Precision Displacement Sensor Research Articles

Design and implementation of a measuring system used to evaluate the mechanical performance of the bone fixators

PurposeThis measuring system is designed to effectively simulate the mechanical reliability of the operated bone fixators. It can be used to pre-evaluate the mechanical performance of the operated fixator on the patients, including the static mechanical properties and fatigue properties when the patient walks after the operation.Design/methodology/approachIt is mainly composed of a one-dimensional platform, a force sensor, a high measuring precision displacement sensor and a servo motor. Loading (which is used to simulate the loading status of the fixators after the operation) of the system is realized by the rotation of the servo motor. It can be read by a high precision force sensor. The relative displacement of the broken bone is obtained by a high precision laser displacement sensor. Corresponding theoretical analysis is also carried out.FindingsCalibrated results of the system indicate that the output voltage and the measured force of the force sensors possess an excellent linear relationship, and the calculated nonlinear error is just 0.0002%. The maximum relative displacement between the operated broken bone under 700 N axial force is about 1 mm. Fatigue test under 550 N loading for 85,000 cycles also indicates the feasibility of the design.Originality/valueThis device is successfully designed and fabricated to pre-evaluate the mechanical performance of the bone fixators. High precision force sensor and displacement sensor are used to successfully increase the measuring ability of the system. This will offer some help to pertinent researchers.

Nano-Displacement Measurement System Using a Modified Orbital Angular Momentum Interferometer

In this study, a nano-displacement measurement system is proposed and demonstrated both theoretically and experimentally, which was based on a modified Mach-Zehnder (M-Z) interferometer using two conjugated orbital angular momentum (OAM) beams. In contrast to the previous M-Z-based OAM interferometer, a reflection module is inserted into the reference arm instead of a simple mirror. As a result, the effect of the transverse position-dependence phase-shift caused by the dove prism can be clearly eliminated and a stable and robust (off-axis insensitive) petal-like interference pattern can be obtained successfully. More importantly, a significant rotation angle of the petal-like pattern vs. the tiny displacement of the tested object can be clearly observed. In accordance with the modified measurement setup, a novel phase-demodulation method enabling to quickly and accurately characterize the rotation angle of the petal-like interference-patterns is proposed and demonstrated also. A tiny displacement ranging from 50 to 800 nm with resolution of <inline-formula> <tex-math notation="LaTeX">$\sim 50$ </tex-math></inline-formula> pm has been measured successfully. The proposed approach may find applications in not only the ultra-high precision displacement sensor, but also the temperature, strain, and refractive index sensors.

Measurement of the Newtonian constant of gravitation G by precision displacement sensors

The Newtonian constant of gravitation G historically has the largest relative uncertainty over all other fundamental constants with some discrepancies in values between different measurements. We propose a new scheme to measure G by detecting the position of a test mass in a precision displacement sensor induced by a force modulation from periodically rotating source masses. To seek different kinds of experimental setups, laser interferometers for the gravitational wave detection and optically-levitated microspheres are analyzed. The high sensitivity of the gravitational wave detectors to the displacement is advantageous to have a high signal-to-noise ratio of 10−6 with a few hours of the measurement time, whereas the tunability of parameters in optically-levitated microspheres can enable competitive measurements with a smaller scale setup dedicated to the G measurement. To achieve an accuracy of G better than currently available measurements, developments in force calibration is essential. These measurements can provide an alternative method to measure G precisely, potentially leading to the improvement in the accuracy of G, as well as a better search for non-Newtonian gravity at a length scale of ∼1 m.

Search for kilogram-scale dark matter with precision displacement sensors

The search for dark matter has been performed mainly for weakly interacting massive particles and massive compact halo objects, and the intermediate mass region has not been investigated experimentally. A method to search dark matter with precision displacement sensors is suggested for this mass range. The search is performed by detecting a characteristic motion of a test mass when it is attracted by a dark matter particle through gravity. Two different types of displacement sensors are examined: optically levitated microspheres and laser interferometers for gravitational wave detection. The state-of-the-art detectors' sensitivity is several orders of magnitude lower to put constraints on dark matter particles. Among the two types of detectors, gravitational wave detectors have higher sensitivities, and a sensitivity 10 times more than the next generation detector can potentially address the existence of dark matter particles of a few kilograms.

Development of Under–anchorage Effective Prestress Detecting Instrument and Engineering Application

For detecting under–anchorage effective prestress of steel strand by lift–off test convenient. Revealing the testing principle of lift–off text and developing the testing in strument. The instrument consists of data acquisition card, oil pressure sensor, high precision displacement sensor and electric oil pump. Based on the graphical software platform LabVIEW, the test program is compiled by using G language. And further gives the program source code. Integrating the texting instrument (LTF 1.0) of under–anchorage effective prestress based on the software and hardware. So the engineering application is carried out. The research results show that the instrument can detect the under-anchorage effective prestress effectively by the load–displacement curve. Meanwhile it has the advantages of high precision, good safety and convenient operation. Through field application, the effective prestress of prestressed steel strand anchor was increased from 54.4% to 94.7%, and same strand dispersion was reduced from 10.2% to 1.7%.

LC공진소자를 이용한 변위센서

In this study, the LC resonators were fabricated with ferrite cores and external capacitors, and then their characteristics were investigated for the purpose of developing new displacement sensor. The frequency dependence of impedance of single resonator was estimated. There were two resonance peaks on the impedance spectrum; one by self inductance and the other by mutual inductance. The resonance frequency was shifted linearly in direct proportion to displacement of the resonator showing the proposed device, a pair of LC resonators, could be used a precision displacement sensor.

Design and Simulation Analysis of Two-Phase Grating-Type Displacement Sensors with Unequal-Pitch

With the development of grating displacement sensors towards higher precision and higher speed of dynamic responses, the traditional design structure is hard to solve the processing difficulty of the increasing number of poles for time grating sensors. In order to realize the analysis on the internal magnetic field distribution of high precision displacement sensor, the unequal pitch grating displacement sensor with two phase model is established using Ansoft Maxwell simulation environment. The feasibility of the two unequal pitch grating displacement sensor and magnetic field simulation are performed based on the proposed sensor model. In addition the detailed synthetic method is proposed for the simulation data. The analysis show the feasibility of the unequal pitch grating displacement sensor with two phase. The proposed displacement sensor decreases the difficulties of machining process technology and increase the pole number. As the result, the measuring precision is improved.

Low transmittance ICF capsule geometric parameters measurement using laser differential confocal technique

A new high precision non-contact measurement using laser differential confocal microscopy is proposed for the outer diameter, inner diameter and wall thickness of the inertial confinement fusion (ICF) capsules. Based on the property of an axial intensity curve that the absolute zero precisely corresponds to the focus of the objective in a laser differential confocal system (LDCS), the approach proposed uses the absolute zero of LDCS axial intensity curve to precisely identify the position of the test point on the outer surface, inner surface and spherical center of ICF capsule in sequence, and uses the high precision displacement sensor to record the position parameter, and thereby achieving the high-precision measurement of the outer diameter, inner diameter and wall thickness of ICF capsule by combining with ray tracing. Theoretical analyses and experiments indicate that the approach has higher resolution, measurement accuracy and measurement efficiency compared with the existing measurement methods.

Cr-N Strain-Gauge-Type Precision Displacement Sensor for Measuring Positions of Micro Stage

A strain-gauge-type precision displacement sensor, which is developed for a usage of micro-XY stage, is described in this paper. A thin-film strain-gauge element, which is made by Cr-N alloy, is directly fabricated on the base of the strain gauge. The direct fabrication and using the Cr-N element are expected to achieve higher sensitivity for displacement detection and better stability against the change of ambient temperature. In this study, several designs of the thin-film strain gauge, including both of two-gauge-type and four-gauge-type, are prepared to compare sensor performances such as sensitivity, stability and so on. The designed patterns of the strain-gauge element are directly fabricated on zirconia plates by using photolithography processes. The fabricated strain gauges are then evaluated as precision displacement sensors. At first, stability of the fabricated Cr-N strain-gauge-type displacement sensor was confirmed by comparing with the one made by a conventional strain gauge. Resolution of the fabricated Cr-N strain-gauge-type displacement sensors was then evaluated by comparing with a commercially-available laser displacement sensor, while giving sub-micrometer-order deformation to the strain-gauge-type displacement sensor. Details of the design, fabrication and evaluation results of the Cr-N strain-gauge-type displacement sensor are described.

Non-Contact Translation-Rotation Sensor Using Combined Effects of Magnetostriction and Piezoelectricity

Precise displacement sensors are an important topic in precision engineering. At present, this type of sensors typically have a single feature of either translation or rotation measurement. They are also inconvenient to integrate with the host devices. In this report we propose a new kind of sensor that enables both translation and rotation measurement by using the combined effect of magnetostriction and piezoelectricity. As a proof of concept, we experimentally realized a prototype of non-contact translation-rotation precise sensor. In the current research stage, through both theoretical and experimental study, the non-contact displacement sensor is shown to be feasible for measuring both translation and rotation either in coarse or fine measurement. Moreover, owing to its compact, rigid structure and fewer components, it can be easily embedded in host equipment.

One Test System Design of Static Stiffness for Machine Tools

Computer is regarded as a center of signal detection, data processing and control in this system, accompanied by precision displacement sensors, pressure sensors and stepper motors and drives. Realize the transition of analog to digital with A/D converter board by VB6.0, and load simulation device steady and uniform by stepper motor, at the same time realize the functions of data calculation processing, storage, querying and sample curve drawing. The experimental results shows that the system has the advantages of a high degree of automation, high test efficiency, high precision, high reliability, stability test performance.

191 マイクロステージ用変位センサに関する研究(機械力学・計測制御I,一般講演)

191 マイクロステージ用変位センサに関する研究(機械力学・計測制御I,一般講演)

A Cadaveric Study of Strain on the Subscapularis Muscle

Muraki T, Aoki M, Uchiyama E, Takasaki H, Murakami G, Miyamoto S. A cadaveric study of strain on the subscapularis muscle. Objectives To measure the strain on 3 fiber groups of the subscapularis muscle at various glenohumeral joint positions and to determine the appropriate shoulder position for subscapularis muscle stretching. Design Repeated-measures design. Setting Biomechanics laboratory. Specimens Nine frozen-thawed glenohumeral joints obtained from 9 fresh cadavers. Interventions Not applicable. Main Outcome Measure The strain on the upper, middle, and lower fiber groups of the subscapularis were measured by precise displacement sensors during 14 different glenohumeral joint positions. Results The glenohumeral joint position that showed the largest strain varied among the 3 fiber groups. Although no position showed significantly large strain on the upper and middle fiber groups, external rotation at 30°, 60°, and 90° of elevation, abduction, flexion, and horizontal abduction revealed significantly greater strain on the lower fiber groups ( P<.005). Additionally, except for external rotation at 0° of elevation, the strain on the lower fiber group was significantly greater than that on the upper and middle fiber groups in external rotation ( P<.005). Conclusions The stretching position of each fiber group of the subscapularis differs depending on the glenohumeral joint position. External rotation at 30° to 60° of glenohumeral elevation, abduction, flexion, and horizontal abduction can significantly stretch the lower fiber group of the subscapularis muscle.

The effect of arm position on stretching of the supraspinatus, infraspinatus, and posterior portion of deltoid muscles: A cadaveric study

The stretching of the supraspinatus and infraspinatus muscles is important to prevent shoulder injuries. Although several authors have advocated various stretching techniques, a general opinion has not been reached owing to the lack of quantitative analysis. Nine fresh cadaveric shoulders were used to measure the strain on the supraspinatus, the middle and inferior portions of the infraspinatus, and the posterior portion of the deltoid muscles during eleven arm positions. The strain on the muscles was measured by precise displacement sensors attached to the center of each muscle belly. In case of the supraspinatus muscle, abduction at extension showed significantly larger strain than that in the neutral position (P < 0.05). Internal rotation at extension showed significantly larger strain in the middle portions of the infraspinatus (P < 0.05). Internal rotation at 30 degrees and 60 degrees elevation as well as extension showed significantly larger strain in the inferior portion of the infraspinatus (P<0.05). Adduction at 60 degrees elevation did not show large strain in the infraspinatus muscle; however, significantly larger strain was observed in the posterior portion of the deltoid muscle. Shoulder stretching techniques that are based on these experimental data can enhance the selective stretching of the corresponding muscles. Application of these techniques is considered to be useful for the prevention and treatment of shoulder injuries.

高精度磁気軸受の研究 (第3報)

The accuracy of ordinary magnetic bearings is not high enough because displacement sensors used for feed-back are inaccurate. The aim of the paper is to clarify limitations of the positioning accuracy of an object of an electromagnetic levitation system in which a flux density sensor and a current sensor are used for estimat-ing the displacement of the object. First, a displacement estimation method using flux density and current signals in an electromagnet is discussed. Then a non-contact positioning system controlled by electromag-nets, Hall elements and current sensors is introduced. The system is provisionally positioned with a precision displacement sensor. Comparison of the resolution, frequency characteristics and measurement range is made between the estimated displacement and the output of the precision sensor to evaluate the accuracy of the estimation. After that, the object is controlled using the estimated displacement as the feedback signal and the accuracy and stability of the estimated displacement are examined. The experimental results show that the resolutions of estimated displacement and positioning were 0.25 μm, the positioning range was more than ± 100 μm, and the stability of positioning due to the ambient temperature variation was 3.0 μm/°C.

Development of a Traceable Laser-Based Displacement Calibration System with Nanometer Accuracy

High precision sensors become increasingly sensitive due to the use of advanced measuring principles and construction techniques. Traceable accuracy though can only be achieved via calibration. Based on a Fabry-Perot interferometer we have developed a calibration set-up for high precision displacement sensors that allows calibrations over a range of 300 μm with an uncertainty of about 0.5 nm. The resolution is smaller than 0.1 nm. The resonance frequency of the Fabry-Perot cavity is tracked by a slave laser. Its frequency is measured against a standard laser. By using the well known relation between the resonance frequency and the displacement of the cavity mirror the frequency data can be compared with the readout of the sensor which is connected to the moving mirror. By locking the slave laser to successive resonances of the cavity the calibration range is not limited by the tuning range of the laser.

New design of micromachined capacitive force sensor

Anisotropic etching of a (110) oriented silicon wafer has been used to realize a differential capacitive force sensor. This design is based on a simple concept allowing force to be measured in the plane of the sensor, giving a new and original product in the field of small force measurements. These sensors can be adjusted to measure force in the range 0.01 N to 10 N or, in a low rigidity version, to act as a high precision displacement sensor with an expected resolution of 20 nm. These sensors are planed to be used with a commercial capacitance measurement chip (nominal capacitance: 1 pF, resolution: 1 fF).