Two-axis Tilt Research Articles

경제적인 on/off 밸브와 2축 각도센서를 이용한 유압구동 Platform 수평제어 장치 개발

In transportatinon using heavy ships or airplanes, the most important criterion is maintaining the horizontal state. Previously, most studies used expensive servo valves to solve this control problem. However, herein, a square platform is controlled economically using on/off valves and a two-axis tilt sensor. When the angle values detected by the tilt sensor are transmitted to the PLC, four hydraulic cylinders connected to the on/off valves can control the horizontal state of the platform using the proposed algorithms. This study confirms that stable balancing can be maintained by testing at various loads. Further, various target angles are tested to confirm the proposed horizontal control scheme. Therefore, an efficient horizontal control system can be established and is expected to be of help to various applications.

Study on Design Optimization of a Symmetry Two-Axis Tilt Angle Capacitive Sensor

This paper presents the design, optimization, fabrication and characterization of a symmetrical two-axis tilt angle sensor. The sensor consists of a globe-calotte-shaped excitation electrode and two pairs of sensing electrodes of the same dimensions, positioned symmetrically on a 3D printed hollow sphere. The sphere is filled with oil and air, and then mounted on the surface of a printed circuit board (PCB) for mechanical packaging and measurement. Experimental results show that the sensor can measure the tilt angle in both the x- and y-axes with sensitivity of 124 mV/° and resolution of ±0.15° in the range from −35° to 35°. The characteristics of the sensor on the x- and y-axes are similar. The proposed sensor can be used in several applications.

Study on Design Optimization of a Capacitive Tilt Angle Sensor

This paper presents a design optimization and validation of a two-axis cylindrical capacitive tilt angle sensor. The proposed sensor includes of five electrodes symmetrically arranged surrounding an air–liquid two phases cylindrical tube, forming two pairs of electrodes for roll and pith angle measurement. Cylindrical plastic tube filled partly with dielectric fluid with dielectric constant of 2. The proposed sensor can detect tilt angles in x-axis and y-axis, i.e. roll and pith angles. When the cylindrical plastic tube is rotated, the dielectric fluid covers a portion of the induction electrodes, thereby changing the differential capacitance value of the capacitor corresponding to the tilt angle. By measuring the capacitance change, the tilt angle can be estimated. Performance of the sensor was investigated by Finite element method using Comsol Multiphysics simulation software. Simulation results show the variation in capacitance with respect to the variation of tilt angle. Based on this simulation model, the structure of the electrodes was manipulated for maximizing the sensitivity for roll and pith sensing in an appropriate working range. Experiments were also conducted for validation. The experiment results are well matched with simulated results. The optimized sensor has working range from −70° to +70° with sensitivity of 3 mV/° in the roll angle and from −30° to +30° with sensitivity of 17 mV/° in the pitch angle.

Symmetry Two-axis Tilt Angle Capacitive Sensor System

Abstract: This paper presents the design, fabrication and operation of a highly symmetrical two-axis capacitive sensor. The proposed sensor consists of five electrodes, including of an excitation electrode and two pairs of sensing electrodes with exactly the same dimensions, arranged at identified symmetrically locations on a 3D printed hollow sphere, which containing dielectric medium formed by the partly filled oil and the remaining air. The proposed sensor can measure the tilt angle about the x-axis and y-axis with symmetrical outputs. The proposed sensor is fabricated using a rapid prototyping technology and mounted on the surface of a printed circuit board (PCB) for mechanical packaging and signal processing. Experimental measurement results show that the sensor system can measure the tilt angle in both the x- and y-axis with sensitivity of 103 mV/degree and resolution of ±1 degree in the range of -30 degree to +30 degree. This sensor system can be used in many military and consumer applications.
 Keywords: Capacitive sensor, Fluidic sensor, Two-axis tilt angle sensor.

A two-axis tilt control system on a turntable for rotating-optical-cavity experiments.

Many precision measurements using rotating optical cavities have tight requirement on the level of a rotating platform on which the cavities are installed. We develop a single-stage tilt control system as one part of the experimental setup for testing Lorentz invariance using two optical cavities that are perpendicular to each other. Home built voice-coil actuators, together with a tilt sensor and control electronics, are adopted to simultaneously suppress the tilt of the rotating platform in two orthogonal directions. The large cross coupling between two orthogonal axes is observed, and its mechanism is examined. By adding a compensating weight, the loop instability resulting from the cross coupling is effectively removed. With the active control, the variation of the tilt around each of the two axes is reduced from the free-running value of ±30 µrad to within ±0.2 µrad, independently measured by using a second tilt sensor. This residual tilt has a component at the rotational frequency with an amplitude of 0.1 µrad, which contributes a systematical offset of 1.8 × 10-17 to the Lorentz violating parameter κ e- ZZ, estimated by assuming that the tilt sensitivity of the optical cavity is 1 × 10-16/μrad. Further improvement is still possible by using piezo-electric actuators that exhibit higher resonant frequencies, a different approach that will suppress the residual variation of the tilt to within ±0.01 µrad and allow a reduced systematical offset of 1.8 × 10-18 for κ e- ZZ.

A Robust Two-axis Tilt Angle Sensor Based on Air/Liquid Two-phase Dielectric Capacitive Sensing Structure

ABSTRACT This paper presents the design, fabrication, and characterization of a two-axis tilt angle sensor based on the air/liquid two-phase dielectric capacitive sensing structure. The sensor consists of five electrodes, one serves as the exciting electrode and two pairs of electrodes as sensing ones, which are arranged at identical positions surrounding a glass cylinder tube. The glass cylinder tube is partly filled with dielectric liquid to form the air/liquid two-phase dielectric medium. Based on this arrangement, the proposed sensor can detect roll and pitch angles, simultaneously. A computational simulation and experimental measurements are performed to study the performance of the sensor. The numerical simulation is carried out with a finite element analysis using COMSOL. A prototype of the sensor was fabricated, and its performance was evaluated. The tilt angle sensor was employed on a printed circuit board with a conditioning circuit, consisting of a sine wave generator, pre-amplifiers, rectifiers, and low pass filters. The experiment results confirmed that the roll angle detection has a linear range in the range of −60° to +60° with non-linearity error of 6.6%. The sensitivity and resolution in this range are 18.2 mV/° and 0.55°, respectively. For pitch angle detection, the linear range is −16° to +16° with non-linearity of 10%, and sensitivity and resolution of 58.2 mV/° and 0.17°, respectively.

Demonstration for a two-axis interferometric tilt sensor in KAGRA

Recently, a folded Mach–Zehnder interferometer with homodyne in- and quadrature-phase detection was proposed as a high-precision, wide-dynamic range tilt sensor. By way of a practical application and to validate actual performance, two-axis tilt sensors were developed and installed for one mirror of the input mode cleaner cavity in KAGRA, the large-scale cryogenic gravitational-wave telescope in Kamioka, Gifu, Japan. Building on previous work, we have demonstrated that the two-axis tilt sensor has properly sensed the tilt angle changes of the mirror motion with high precision and without calibration. Compared with our initial angular sensor, an optical lever, which is calibrated by using the interferometer tilt sensor, we found that both sensors showed actual tilt motions of the mirror at low frequencies, and the two-axis interferometer sensor has a better sensitivity at higher frequencies.

Design and Testing of a Flexible Inclinometer Probe for Model Tests of Landslide Deep Displacement Measurement.

The physical model test of landslides is important for studying landslide structural damage, and parameter measurement is key in this process. To meet the measurement requirements for deep displacement in landslide physical models, an automatic flexible inclinometer probe with good coupling and large deformation capacity was designed. The flexible inclinometer probe consists of several gravity acceleration sensing units that are protected and positioned by silicon encapsulation, all the units are connected to a 485-comunication bus. By sensing the two-axis tilt angle, the direction and magnitude of the displacement for a measurement unit can be calculated, then the overall displacement is accumulated according to all units, integrated from bottom to top in turn. In the conversion from angle to displacement, two spline interpolation methods are introduced to correct and resample the data; one is to interpolate the displacement after conversion, and the other is to interpolate the angle before conversion; compared with the result read from checkered paper, the latter is proved to have a better effect, with an additional condition that the displacement curve move up half the length of the unit. The flexible inclinometer is verified with respect to its principle and arrangement by a laboratory physical model test, and the test results are highly consistent with the actual deformation of the landslide model.

Design and Testing of a 2D Optical Fiber Sensor for Building Tilt Monitoring Based on Fiber Bragg Gratings

In this paper, a new type of optical fiber tilt sensor based on fiber Bragg grating (FBG) is presented for 2D dual-axis tilt angle sensing. The tilt sensor is composed of two cylindrical floats suspended in water, connected with FBG. When the external environment causes the tilting of the sensor, the surface of the liquid within the container will form a new balanced liquid surface plane due to the gravity and change the height of the liquid at different locations in the container. So the buoyancy force of the cylindrical floats of the sensor will vary with the depth of liquid, thus the changed FBG strain will cause the FBG reflection central wavelength shift. According to the measured central wavelength shift by the optical spectral analyzer (OSA), we can obtain the two-axis tilt angle of the sensor. The proposed sensor can detect a tilt angle range of −5 degrees to +5 degrees and achieve a sensitivity of 0.1° with optical spectrum analyzer resolution of 0.01 nm. Due to its good sensing linearity, the proposed sensor can be applied in building tilt measurement.

Robust optic alignment in a tilt-free implementation of the Rowland circle spectrometer

High-resolution x-ray emission spectroscopy (XES) has recently been demonstrated in the laboratory setting, achieving nearly synchrotron-level count rates despite the use of only conventional x-ray tube sources. This development holds high potential for expanding the reach of x-ray spectroscopies beyond the specialist community of synchrotron users, but comes with its own unique technical challenges for instrument performance and also, just as importantly, for ease of use by non-experts in x-ray science. Here, we address spectrometer design and operations in the context of the imperfect parallelness between the desired crystal plane and the wafer surface in spherically bent crystal analyser (SBCAs), an effect usually called “wafer miscut”. This introduces an ambiguous re-focusing error that typically requires a motorized two-axis tilt stage for fine alignment of the SBCA optic onto the ideal Rowland circle configuration. We instead demonstrate an asymmetric Rowland geometry that eliminates all need for motorized fine-tilt adjustment. We find rapid, extremely reproducible re-insertion of any aligned SBCA, i.e., without the need for any subsequent reoptimization. These improvements strongly benefit the ease of use of laboratory based spectrometers, taking them an important step closer to the level of turnkey operations needed for wide adoption outside of the existing specialist community.

基于数字天顶仪的双轴倾角仪研究

基于数字天顶仪的双轴倾角仪研究

MEMS Gyro Aided Calibration of Electronic Compass

In this paper, an MEMS gyro aided on line calibration algorithm for electronic compass is presented. This electronic compass module consists of a three-axis AMR sensor, a two-axis MEMS tilt sensor and a one-axis MEMS gyro. The automatic calibration method requires to rotate the electronic compass two full 360-degree revolution. In this rotation procedure, magnetic field data, attitude data and angular rate data are recorded. Based on recorded magnetic field data and attitude data, raw heading data is calculated. This raw heading data is verified by angular rate output of MEMS gyro. Results of experiment show that the accuracy of calibrated compass is better than 0.5 deg and MEMS gyro aided on line calibration algorithm is effective for electronic compass.

An interferometric calibration system for various linear artefacts using active compensation of angular motion errors

A calibration system for linear-dimension artefacts was developed, which employed a multi-axis laser interferometer for direct metrological traceability and active compensation of angular motion errors. It can calibrate various end and line standards by changing probes (contact and optical probe). We designed the system as a moving probe type with a cantilever structure to reduce overall size and increase efficiency in calibration. A stage part including a two-axis tilt stage provides precise linear motion of a probing part over the range of 2000 mm with nanometric resolution. The three-axis interferometer measuring linear and rotational motions of the stage enables us to obtain probing position and compensate angular motion errors precisely. It was also arranged to minimize the Abbe offset, and so the Abbe error can be reduced remarkably combining the active compensation of angular motion errors. The overall system was installed in a temperature-controlled chamber to decrease thermal variation during measurements. The measurement uncertainty of the calibration system was analysed by considering the performance of the main components. We measured several long gauge blocks and a precision line scale, and compared the measured values with the reference ones and also checked their stabilities. Their deviations were less than 100 nm and existed within the expanded measurement uncertainty (k = 2).

Programmable imaging with two-axis micromirrors

We demonstrate a means of creating a digital image by using a two-axis tilt micromirror to scan a scene. For each different orientation we extract a single gray scale value from the mirror and combine them to form a single composite image. This allows one to choose the distribution of the samples, and so in principle a variable resolution image could be created. We demonstrate this ability to control resolution and projection by constructing a voltage table that compensates for the nonlinear response of the mirrors to the applied voltage.

Analysis of a combined tip-tilt and deformable mirror

A deformable mirror mounted on a two-axis tilt platform can provide wavefront compensation at a single location in an adaptive optics system, resulting in a significant reduction in the number of optical components in the system and in a simplification of the alignment. However, the moment of inertia of a deformable mirror is significantly different from that of the monolithic mirror commonly mounted on a tilt platform. We report on what are to our knowledge the first experimental results of mounting a microelectromechanical deformable mirror onto a fast steering platform and the first observation that at low operating frequencies high-order deformation of the deformable mirror membrane was not recorded.

A two-axis tilt sensor based on optics

A two-axis tilt sensor, consisting of two lenses and a CMOS image sensor, based on refractive law, is described here. This two-lens optical system, which has a bowl-shaped lens, is designed in such a way that one can find the tilt information for the total system. Indeed, the relationship between the tilt angle and the position of the light spot on the sensor is easy to observe directly. The reading tilt angle can be estimated with a resolution of better than 4.2 arcsec. This tilt sensor would be suitable for laboratory, civil engineering and industrial applications.

Radial and Tangential-Tilt Servo Using Four-Axis Actuator

A two-axis tilt servo using a four-axis object-lens actuator was developed. The four-axis actuator can tilt the object lens in the radial and tangential directions, and can move it to allow axial tracking or radial tracking. The tilt servo was applied on an optical disc system for next-generation digital versatile discs using a blue-violet laser, and the effect of disc-tilt compensation was determined experimentally. These experiments show that the tilt servo with the four-axis object lens actuator reduces tilt by 0.1 deg in the cases of a disc tangential tilt to 0.43 deg and a disc radial tilt to 0.47 deg.

A Three-Dimensional Micro-Electro-Mechanical System (MEMS) Optical Switch Module Using Low-Cost Highly Accurate Polymer Components

This paper describes a large-scale, compact three-dimensional (3D) micro-electro-mechanical system (MEMS) optical switch using two-axis tilt mirror arrays and free-space optics. This switch structure provides a practical solution for constructing a large-scale switching fabric due to its high density and low cost features. The MEMS mirrors are made of single-crystal silicon with integrated gimbal structures and are tilted two dimensionally by electrostatic force. In the mirrors, the driving electrode has a three-dimensional terrace structure and they effectively reduce the control voltage compared with conventional MEMS mirrors. The free-space optics consists of low-cost high-precision polymer components and is passively assembled in a series of simple steps. A prototype module with 100-channel optical fiber input/output has an overall hardware volume of approximately 170 cc (80×60×35 mm), and this exhibited a low coupling loss of 4.0 dB and a switching time of 3 msec.

A self-aligned vertical comb-drive actuator on an SOI wafer for a 2D scanning micromirror

A self-aligned vertical comb-drive actuator for a two-axis tilt scanning micromirror is presented. Self-alignment between moving and fixed fingers is essential in order to avoid lateral instability leading to an in-plane rotational pull-in during an actuation. Multilayered masking films have been utilized to fabricate the self-aligned comb fingers. To generate high electrostatic torque, high-aspect ratio comb-drive actuators with 40 µm thick fingers have been realized on a silicon-on-insulator (SOI) wafer utilizing deep reactive ion etching (DRIE) technology. A delay-mask process (DMP) was employed in an etching step of a silicon device layer to assist etching of a buried oxide (BOX) layer at the bottom of narrow (5 µm) and deep (40 µm) silicon trenches. The DC mechanical scan angles of the actuators employed in the two-axis tilt, gimbal-configured micromirror were measured as ±2.1° at 48 V around an inner axis and ±1.8° at 44 V around an outer axis, respectively. The fabricated micromirror with a mirror area of 1 mm × 1 mm has mechanical resonant frequencies of 1.2 kHz around the inner axis (a mirror only) and 0.9 kHz around the outer axis (a frame and the mirror), respectively.

Three-dimensional distributions of elements in biological samples by energy-filtered electron tomography

By combining electron tomography with energy-filtered electron microscopy, we have shown the feasibility of determining the three-dimensional distributions of phosphorus in biological specimens. Thin sections of the nematode, Caenorhabditis elegans were prepared by high-pressure freezing, freeze-substitution and plastic embedding. Images were recorded at energy losses above and below the phosphorus L 2,3 edge using a post-column imaging filter operating at a beam energy of 120 keV. The unstained specimens exhibited minimal contrast in bright-field images. After it was determined that the specimen was sufficiently thin to allow two-window ratio imaging of phosphorus, pairs of pre-edge and post-edge images were acquired in series over a tilt range of ±55° at 5° increments for two orthogonal tilt axes. The projected phosphorus distributions were aligned using the pre-edge images that contained inelastic contrast from colloidal gold particles deposited on the specimen surface. A reconstruction and surface rendering of the phosphorus distribution clearly revealed features 15–20 nm in diameter, which were identified as ribosomes distributed along the stacked membranes of endoplasmic reticulum and in the cytoplasm. The sensitivity of the technique was estimated at <35 phosphorus atoms per voxel based on the known total ribosomal phosphorus content of approximately 7000 atoms. Although a high electron dose of approximately 10 7 e/nm 2 was required to record two-axis tilt series, specimens were sufficiently stable to allow image alignment and tomographic reconstruction.