The permanent magnetic couple is a non-contact transmission device with higher transmission efficiency than a traditional rigid transmission device. Slotting the copper conductor disc on the permanent magnetic coupler can further improve the transmission performance. This paper proposes an optimization calculation model for the slotted permanent magnetic coupler, uses ANSYS Maxwell to simulate and verifies the model to improve the transmission performance. The value of magnet pairs and the slots are 6 and 35 respectively; then we simulate output torque when the slot ratio changes from 0.5 to 0.9. The simulation results verify the accuracy of the optimization model. This paper obtains the optimization scheme of the slotted permanent magnetic coupler under different parameters. The calculation model can guide the determination of a slotted permanent magnetic coupler, which is of great significance to improve the efficiency of the transmission system.
In order to ensure the safety of construction, all kinds of construction machinery are widely applied to the construction site. Tower crane, as a material handling equipment, has the characteristics of wide operating range and large potential energy, and has become the core machinery in the construction site. The tower crane driver’s field of vision is often blocked, which seriously affects the safety of hoisting. To increase the view of tower crane drivers, most of the current monitoring systems will install a camera on the boom above the hook. But this camera can only view the situation around the hook, and it cannot be quantified. Based on this, this paper proposes a hoisting security detection technology based on deep learning. Firstly, the camera in the monitoring system is used to collect data sets. Secondly, the hook and workers are marked in the image. Then, Faster R-CNN is used to train and evaluate the data sets. The results show that the method has high recognition accuracy. However, the worker and the hook are not on a horizontal plane, so a verification test of the relationship between the height and the ratio of pixel length to true length was completed. The results show that the method can convert the ratio of the hook to the ratio of the worker, and then the real distance between the worker and the hook can be calculated.
For improving the measurement accuracy of aviation part’s profile, a high-accuracy profile measurement method based on step boundary model is proposed in this paper. Firstly, the cases of light stripe imaging in the target boundary are analysed, and the corresponding ideal boundary models are built to determine the ideal boundary locations. Then, a subpixel boundary extraction method based on feature moment is presented, which can obtain sub-pixel boundary locations on the basis of the crude boundary detection. Next, based on the reconstruction algorithms, the profile of aviation part is measured. At last, experiments using a standard part are conducted to verify the accuracy of this method and a measurement experiment is carried to verify the effectiveness of the boundary extraction. Experiment results show that the presented method can achieve the object boundary extraction in complex background interference and light environment. The extraction method can reach an accuracy of 0.056% and satisfy the requirements of field measurement.
Bolt joint, as the commonest coupling structure, is widely used in electro-mechanical system. However, it is the weakest part of the whole system. The increase of preload tension force can raise the reliability and strength of the bolt joint. Therefore, the pretension force is one of the most important factors to ensure the stability of bolt joint. According to the way of generating pretension force, the pretension force can be monitored by bolt torque, degrees and elongation. The existing bolt-loosening monitoring methods all require expensive equipment, which greatly restricts the practicality of the bolt-loosening monitoring. In this paper, a new method of bolt-loosening detection technique based on audio is proposed. The sound that bolt is hit by a hammer is recorded on the Smartphone, and the collected audio signal is classified and identified by support vector machine algorithm. First, a verification test was designed and the results show that this new method can identify the damage of bolt looseness accurately. Second, a variety of bolt-loosening was identified. The results indicate that this method has a high accuracy in multiclass classification of the bolt looseness. This bolt-loosening detection technique based on audio not only can reduce the requirements of technical and professional experience, but also make bolt-loosening monitoring simpler and easier.
KEYWORDS: Cameras, Distortion, Calibration, 3D modeling, Visual process modeling, Imaging systems, 3D image processing, 3D metrology, 3D acquisition, Cesium
The traditional vision measurement model has difficulty in guaranteeing the accuracy of measurement in the depth of field. And in this way, high-precision measurement of large components parts in three-dimensional large scale space can hardly be realized. To solve this problem, a binocular measuring method based on 3D image distortion compensation is proposed. Considering the rule of image distortion in the three-dimensional space, and combining with binocular vision measurement principle, a new binocular vision measurement model, based on 3D image distortion compensation, is established in the paper. And the model is based on the rule of image distortion in the three-dimensional space, and combined with binocular vision measurement principle. Besides, a new calibration method is proposed. This method is for the distortion parameters of the model and the intrinsic parameters of the cameras. Experimental results show that the proposed binocular vision measurement method in this paper is much more effectively than the traditional method. The results indicate that the proposed method largely improves the measurement accuracy under the condition of large depth of field. Meanwhile, this method also significantly improves the measurement accuracy in the three-dimensional space.
In order to realize the precision machining and assembly of the parts, the geometrical dimensions of the surface of the local assembly surfaces need to be strictly guaranteed. In this paper, a local high-precision three-dimensional measurement method based on line laser measuring instrument is proposed to achieve a high degree of accuracy of the three-dimensional reconstruction of the surface. Aiming at the problem of two-dimensional line laser measuring instrument which lacks one-dimensional high-precision information, a local three-dimensional profile measuring system based on an accurate single-axis controller is proposed. First of all, a three-dimensional data compensation method based on spatial multi-angle line laser measuring instrument is proposed to achieve the high-precision measurement of the default axis. Through the pretreatment of the 3D point cloud information, the measurement points can be restored accurately. Finally, the target spherical surface is needed to make local three-dimensional scanning measurements for accuracy verification. The experimental results show that this scheme can get the local three-dimensional information of the target quickly and accurately, and achieves the purpose of gaining the information and compensating the error for laser scanner information, and improves the local measurement accuracy.
An accurate measurement of large aviation part plays a key role in the assembly of aircraft. However, due to the limitation of spatial size, a calibration with large field of view and an accurate surface measurement of large part is hard to achieve. In this paper, an improved measurement method with spatial constraint calibration method and feature compression extraction method is proposed. Firstly, based on the proposed spatial constraint calibration method, the vision system is conveniently and precisely calibrated by using the designed SBA and SLT. Images of scanning laser stripes are captured by the calibrated cameras, simultaneously. Then the proposed feature compression extraction method is adopted to accurately extract centers of laser stripes. Finally, based on the binocular vision principle, the surface of part is reconstructed. The accuracy of proposed calibration method is verified in the lab. The results of the measurement of a standard part show the validity and precision of the proposed method.
In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) label-free sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/ (mg/ml) and the limit of detection was 2*10-5g/ml.
With the rapid development of high-rise buildings, the requirement of the elevator’s speed is growing higher. And the vibration amplitude of elevator will also increasing with the improvement of running speed. The vibration problems of elevator have become the important factors that affect the comfort feeling of elevator. At the same time, the strong vibration will affect the normal work of elevator, and even cause accidents. So it's necessary to study the vibration characteristics of the elevator. In recent years, smartphone has developed rapidly, with a variety of sophisticated sensors; it has the powerful data processing and transmission capacity. In this paper, the author has presented an elevator comfort monitoring method based on smartphone. This method using Monitoring App can monitor the acceleration and inclination information using MEMS sensors embedded in smartphone. Then a confirmatory test for an elevator was designed, experimental results show that elevator comfort monitoring method based on smartphone is stable and reliable.
A polymer-based multimode interference optical splitter chip has been designed and fabricated. Fiber-waveguide coupling loss as well as the structure of the multimode waveguide are optimized in the design to achieve higher performance. A simple UV-based soft nanoimprint lithography (Soft UV-NIL) technique is adopted in the fabrication. Fluorinated acrylate resins, LFR, with different refractive indices are used in this work. Both the residual layer and waveguide deformation are improved by controlling the fabrication processes. An average of 12.98 dB insertion loss is obtained from 1×4 splitters with 1.08 dB uniformity and 0.05 dB polarization-dependent loss. The validity of the polymer optical splitters fabricated through Soft UV-NIL technique is demonstrated by software simulation as well as experimental works.
In recent years, smart phone develops very fast, and it has been the most popular tool in daily life of the public. Smart phones, with powerful operating systems, data storage and processing function, varieties of high-performance sensors and easily data transmission when connected to network, are the good choice for structures status monitoring in some occasion. One kind of hoisting monitoring method was proposed in this paper based on smartphone and Monitoring App developed. Firstly, one monitoring App was designed and developed, which can monitor the acceleration and inclination information using MEMS sensors embedded in smartphone. Secondly, typical operation status model of crane hoisting was studied. Then one validation test of hoisting was designed and conducted to monitor the acceleration and inclination of different elements during the operation procedure of one crane. The test results show the feasibility of the crane hoisting safety monitoring method using smartphone.
Large-scale triangulation scanning measurement systems are widely used to measure the three-dimensional profile of large-scale components and parts. The accuracy and speed of the laser stripe center extraction are essential for guaranteeing the accuracy and efficiency of the measuring system. However, in the process of large-scale measurement, multiple factors can cause deviation of the laser stripe center, including the spatial light intensity distribution, material reflectivity characteristics, and spatial transmission characteristics. A center extraction method is proposed for improving the accuracy of the laser stripe center extraction based on image evaluation of Gaussian fitting structural similarity and analysis of the multiple source factors. First, according to the features of the gray distribution of the laser stripe, evaluation of the Gaussian fitting structural similarity is estimated to provide a threshold value for center compensation. Then using the relationships between the gray distribution of the laser stripe and the multiple source factors, a compensation method of center extraction is presented. Finally, measurement experiments for a large-scale aviation composite component are carried out. The experimental results for this specific implementation verify the feasibility of the proposed center extraction method and the improved accuracy for large-scale triangulation scanning measurements.
A simple and novel distributed tilted fiber Bragg gratings (TFBGs) based transverse load sensing system using optical
frequency domain reflectometry (OFDR) is proposed and demonstrated for the first time. The transverse load compresses
an elastomer material around the fiber and induces a broadband loss in the spectrum of the TFBG. The additional loss is
directly measured by the return loss spectrum of Fresnel reflection points introduced in the Rayleigh backscattering
trace. With the wavelength sweeping characteristic of OFDR, we realized distributed sensing by interrogating each of the
TFBGs with different wavelengths and observed a minimum crosstalk effect between sensors.
A fiber-optic sensor based on a dual polarization fiber grating laser for simultaneous measurement of temperature,
hydrostatic pressure and acoustic signal is proposed and experimentally demonstrated. The acoustic wave induces a
frequency modulation (FM) of the carrier in radio frequency (RF) range generated by the fiber laser and can be easily
extracted by using the FM demodulation technique. The temperature can be determined by the laser wavelength. The
hydrostatic pressure can be determined by monitoring the static shift of the carrier frequency and deducting the effect of
the temperature.
We experimentally demonstrate a novel fiber-optic pressure and temperature sensor using dual-FBG written in grapefruit
microstructured fiber (GMF) and standard single-mode fiber (SMF). The pressure sensitivity of FBG in GMF is much
larger than that of SMF because the large air holes in the cross section of GMF make it experience larger axial strain than
SMF in the presence of hydrostatic pressure. While the temperature responses of the two FBGs are almost the same due
to the similar material composition in the fiber cores. Hence, pressure and temperature can be simultaneously
determined.
We demonstrated a method to trim the beat frequency of dual-polarization fiber grating lasers by exposing the laser
cavity to uniform UV beam. The UV-side-illumination induces an additional birefringence of the cavity fiber and
therefore permanently changes the beat frequency of the laser. The beat frequency can be trimmed to longer or shorter
frequency range in a large frequency range. A 6-channel RF-frequency division multiplexed polarimetric fiber grating
laser sensor array was demonstrated.
In this paper we report on polarimetric distributed Bragg reflector fiber laser sensor for hydrostatic pressure. Three
different types of active fibers were used to fabricate dual-polarization distributed-Bragg-reflector fiber lasers and their
responses to hydrostatic pressure were characterized. Three fibers shown different beat frequency response to hydrostatic
pressure and a maximum pressure sensitivity of 2.28 MHz/Mpa was obtained. By detecting the double frequency signal,
the sensitivity can be further increased to 4.56 MHz/MPa. We also tested the long term stability of the sensor at 300oC.
Fiber grating laser sensors have been attracting interest because of their high signal-to-noise ratio and narrow linewidth
that permit high resolution sensing. According to the working principle, fiber grating laser sensors can be classified into
two types: wavelength encoding sensor and polarimetric heterodyning sensor. The former converts measurrand into shift
in the operation wavelength of the fiber laser, which is similar to that of fiber grating sensor. The latter converts
measurrant into change in beat frequency between the two orthogonal polarization modes from the laser. Because the
beat frequency is in radio frequency (RF) range, the polarimetric heterodyning sensor has distinctive advantages of ease
of interrogation and avoidance of expensive wavelength measurement that is required for wavelength encoding sensors.
In this paper, we report some of our recent works in fabrication of dual-polarization fiber grating lasers, development of
polarimetric heterodyning fiber grating laser sensors for measurement of acoustic wave, acceleration, lateral force,
displacement, electric current and hydrostatic pressure, and sensor multiplexing in RF domain.
We propose and demonstrate, for the first time to our knowledge, simple hydrostatic pressure sensors based on ultrashort dual-polarization distributed-Bragg-reflector fiber lasers. A bare polarimetric laser is used directly to measure the high fluid pressure up to 20 MPa. By detecting the polarization beat signal change generated from the two orthogonal polarization modes in the laser, a 0.42-MHz/Mpa pressure sensitivity and ~5-kPa resolution are achieved. For effectively enhancing the pressure sensitivity, we also exhibit a simple and accurate low-pressure sensor by designing a structure to convert the external pressure to the lateral force on the laser. This sensor shows significant and considerably high sensitivity to hydrostatic pressure of 69.2 MHz/kPa, which is almost 5 orders of magnitude higher than that of a sensor via bare lasers.
A high sensitivity displacement sensor based on a dual-polarization fiber grating laser incorporated with a cantilever
beam is demonstrated. The cantilever beam transforms the displacement into a transverse force to the fiber grating laser
which changes the fiber birefringence and therefore the polarization mode beat frequency of the laser. A sensitivity of
0.535 GHz/mm is implemented.
We present an ultra-short distributed Bragg reflector fiber laser photowritten in Er/Yb co-doped fiber. The total length of
the fiber laser is only 8.4 mm. The lasing threshold is less than 1 mW. The optical signal-to-noise ratio of the laser output
is around 70 dB. The laser emits two orthogonal polarization modes. The electrical signal-to-noise ratio of the beat signal
generated by the fiber laser is better than 70 dB.
We present a high-temperature-resistant distributed Bragg reflector fiber laser photowritten in Er/Yb codoped
phosphosilicate fiber that is capable of long-term operation at 500 °C. Highly saturated Bragg gratings are
directly inscribed into the Er/Yb fiber without hydrogen loading by using 193 nm excimer laser. After
subjected to a significant decay at elevated temperature, the stabilized gratings are strong enough for laser
oscillation. The laser operates in robust single longitude mode with output power more than 1 dBm and
signal-to-noise ratio better than 70 dB over the entire temperature range from room temperature to 500 °C.
We present a high-temperature-resistant distributed Bragg reflector fiber laser photowritten in Er/Yb codoped fiber that
is capable of long-term operating at 500°C. Highly saturated Bragg gratings are directly inscribed into the active fiber by
use of the two-photon absorption at 193 nm. After annealing at elevated temperature, the stabilized gratings are strong
enough for laser oscillation. The laser operates in robust single mode with output power more than 1 dBm and signal-tonoise
ratio better than 70 dB over the entire temperature range from room temperature to 500°C.
We report on the pressure characterization of Bragg gratings in grapefruit microstructured fibers. The air holes enhance
the pressure response. The effect of air expansion in the holes on temperature response was also investigated.
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