查看更多>>摘要：? 2022 Elsevier LtdFault detection and diagnosis in time series data are becoming mainstream in most industrial applications since the increase of monitoring sensors in machinery. Traditional methods generally require pre-processing techniques before training; however, this task becomes very time-consuming with multiple sensors. Recently, deep learning methods have shown great results on time series data. This paper proposes a multi-head 1D Convolution Neural Network (1D CNN) to detect and diagnose six different types of faults in an electric motor using two accelerometers measuring in two different directions. This architecture was chosen due to each head can deal with each sensor individually, increasing feature extraction. The proposed method is verified through a series of experiments with seven different induced faults and operation conditions. The results show that the proposed architecture is very accurate for multi-sensor fault detection using vibration time series. Since the experiments are based on real electric motors and faults, these results are promising in real applications.
查看更多>>摘要：? 2022 Elsevier LtdIn environments such as urban canyons and indoor environments, an insufficient number of visible satellites can degrade the positioning performance of the BeiDou Navigation Satellite System (BDS). Thus, a positioning algorithm that combines the BDS and 5G technology was developed based on raw observation data. Three different satellite occlusion environments were simulated to compare the effects of factors such as the number of base stations and geometric configurations on the positioning performance. The experimental results revealed that the introduction of 5G base stations effectively increased the positioning accuracy and reliability under different occlusion conditions. Additionally, increasing the number of base stations and optimizing the geometric configuration further improved the accuracy and reliability of fusion localization. Moreover, the positive effects of the introduction of 5G base stations were stronger under more severe satellite occlusion conditions. In the future, this fusion positioning algorithm is expected to facilitate the realization of seamless indoor and outdoor positioning.
查看更多>>摘要：? 2022 Elsevier LtdA prototype of the linear standing-wave ultrasonic motors having arc tip is designed and manufactured, and the output performances and mechanical characteristics were tested and evaluated using a home-made measured simple system in this study. Results show that the flexible design of the driving foot is interesting for the performance improvement and simplification design of standing-wave ultrasonic motors. The measured system is simple and is available to evaluate the output performances (thrust and speed) and mechanical characteristics curves of linear motors. The influence trend of preload and driving voltage on output speed is opposite, while the influence trend of thrust is parabola. The peak value of applied voltage is critical for the mechanical characteristic curve of piezoelectric motor. This study also supports a basic measurement approach for service performances of linear ultrasonic motors and the tribological behaviors of motor and/or actuator devices using piezoelectric vibration.
查看更多>>摘要：? 2022Accurate modeling of friction in a roller linear motion guide (RLMG) bears significance in the positional deviation compensation of heavy-load mechanical systems. However, few models can predict the friction fluctuations performance of the RLMG. To address this problem, we propose a calculation method for calculating the time-varying friction based on a new five degree-of-freedom (5-DOF) dynamic stiffness model. In this approach, the rolling contact mechanism between the roller and raceway is analyzed. A new 5-DOF dynamic stiffness model is derived by considering the roller pitch shift, working phase and nonlinear friction damping, which is iteratively solved by four-order Runge-Kutta method under computing the initial value of each iteration. Based on this, the time-varying contact load of each roller under the periodic variations of roller-contact positions is calculated. Then, a time-varying friction calculation model is formulated considering the combined effect of the time-varying contact load, contact area and lubrication viscosity variations between the roller and raceway. The effects of the load magnitude, load orientation, roller pitch shift, preload and velocity on the 5-DOF real-time displacement, time-varying contact load and time-varying friction are discussed. The experimental results demonstrate the superiority of the proposed approach compared to the traditional model.
查看更多>>摘要：? 2022 Elsevier LtdThis study focused on the monitoring of a biogas digester (BD) for treatment of food waste using an e-nose system. The e-nose system along with Principal Component Analysis (PCA) were applied to monitor the gaseous headspace of a mesophilic BD. In this method the digester was allowed to feed based on monitoring indices, i.e. “recovery time” and “position of sensors”, using e-nose data analysis. The results showed that the digester can be kept under the steady-state condition and good performance during evaluation phase, as organic acids to total alkalinity (FOS/TAC) was 0.2–0.3, pH was stabilized near to 8, the mean of volatile solids reduction and the daily methane production rate were 82% and 1.24 Nm3/m3 d, respectively. This study presents a robust monitoring of BD based on an adaptable reference point and graphical monitoring on plots of PCA that make it more flexible than the classical parameter monitoring with determined threshold.
查看更多>>摘要：? 2022 Elsevier LtdThe dry electrode for biopotential recording is urgently need in wearable health monitoring systems, brain-computer interface (BCI), and human–computer interaction (HCI). However, high contact impedances of the electrode and the skin and inadequate shape adaptability of the electrode are challenges for the dry electrode to record signals accurately. Here, we present a flexible dry electrode based on transferring MXene (Ti3C2Tx) ink on a flexible polyimide (PI) substrate for biopotential recording. The electrode exhibits low contact impedances and excellent flexibility to conform the skin well. In vivo biopotential recording demonstrated the flexible dry electrode can record electrocardiograms (ECG), electroencephalograms (EEG), and electrooculogram (EOG) as accurately as the standard electrode (Ag/AgCl electrode). Moreover, our electrode can record ECG accurately, even the subject is in motion. The flexible dry electrode is suitable for wearable biopotential recording and promising to be used in wearable health monitoring systems, BCI, and HCI.
查看更多>>摘要：? 2022 Elsevier LtdThe calibration accuracy of the inertial navigation system (INS) has a non-negligible effect on its actual navigation performance. As the core component of the INS, the scale factor error of the fiber optical gyroscope (FOG) is one of the main error sources of the INS, which has a vital impact on the navigation accuracy. Generally, the scale factor of FOG is considered to be a constant value, but with the increasing demand for the accuracy of FOG, the scale factor error can not be ignored, how to calibration the FOG scale factor at different input velocity rates and temperature has attracted people's attention. The traditional calibration methods usually select several fixed temperature points and input velocity points, then the scale factor error is compensated by linear fitting or piecewise fitting. In order to improve the calibration accuracy, our paper considers the coupling effect of input velocity rate and temperature and designs a calibration experiment at continuous input velocity rates and temperature, the calibration time is shortened by 30%, then we propose a nonlinear error compensation method based on the LSTM. The experimental result shows that the std error of the FOG scale factor is reduced from 280 ppm to 13 ppm and the angle measurement error is reduced by 70%, which verify the effectiveness of our method.
查看更多>>摘要：? 2022 Elsevier LtdConsidering the recent use of three-dimensional digitalization equipment in ballistic vest tests to characterize trauma caused by projectiles, this study carried out a performance analysis of a 3D structured light scanner to measure trauma depths. Artifacts were manufactured and digitized by a 3D scanner and by an articulated arm coordinate measuring machine, which provided the reference values. A process was developed for estimating the depth from the point clouds, one of the main contributions of this work. Filtering and segmentation of the point clouds allowed the extraction of the trauma depths for later comparison. The systematic errors reported in the literature for structured light scanning equipment were confirmed, and it was statistically verified that the critical trauma measurement values are correctly measured, with a bias of 0.11 mm and standard measurement uncertainty of 0.12 mm. Finally, a real ballistic vest test shows the applicability in a practical scenario.
查看更多>>摘要：? 2022Aiming at the problems of accuracy, non-real-time performance, poor reliability and high complexity in belt conveyor longitudinal tearing detection, a belt conveyor longitudinal tearing detection method based on sound is proposed. The sound signals of belt conveyors are collected using a sound acquisition processor. First, the sound signal is processed by a preprocessing algorithm. The characteristics of the processed sound signal are extracted using the LFCC and GFCC combined with a feature extraction algorithm. The feature data of the sound signal are divided into a training set and a test set. The parameters of the convolutional neural network are improved by training and optimization of the training set data. Finally, a convolutional neural network model of the sound signal characteristics of a belt conveyor is obtained. The model is used to classify and identify the longitudinal tearing sound signals of the test set. The experimental results show that this method can realize the identification and detection of the longitudinal tearing sound of a belt conveyor. The average accuracy of the detection is above 94%, and the average processing time is 21.6 ms. The detection range is large, the cost is low, and the accuracy, real-time performance and reliability are high, which meets the requirements of longitudinal tear detection.
查看更多>>摘要：? 2022 Elsevier LtdHoning groove features of a cylinder liner surface contain helpful information on surface performance. Traditional honing surface evaluation methods do not focus on groove features, which is significant to surface functions. Hence, a topographical feature segmentation algorithm and corresponding evaluation parameters are needed. This paper proposes an improved level-set-based segmentation algorithm for groove feature extraction. The proposed algorithm was tested on a real honing surface dataset compared to some state-of-art algorithms, including the classical height thresholding and watershed segmentation. The results show that the proposed method is robust against initial conditions and improves both segmentation accuracy and computational speed. Specifically, a 30% accuracy improvement over the best-tested level-set algorithm has been observed. Another case study on fold-mental characterization was conducted, which also validated the accuracy and speed performance of the proposed algorithm.
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