Angle Measurement System Research Articles

POF-IMU sensor system: A fusion between inertial measurement units and POF sensors for low-cost and highly reliable systems

Abstract This paper presents a low cost and highly reliable system for angle measurement based on a sensor fusion between inertial and fiber optic sensors. The system consists of the sensor fusion through Kalman filter of two inertial measurement units (IMUs) and an intensity variation-based polymer optical fiber (POF) curvature sensor. In addition, the IMU was applied as a reference for a compensation technique of POF curvature sensor hysteresis. The proposed system was applied on the knee angle measurement of a lower limb exoskeleton in flexion/extension cycles and in gait analysis. Results show the accuracy of the system, where the Root Mean Square Error (RMSE) between the POF-IMU sensor system and the encoder was below 4° in the worst case and about 1° in the best case. Then, the POF-IMU sensor system was evaluated as a wearable sensor for knee joint angle assessment without the exoskeleton, where its suitability for this purpose was demonstrated. The results obtained in this paper pave the way for future applications of sensor fusion between electronic and fiber optic sensors in movement analysis.

Full-circle range and microradian resolution angle measurement using the orthogonal mirror self-mixing interferometry.

The self-mixing technique based on the traditional reflecting mirror has been demonstrated with great merit for angle sensing applications. In order to solve the problems of the narrow measurement angle range and low resolution in traditional angle measurement method, we proposed an angle measurement system using orthogonal mirror self-mixing interferometry combine an orthogonal mirror with designed mechanical linkage. It overcomes the shortcomings of traditional angle measurement methods and realized the angle measurement with microradian resolution in a full-circle range of 0 rad to 2π rad. In the experiment, the measurement resolution can reach to 5.27 µrad and the absolute error can lower to ± 0.011µrad, which satisfies the requirements of most high accuracy angle measurement.

Time-resolved retardance and optic-axis angle measurement system for characterization of flexoelectro-optic liquid crystal and other birefringent devices.

A new polarimeter is presented which gives time-resolved measurements of both the optic-axis angle and the linear phase retardation for modulated birefringent optical devices. It is suitable for characterizing dynamic waveplate devices based on liquid crystal and other materials. It is fully automated and requires no angular alignment of the device under test. The system has an absolute angle error of < ± 0.3° and a retardance error of < ± 0.44°, with considerably better relative accuracy. The method has been tested with a chiral nematic liquid crystal device exhibiting flexoelectro-optic switching at 3 kHz in the uniform lying helix mode. These results represent the first time-resolved tilt-angle and phase retardation measurements for a liquid crystal device operating at fast switching frequencies.

Detection of spasticity angle of occurrence in upper limb using magnetic MoCap and construction of a severity evaluation method

Currently, in Japan, the number of patients with spasticity is increasing, along with the number of patients with injuries to the central nervous system due to an aging population. The modified Ashworth scale (MAS) is a representative method for the evaluation of spasticity in an upper limb. However, evaluation with MAS is subjective and is dependent on the experience of the attending physician. In addition, due to the low resolution of the evaluation scale used for MAS, a precise evaluation of the degree of recovery after rehabilitation for patients with spasticity and determining the effectiveness of the treatment is still a challenge. In this paper, we constructed an elbow joint angle measurement system using magnetic motion capture (MoCap) devices. We measured the flexion and extension movements of the upper limbs of patients with mild spasticity and constructed a method of detection for spasticity angle of occurrence and proposed a severity evaluation method. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Design of embedded system for optical angle measurement based on linear array CCD

Design of embedded system for optical angle measurement based on linear array CCD

基于位置敏感探测器的六自由度精密位姿测量系统

基于位置敏感探测器的六自由度精密位姿测量系统

자이로 센서를 이용한 머리의 실시간 수평 회전각 검출 시스템

본 논문에서는 자이로 센서를 이용한 머리의 실시간 수평 회전각 검출 시스템을 제안한다. 제안 방법에서는 쿼드콥터 등의 자세 제어에 이용되고 있는 저가의 자이로 센서를 이용하여 머리의 수평 회전각을 실시간으로 측정하고, C언어 기반의 오픈 소스 오디오 입출력 라이브러리인 PortAudio를 이용해 머리의 수평 회전각을 실시간으로 처리한다. 성능평가 실험 결과, 센서의 평균 갱신 시간은 검출 시간만을 고려했을 때 약 658.83μs이고, 전송 오버헤드를 포함해 약 832.77μs로 굉장히 짧게 구현되었다. 또한, 측정된 드리프트 오차의 기울기는 직선에 매우 가까웠고, 평균 기울기는 -0.1406deg/s였다. 실제 사용자의 머리 움직임을 측정한 결과, 제안 시스템을 이용하면 사용자 머리의 수평 회전각을 실시간으로 측정할 수 있음을 증명하였다.

Low-Cost Contact Angle Measurement System for QCM Sensor

Hydrophobicity is one of the importance factors in the surface properties of materials. This work presents the development of a low-cost contact angle measurement system based on goniometric measurement using a low-cost digital camera, tilt control system for surface alignment and curvature approximation algorithm to determine the contact angle between the solid and spherical cap of a water droplet. The design is specifically targeted for measuring the contact angle of a Quartz Crystal Microbalance sensor in the form of HC-49/U with a disc diameter of 8.7mm.The contact angle measurement using goniometric measurement depends on the quality of captured image and calculation method for the angle determination. Proper alignment of the sample surface is required to minimize the discrepancy of the angle measurement of water drop surface profile caused by gravity. A PIC18F4550 microcontroller is used to control the motorized tilt platform to reduce the discrepancy between left and right contact angle value. Circle fit algorithm to determine the contact angle value from the captured image is used. Using the motorized tilt control system and circle fit algorithm, the developed contact angle measurement system able to measure the contact angle with discrepancy less than 1 O .

Method to measure the position offset of multiple light spots in a distributed aperture laser angle measurement system.

In this paper, an accurate measurement method of multiple spots' position offsets on a four-quadrant detector is proposed for a distributed aperture laser angle measurement system (DALAMS). The theoretical model is put forward, as well as the corresponding calculation method. This method includes two steps. First, as the initial estimation, integral approximation is applied to fit the distributed spots' offset function; second, the Boltzmann function is employed to compensate for the estimation error to improve detection accuracy. The simulation results attest to the correctness and effectiveness of the proposed method, and tolerance synthesis analysis of DALAMS is conducted to determine the maximum uncertainties of manufacturing and installation. The maximum angle error is less than 0.08° in the prototype distributed measurement system, which shows the stability and robustness for prospective applications.

High resolution and stability roll angle measurement method for precision linear displacement stages.

A method for high resolution roll angle measurement of linear displacement stages is developed theoretically and tested experimentally. The new optical configuration is based on a special differential plane mirror interferometer, a wedge prism assembly, and a wedge mirror assembly. The wedge prisms assembly is used as a roll angle sensor, which converts roll angle to the changes of optical path. The special interferometer, composed a polarization splitter plane, a half wave plate, a beam splitter, a retro-reflector and a quarter wave plate, is designed for high resolution measurement of the changes of the optical path. The interferometric beams are a completely common path for the adoption of the centrosymmetrical measurement structure, and the cross talk of the straightness, yaw, and pitch errors is avoided. The angle measurement resolution of the proposed method is 3.5 μrad in theoretical with a phase meter which has a resolution of 2π/512. The experimental result also shows the great stability and accuracy of the present roll angle measurement system.

Measurement of finger joint angle using a flexible polymer sensor

This paper aims to develop a measurement system for the finger joint angle by using a flexible polymer sensor. In rehabilitation, it is important to evaluate human motions quantitatively for effective treatment. In this study, we focus on hand's grasping motion, which is important motion for eating and drinking. About the flexible polymer sensor, in the previous studies, it has been elucidated that the outputs from the flexible polymer sensor are proportional to the average curvature of measuring surface. Therefore, using the sensor, finger bending motion can be measured by attaching the sensor on finger surface. Firstly, the relationship between the average curvature of finger surface and finger joint angle is theoretically investigated. Then, in order to obtain the relationship between sensor outputs and finger joint angles, sensor outputs and finger joint angles during grasping acrylic cylinders are measured. From the results, it was found that the developed system is useful to measure the finger joint angles.

A ultra-small-angle self-mixing sensor system with high detection resolution and wide measurement range

The self-mixing technique based on the traditional reflecting mirror has been demonstrated with great merit for angle sensing applications. Here we demonstrate a modified self-reflection-mixing angle measurement system by combine a right-angle prism to self-mixing angle measurement. In our system, the wavelength is crucial to the angle measurement resolution. For a microchip solid-state laser, the measurement resolution can reach 0.49mrad, while the resolution for the He-Ne laser is 0.53mrad. In addition, the ranges in the system with the microchip solid-state laser and He-Ne laser are up to 22mrad and 24.9mrad respectively. This modified angle measurement system effectively combines the advantage of self-mixing measurement system with a compact structure, providing interesting features such as of high requisition of resolution and precision.

Enhanced photocatalytic activity of micro/nano textured TiO2 surfaces prepared by sandblasting/acid-etching/anodizing process

In this study, micro-textured titanium surfaces were created by sandblasting and acid-etching methods. Nanostructured titanium dioxide (TiO2) films were synthesized on the micro-textured titanium surfaces by anodizing method. Subsequently, anodized (A), acid-etched/anodized (EA), sandblasted/anodized (SA) and sandblasted/acid-etched/anodized (SEA) samples were fabricated. Structural and morphological properties of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, surface roughness and wettability of the samples were evaluated by means of profilometry and contact angle measurement systems, respectively. Finally, the photocatalytic activities of the samples were determined by using aqueous methylene blue (MB) solutions under a specific UV light illumination for different periods of time. The obtained results pointed out that sandblasting and acid-etching treatment improved the surface roughness of the samples significantly. The photocatalytic experimental results showed that micro-textured surface accelerated the degradation of MB, if compared to samples which are anodized without any of the regarding surface treatments. To sum up, sandblasted/acid-etched/anodized titanium surfaces exhibited the highest wettability, surface roughness and photocatalytic activity among the samples. The present study may shed new light on the modification of titanium surfaces.

Effects of black silicon surface structures on wetting behaviors, single water droplet icing and frosting under natural convection conditions

Abstract In this research, the effects of black silicon and two-stage black silicon surface structures on the characteristics of wetting, icing process of a single water droplet, and frost accumulation under natural convection conditions were investigated. Black silicon and two-stage black silicon surfaces were first designed and fabricated, and then examined by means of scanning electron microscopy (SEM). Wetting behavior was measured by contact angle measurement system. The icing and frosting processes were acquired through high-speed photography. The test surfaces were cooled down from room temperature to well below 0 °C by circulating ethyl alcohol via a constant temperature system. The results show that compared with uncoated silicon, black silicon and two-stage black silicon surfaces can largely increase the surface hydrophobicity, reduce the freezing thickness deformation and show anti-frosting performance. This study provides a new type of hydrophobic surface structure and plays an important role in designing anti-icing/anti-frosting surfaces for practical applications.

Large field distributed aperture laser semiactive angle measurement system design with imaging fiber bundles.

A type of laser semiactive angle measurement system is designed for target detecting and tracking. Only one detector is used to detect target location from four distributed aperture optical systems through a 4×1 imaging fiber bundle. A telecentric optical system in image space is designed to increase the efficiency of imaging fiber bundles. According to the working principle of a four-quadrant (4Q) detector, fiber diamond alignment is adopted between an optical system and a 4Q detector. The structure of the laser semiactive angle measurement system is, we believe, novel. Tolerance analysis is carried out to determine tolerance limits of manufacture and installation errors of the optical system. The performance of the proposed method is identified by computer simulations and experiments. It is demonstrated that the linear region of the system is ±12°, with measurement error of better than 0.2°. In general, this new system can be used with large field of view and high accuracy, providing an efficient, stable, and fast method for angle measurement in practical situations.

Design and implementation of a high-resolution angle measurement system for the upper limbs using a low-cost servomotor

The study of biomechanics of the human body is of great importance in many areas such as rehabilitation, sports, military industry, in the design and manufacture of prosthetics and orthotics, in creating man-machine interfaces, etc. Therefore, we present the technology and the design of a portable angular measurement device with high resolution and low costs, for position, velocity, acceleration, repetitions per time unit, delay and amplitude of the movement for the arm and the forearm. This device is based on an embedded servo motor with an encoder with a resolution of 0.088 degrees, making it much more accurate than similar devices created for this type of research. The physical dimensions of the device and its low weight make it a useful tool. Among the design parameters the low cost and ease in construction was considered in a way that the device is easy to replicate. Information obtained by this device allows analyzing the movement of the arm and the forearm, and with this detecting or diagnosing symptoms of health problems, progress in fitness and the creation of man-machine interfaces for interaction with virtual environments.

Simple and Green Fabrication of a Superhydrophobic Surface by One-Step Immersion for Continuous Oil/Water Separation.

In this paper, stainless steel meshes with superhydrophobic and superoleophilic surfaces were fabricated by rapid and simple one-step immersion in a solution containing hydrochloric acid and stearic acid. The apparent contact angles were tested by a video contact angle measurement system (CA). Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the surface topographies and chemical compositions. The SEM results showed that mesh surfaces were covered by ferric stearate (Fe[CH3(CH2)16COO]2) with low surface energy. The CA test results showed that the mesh had a maximum apparent contact angle of 160 ± 1.0° and a sliding angle of less than 5.0° for the water droplet, whereas the apparent contact angle for the oil droplet was zero. Ultrasound oscillation and exposure tests at atmospheric conditions and immersion tests in 3.5 wt % NaCl aqueous solution were conducted to confirm the mesh with excellent superhydrophobic and superoleophilic properties. On the basis of the superhydrophobic mesh, a miniature separation device pump was designed to collect pure oil from the oil/water mixture. It showed that the device was easier and convenient. The techniques and materials presented in this work are promising for application to wastewater and oil spill treatment.

An angle measurement system of high resolution for the upper limbs using a low-cost servomotor

In the here presented study, the biomechanical design and coupling of a servomotor as measuring element for determining the angle of elbow flexion in humans is presented. This task requires a digital servomotor with a 12-bit low charge encoder type ’’contactless absolute”, which makes the holding torque negligible. Because the servomotor is used as a sensor and not as an actuator, and is expected to produce the least possible resistance to the movement of the elbow, this is a crucial point. Additionally, the biomechanical design of the structure for coupling the servomotor was carried out considering the different movements of the arm and forearm, and the necessity to not interfere with the natural movement of the arm. The measurement resolution allows obtaining the flexion angle to an accuracy of 0.088; and integrated into the embedded system used to communicate with the servomotor, that allows obtaining and analyzing data and temporarily integrating information for counting repeats or measuring the speed of movements, among others. This system will also be useful to calibrate and compare other compatible biomechanical analysis models, where the same movement is analyzed.

Kinematic and dynamic errors during the measurement of linear displacements using the angle transducers

Dependence of linear displacement error, while measuring with angle transducers, on angle measurement system errors, kinematic and geometric errors of mechanism of linear motion transformation to rotation is shown. Dynamic processes, acting in an elastic element, connecting a movable compound, which linear displacement is measured, with the shaft of the angle measurement transducer, are modeled. Vibration modes, influencing the uncertainty of linear displacement measurement by an angle transducer, are defined. Results of numerical study by using FEM are verified and complemented by experimental research. Research stands and equipment are described.DOI: http://dx.doi.org/10.5755/j01.mech.22.3.14180

Facile fabrication of superhydrophobic silica coatings with excellent corrosion resistance and liquid marbles

Self-cleaning superhydrophobic coatings with water contact angle as high as 156° and sliding angle as low as 3° were prepared through a facile one-step spray coating process by spraying the hydrophobic silica nanoparticles onto Al substrate. In addition, the superhydrophobic coatings maintained excellent electrochemical corrosion resistance in a 3.5 wt% NaCl aqueous solution. The corrosion behavior of the superhydrophobic coatings on the Al substrate was characterized by the polarization curve and electrochemical impedance spectroscopy. The results indicated that the superhydrophobic coatings possessed excellent corrosion resistance. In addition, liquid marbles coated with hydrophobic silica nanoparticles were prepared by gentle rolling of liquid on powder beds of hydrophobic silica nanoparticles. Furthermore, water evaporation from the silica shell with time evolution was investigated using a contact angle measurement system video camera. Superhydrophobic silica surface with excellent corrosion resistance and liquid marbles coated with hydrophobic silica were fabricated by a facile process.