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In this investigation, a linear encoder system based on the ultrasonic transducer has been proposed. Ultrasonic transducers are usually designed for distance measurements, such as the time of flight method and sonar system. These applications are defined as discrete-length measurement technologies. The purpose of this study is to develop a continuous displacement measurement system using ultrasonic transducers.

A modified signal processing based on heterodyne signaling is implemented in this system. In the proposed signal processing, there is an automatic gain control module, a phase-shifting module, a phase detection module, an interpolation module and especially a frequency multiplication module, which can enhance the resolution and reduce the interpolation error simultaneously.

The proposed system can generate the encoding signals and is compatible with most motion control systems. For the experimental result, the maximum measurement error and standard deviation are about −0.027 and 0.048 mm, respectively. It shows that the proposed encoder system has the potential for displacement measurement tasks.

This study reveals an ultrasonic linear encoder that is capable of generating an incremental encoding signal, accompanied by a corresponding signal processing methodology. In contrast to the conventional heterodyne signal processing approach, the proposed multiplication method effectively reduces the interpolation error that arises because of multiple reflections.

The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal lubrication state. The oil film thickness is a crucial parameter reflecting the lubrication status of bearings, directly influencing the operational state of bearing transmission systems. However, it is challenging to accurately measure the oil film thickness under traditional disassembly conditions due to factors such as bearing structure and working conditions. Therefore, there is an urgent need for a nondestructive testing method to measure the oil film thickness and its status.

This paper introduces methods for optically, electrically and acoustically measuring the oil film thickness and status of bearings. It discusses the adaptability and measurement accuracy of different bearing oil film measurement methods and the impact of varying measurement conditions on accuracy. In addition, it compares the application scenarios of other techniques and the influence of the environment on detection results.

Ultrasonic measurement stands out due to its widespread adaptability, making it suitable for oil film thickness detection in various states and monitoring continuous changes in oil film thickness. Different methods can be selected depending on the measurement environment to compensate for measurement accuracy and enhance detection effectiveness.

This paper reviews the basic principles and latest applications of optical, electrical and acoustic measurement of oil film thickness and status. It analyzes applicable measurement methods for oil film under different conditions. It discusses the future trends of detection methods, providing possible solutions for bearing oil film thickness detection in complex engineering environments.

Seam pucker is one of the most important aspects of garment quality in the sewing process. Recently, automatic sewing systems have been developed and seam pucker or other defects would have to be automatically inspected in these systems. Two systems of automatic, contactless measurement of seam pucker have been developed. One of the measurement systems, with which surface shape of seam pucker was measured, is based on laser technology. Intensity of reflected ultrasonic wave is measured using another measurement system. The laser measurement system has been applied to moderate or severe seam pucker and the ultrasonic wave system has been applied to the accurate evaluation of very small seam pucker. The result of the evaluation by machine has to match the result of subjective evaluation by humans. To verify this, samples of seam pucker were evaluated using five judges. With the measurement data of surface shape of these samples, the power spectra of the wave form of seam pucker are calculated. Analyses and correlates the relationship between objective measurement and subjective evaluation by discriminant analysis, with the result of subjective evaluation and the power spectra of the samples. Having obtained these relationships, the degree of seam pucker can be measured objectively by both systems.

This article aims to propose a new measurement method for ultrasonic power based on self-reciprocity theorem which turns the estimation of ultrasonic power to the measurement of first echo current and open-circuit voltage of the driving source.

The formula for ultrasonic power is derived which has corrected the position of pressure reflection coefficient on the interface of water and steel. The diffraction correction for focusing transducers is evaluated using numerical computation of the Rayleigh integral. One way to estimate the reflection coefficient of focusing beams on heterogeneous interface is also depicted.

Comparison experiment with radiation force balance method demonstrates that ultrasonic power measurement using self-reciprocity is sound in theory and feasible in practice.

It has a better capability of anti-environmental interference and, thus, can be extended to low-level and high-frequency power measurements.

The purpose of this study is to develop an electromagnetic loading method for online measurement of the acoustoelastic coefficients and bus bar plane stress.

A method based on the combination of electromagnetic loading and the acoustoelastic effect is proposed to realize online measurement of acoustoelastic coefficients and plane stress. Electromagnetic loading is performed on the bus bar specimen, and the acoustoelastic coefficients and the bus bar plane stress are obtained by the ultrasonic method. An electromagnetic loading experimental platform is designed to provide electromagnetic force to the metal plate, including an electromagnetic loading module, an ultrasonic testing module and a stress simulation module.

The feasibility of the proposed electromagnetic loading method is proved by verification experiments. The acoustoelastic coefficients and plane stress measured using the electromagnetic loading method are more accurate than those measured using the traditional method.

The proposed electromagnetic loading method provides a new study perspective and enables more accurate measurement of the acoustoelastic coefficients and plane stress. The study provides an important basis for evaluating the operation status of electrical equipment.

In the context of fixed-wing aircraft wing assembly, there is a need for a rapid and precise measurement technique to determine the center distance between two double-hole components. This paper aims to propose an optical-based spatial point distance measurement technique using the spatial triangulation method. The purpose of this paper is to design a specialized measurement system, specifically a spherically mounted retroreflector nest (SMR nest), equipped with two laser displacement sensors and a rotary encoder as the core to achieve accurate distance measurements between the double holes.

To develop an efficient and accurate measurement system, the paper uses a combination of laser displacement sensors and a rotary encoder within the SMR nest. The system is designed, implemented and tested to meet the requirements of precise distance measurement. Software and hardware components have been developed and integrated for validation.

The optical-based distance measurement system achieves high precision at 0.04 mm and repeatability at 0.02 mm within a range of 412.084 mm to 1,590.591 mm. These results validate its suitability for efficient assembly processes, eliminating repetitive errors in aircraft wing assembly.

This paper proposes an optical-based spatial point distance measurement technique, as well as a unique design of a SMR nest and the introduction of two novel calibration techniques, all of which are validated by the developed software and hardware platform.

Accurately, positioning is a fundamental requirement for vision measurement systems. The calculation of the harvesting width can not only help farmers adjust the direction of the intelligent harvesting robot in time but also provide data support for future unmanned vehicles.

To make the length of each pixel equal, the image is restored to the aerial view in the world coordinate system. To solve the problem of too much calculation caused by too many particles, a certain number of particles are scattered near the crop boundary and the distribution regularities of particles’ weight are analyzed. Based on the analysis, a novel boundary positioning method is presented. In the meantime, to improve the robustness of the algorithm, the back-projection algorithm is also used for boundary positioning.

Experiments demonstrate that the proposed method could well meet the precision and real-time requirements with the measurement error within 55 mm.

In visual target tracking, using particle filtering, a rectangular is used to track the target and cannot obtain the boundary information. This paper studied the distribution of the particle set near the crop boundary and proposed an improved particle filtering algorithm. In the algorithm, a small amount of particles is used to determine the crop boundary and accurate positioning of the crop boundary is realized.

The reduced ability of eyes to see clearly even with the use of glasses is known as the state of visual impairment. Among the many challenges faced, outdoor travel is one of them requiring to travel through surfaces, which has potholes and bumps.

The depth of the pothole and height of the bump is also conveyed to the user through different vibration pattern of various intensity. With available electronic travel aids, the visually impaired persons are still more inclined to rely on their white cane than carrying additional equipment for obstacle avoidance. In the system, all the components can be attached to the white cane, requiring no additional device to carry.

Upon experimentation with different obstacle types, the system obtained a 24.88% higher score in comparison to normal walking cane. A comparison with the state of the art available systems is also provided.

Moreover, the accuracy of the assistive cane can be heavily degraded if the cane is not properly held by the user. To restrict the user to hold the cane in only required orientation an alignment sensing switch is also proposed, which is missing in the current available literature.

This paper aims to study the influence of different reinforcement methods on crack monitoring characteristics of eddy current array sensors, and the sensors with two different reinforcement methods, SUS304 reinforcement and permalloy reinforcement, are proposed.

First, the finite element model of the sensor is established to analyze the influence of the reinforcement plate’s electromagnetic parameters on the crack identification sensitivity. Then, the crack monitoring accuracy test of sensors with two reinforcement methods is carried out. Finally, the fatigue crack monitoring experiments with bolt tightening torques of 45 and 63 N · m are carried out, respectively.

In this study, it is found that the crack identification sensitivity of the sensor can be improved by increasing the relative permeability of the reinforcement plate. The crack monitoring accuracy of the sensors with two different reinforcement methods is about 1 mm. And the crack identification sensitivity of the sensor reinforced by permalloy reinforcement plate is significantly higher than that of the sensor reinforced by SUS304 reinforcement plate.

The sensor reinforced by reinforcement plate can work normally under the squeezing action of the bolt, and the crack monitoring sensitivity of the sensor can be significantly improved by using the reinforcement plate with high relative permeability.

A number of techniques are described for determining the thickness of glass sheets during their manufacture.