisons with passive pneumatic isolators are also presented.

部分空間法と周波数領域最小二乗近似を用いた除振台の低次元システム同定(機械力学,計測,自動制御)

部分空間法と周波数領域最小二乗近似を用いた除振台の低次元システム同定(機械力学,計測,自動制御)

526 部分空間法と周波数領域最小二乗近似を用いた除振台の低次元システム同定

A system identification technique for a vibration isolation table by using subspace method (N4SID) and Frequency-Domain Least-Squares Approximation (FDLSA) is studied in this paper. The vibration isolation table is supported by four pneumatic actuators at corners of the table. A 3DOF mathematical model of the vibration isolation table is constructed. The regulator for the pneumatic actuator is driven by a stepping motor. A procedure to obtain the minimum-order-model is proposed, and the procedure can be fully automated. Effectiveness of proposed approach is examined by experiments.

Wire-Based Ureteral Stents: Impact on Tensile Strength and Compression

Objectives To evaluate the performance of coil-based ureteral stents in terms of tensile strength and the radial compression force. Methods Three Cook Resonance (RES) metallic coil stents and three coil-reinforced Applied Medical Silhouette (SIL) ureteral stents were tested. An MTS MicroBionix Testing System using Testworks II software, vibration isolation table, and 5-N load cell were used to measure tensile and compressive strength. Stents were placed in hydraulic grips spaced 24 cm apart and stretched at a rate of 5 mm/s for 1 second under uniaxial tension. Extrinsic compression was exerted in 0.2-mm increments to maximum compression. The Young’s modulus, E, was calculated for each trial using the engineering stress. Comparisons were made with the Cook C-flex, which in previous studies was shown to be stiffer and more resistant to compression than other traditional polymer stents. Results The RES and SIL stents demonstrated tensile strengths of 936 ± 485 kPa and 770 ± 82 kPa, respectively ( P = 0.02). The elastic modulus required to cause extrinsic compression was lower for the RES (63,248 ± 3218 Pa) than for the SIL (105,664 ± 11,529 Pa) ( P <0.001). Both stents were more resistant to stent compression than previously tested stents without coil-reinforcement, the strongest of which was the Cook C-Flex (E = 30,355 ± 910 Pa; P <0.001). Conclusions Both the Cook Resonance and Applied Medical Silhouette stents are more resistant to extrinsic stent compression than ureteral stents that are not coil-reinforced. The Cook Resonance has a higher tensile strength, whereas the Applied Medical Silhouette is more resistant to extrinsic compression.

공기스프링을 이용한 방진테이블의 능동 제어

In the process of accurate manufacture and measurement, it is necessarily required to isolate external or internal vibration due to external disturbance and internal actuators. The higher vibration isolation system gets damping around resonance, the better it is generally. This paper analyzes the performance of an existing passive air-spring for vibration isolation table by using experiment and simulation. Optimal design for a passive air spring can be obtained by tuning the size of the orifice. Also design for an active isolation system is carried out by applying PID controller and considering non-linearity of pneumatic characteristics with help of look-up table. We have developed the active vibration isolation table with the better isolation performance.

상판 위 질량의 순간적인 움직임에 의해 가진되는 6-자유도 공압제진대의 진동 응답에 대한 연구

As environmental vibration requirements on precision equipments get more stringent, use of pneumatic vibration isolators becomes more crucial and, hence, their dynamic performance needs to be further improved. Dynamic behavior of those pneumatic vibration Isolation tables is very important to both manufacturer and customer as performance specifications. Together with conventional transmissibility, transient response characteristics are another critical performance index especially when movements of components, e.g., x-y tables, of the precision equipments are very dynamic. In this paper, analysis on transient response of a pneumatic vibration isolation table loaded by a mass moving on it is presented. This is a conventional dynamics problem on a rigid body with 6 degree of freedom and a mass with another degree of freedom. How to obtain transient responses of the isolation table is described when the movements of the mass are prescribed relative to the table.

Active Vibration and Attitude Control of a Vibration Isolation Table with Pneumatic Actuators (A Modeling Method for the Redundant System of Actuators and Sensors)

Active control of a vibration isolation table using pneumatic actuators is studied in this paper. The vibration isolation table is supported by four pneumatic actuators at corners of the square rigid table. A 3DOF physical model of the vibration isolation table is constructed with taking account of redundancy of the actuators and sensors. We introduce a method to determine the air pressure of each actuator to minimize the error between the average pressure of the actuators and the air pressure of each actuator. The regulator for the pneumatic actuator is driven by a stepping motor. Characteristics of the transfer function from input pulse for the stepping motor to the air pressure of the actuator are investigated experimentally and the mathematical model of the actuator is constructed as a second order delay system. Type I digital servo system is applied to control the vibration and position of the vibration isolation table. Control performance of the system is verified experimentally and the results are shown in figures.

117 除振台モデルのスカイフック制御(機械力学)

117 除振台モデルのスカイフック制御(機械力学)

상용 유한요소해석 프로그램을 이용한 공압 스프링 내 다이아프램의 복소강성 산출

An accurate mathematical model for complex stiffness of the pneumatic spring would be necessary for an efficient design of a pneumatic spring used in vibration isolation tables for precision instruments such as optical devices or nano-scale equipments. A diaphragm, often employed for prevention of air leakage, plays a significant role of complex stiffness element as well as the pressurized air itself Therefore, effects of the diaphragm need to be included in the dynamic model for a more faithful description of dynamic behavior of pneumatic spring. But the complex stiffness of diaphragm is difficult to predict In an analytical way, since it is a rubber membrane of complicated shape in itself. Moreover, the diaphragm should be expandable in response to pressurization inside a chamber, which makes direct measurement of complex stiffness of diaphragm extremely difficult. In our earlier research, the complex stiffness of diaphragm was indirectly measured, which was just to eliminate the theoretical stiffness of pressurized air from the measured complex stiffness of the pneumatic spring. In order to reflect complex stiffness of inflated diaphragm on the total stiffness at the initial design or design improvement stage, however. it is required to be able to predict beforehand. In this paper, how to predict the complex stiffness of inflated rubber diaphragm by commercial FE codes (e.g. ABAQUS) will be discussed and the results will be compared with the indirectly measured values.

In vitro evaluation of ureteral stent compression

Objectives To evaluate the force required to radially compress ureteral stents and the impact of compression on stent performance across a broad range of stent sizes and manufacturers. Methods Fourteen ureteral stents ranging in size from 6F to 10.3F were evaluated for radial compression using an MTS Micro Bionix Testing System using Testworks II software, 5N load cell, vibration isolation table, and socket set screws with rounded caps. Radial compression was exerted in 0.2-mm increments. Cycles of compression and a 100-second hold time were repeated for each stent to maximal compression. Three trials were completed for each stent. The Young’s Modulus, E, was calculated from each trial using the engineering stress. Simultaneous flow data using normal saline were collected for the Amplatz stent. Results The Cook C-Flex (E = 30,355 ± 910 Pa), Microvasive Percuflex Plus 6F (E = 28,973 ± 250 Pa), Cook EndoSof (E = 28,403 ± 471 Pa), and Fossa Open Lumen (E = 28,627 ± 5,338) were the most resistant to compression and the Cook Amplatz 10.2F (E = 11,922 ± 220 Pa) and Microvasive Percuflex Plus 10.3F (E = 8,247 ± 286 Pa) were the least resistant to compression. Stress relaxation occurred similarly in all stents. Flow through the Cook Amplatz stent decreased at a rate of 5 mL/s/mm of compression linearly (R 2 = 0.95). Conclusions Stents resistant to radial compression are critical for function in the face of extrinsic ureteral obstruction. The Cook C-Flex ureteral stent resisted extrinsic compressive forces best. Although large-lumen stents are often used in this clinical situation, they were the most susceptible to compressive forces.

502 モータ駆動空気圧レギュレータを用いた除振台の冗長自由度を考慮したアクティブ制御

本研究では,ベローズ型空気ばねによって支持される除振台を対象とし,ステッピングモータで駆動されるレギュレータのバルブを高速・高精度に開閉することにより空気圧をアクティブ制御し,振動の抑制とともに除振台の高精度な位置決めを目標とする.物理モデルの構築には,アクチュエータの数が冗長となることを考慮して,各アクチュエータの発生力を決定する手法を提案する.制御系は最適I型デジタルサーボ系を構成し,数値計算と実験を実施して制御性能を確認する.テーブルは剛体とし,テーブルの重心を原点とした座標系を設定する.3自由度振動系の運動方程式は MX+DX+KX=F^* (A1)と表すことができる.ただし, F^*=[F^* M^*_x M^*_y]^T (A2) であり,F^*は重心に作用するz軸方向の力,M^*_xおよびM^*_yはそれぞれx軸およびy軸まわりのモーメントである.座標(x_i,y_i)に配置された第iアクチュエータが発生すべき力f_iは,各アクチュエータが発生する力と各アクチュエータ発生力の平均値との間の誤差を評価に組込んだ評価関数 J=1/2α_x(M_x-M^*_x)^2+1/2α_y(M_y-M^*_y)^2+1/2α_F(F-F^*)^2+1/2α_ΔΣ^^N__<j=1>(f_j-F/N)^2 (A3)を用いて最小二乗法によって次のように求めることができる. f=[f_1 … f_n]^T=G^<-1>_1G_2W_αF^*=WF^* (A4) 最適I型デジタルサーボ系を構成し,鉛直方向の目標位置を1mm上昇させた場合の時刻歴応答を図A1に示す.テーブル中央の鉛直方向変位は約3秒で目標に到達し,十分な目標追従性能が得られている.

A multipole array magnetic spring

This paper presents research on a magnetic spring concept, which has application to the development of a vibration isolation table. Features of the design are scalable, noncontact load bearing and a single degree of instability.

Combined molecular beam epitaxy low temperature scanning tunneling microscopy system: Enabling atomic scale characterization of semiconductor surfaces and interfaces

A molecular beam epitaxy and low temperature scanning tunneling microscopy chamber have been integrated to characterize both compound and elemental semiconductor surfaces and interfaces. The integration of these two commercially available systems has been achieved using a custom designed sample transfer mechanism. The MBE growth chamber is equipped with electron diffraction and provides substrate temperature measurements and control by means of band-edge thermometry accurate to within ±0.5°C. In addition, the microscope can operate at temperatures as low as 4K and perform ballistic electron emission microscopy measurements. The chamber that houses the microscope includes a preparation chamber with an evaporation source for metals. The entire STM chamber also rests on an active vibration isolation table, while still maintaining an all ultrahigh vacuum connection to the MBE system.

3406 三次元防振・免震テーブルの開発研究(OS16 製造現場と設計・システムII)

In this paper, a three-dimensional vibration isolation table using semicircular arc springs, which is a seismic isolation table for horizontal directions and a vibration isolation table for vertical direction, and a vertical seismic isolation table using a rack and pinions were developed. The trial vibration isolation tables were made and their effects of vibration isolation were discussed experimentally and numerically.

511 空気アクチュエータを用いた除振台モデルの特性解析とアクティブ制御(機械力学・振動)

511 空気アクチュエータを用いた除振台モデルの特性解析とアクティブ制御(機械力学・振動)