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Journal of Chongqing University of Technology(Natural Science)

Table of Content

    20 November 2023, Volume 37 Issue 10 Previous Issue    Next Issue
    Specially invited articles

    A high accuracy node location algorithm based on fingerprint location algorithm for farmland

    2023, 37 (10):  1-8. 
    Abstract ( 200 )   PDF (2729KB) ( 127 )   Save
    Aiming at the problem that the signal of farmland wireless sensor network (WSN) is susceptible to complex environment and the regional vacancies existing in node localization leads to low localization accuracy,a high-precision farmland node positioning algorithm based on fingerprint positioning is proposed.By collecting farmland network signal data,a K-means clustering fingerprint based on signal and coordinate double ruler is constructed; for data fluctuations caused by environmental factors in open farmland,a nonlinear mapping model between received signal strength (RSSI) and node location is established by XGBoost algorithm,and the received signal strength fingerprint matches the coarse localization node location; according to the distance relationship between the point to be measured and the coarse localization area,the weighted geometric optimization algorithm is introduced to locate the point to be measured twice and indent the positioning area to achieve precise positioning of the node.The experimental results show that the localization error of the research algorithm is less than 1.05 m at 80% quantile,which is more accurate and time-efficient than the comparison algorithm.The algorithm can provide a high-precision basic model for the farmland wireless sensor network positioning system.
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    Vehicle engineering

    Thermal management analysis and improvement of an off-road vehicle engine compartment

    2023, 37 (10):  9-16. 
    Abstract ( 171 )   PDF (5056KB) ( 169 )   Save
    In response to the unsatisfactory performance of the cooling system in the engine compartment of an off-road vehicle,an analysis based on 3D simulation and supplemented by 1D simulation is made to improve the thermal management of the engine compartment.By means of 3D simulation,the flow field and temperature field of the engine compartment are analyzed,and the high temperature heat damage parts in the engine compartment are pointed out.By means of 1D simulation,the outlet water temperature of the engine and the outlet air temperature of the hot end of the intercooler are obtained,and the corresponding ATD value and intercooler constant are calculated.On suchbasis,an improved scheme of adding a deflector is adopted to improve the intercooling constant.The simulation results show that there is obvious heat recirculation in the area above the intercooler in the engine compartment,which causes the intercooler constant to fail to meet the requirements.After installing the deflector,the air intake of the intercooler has increased.Its return flow has been reduced,and in the meantime,the intercooling constant drops to to 21.31 ℃ from 28 ℃.These research results provide technical support for the research and development of this off-road vehicle and help reduce its R&D cycle.
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    Experimental and numerical investigation on aerodynamics characteristics for Formula SAE at corners

    2023, 37 (10):  17-27. 
    Abstract ( 157 )   PDF (4674KB) ( 259 )   Save
    To investigate the aerodynamic characteristics of FSAE cars under corner conditions,a simplified FSAE model is established and the overset mesh method is used to simulate the straight and corner conditions.The Skid Pad road experiment is conducted and verified with numerical simulation.The results show that the aerodynamic force varies significantly in corner conditions,in which the aerodynamic drag increases by 1.5% and the aerodynamic downforce increases by 6.5% compared to a straight condition.The additional aerodynamic moments generated in corners will cause the racing car to understeer.The surface pressure distribution of the body inside and outside the corner is asymmetrical.The existence of roll angle is the main reason for the increase of the lower pressure of the diffuser and underbody.The steering angle of front wheel affects the movement of front wing vortex and result in a loss of downforce of front wing.In Skid Pad experiment,the downforce of real racing car stands at 121.9 N,the error approximately 1.6% compared with the simulation.
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    Study of spectral clustering using bi-directional LSTM autoencoder for driving style recognition

    2023, 37 (10):  28-37. 
    Abstract ( 160 )   PDF (3328KB) ( 207 )   Save
    The recognition of different driving styles has profound implications for driving safety,road design and fuel economy.Considering that driving styles are affected by drivers’ immediate and back-and-forth operations,this paper proposes a bi-directional LSTM autoencoder-based spectral clustering model for driving style recognition,in order to address the influence of driving data temporality on driving style recognition.Firstly,a whale optimization algorithm is used to select features from the real-time data from the driving process.Secondly,an autoencoder-based bi-directional LSTM model is built to obtain the eigenvalues and eigenvectors for spectral embedding.Finally,the driving styles are recognized by spectral clustering.The analysis of the real-time driving data shows the accuracy of the proposed method is higher than that of SOM and LSTM-based spectral clustering.Besides,the proposed method can effectively identify drivers’driving style and reflect their operating strategies with fewer features.
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    Improved end-to-end license plate recognition based on GP-NAS

    2023, 37 (10):  38-46. 
    Abstract ( 165 )   PDF (2168KB) ( 113 )   Save
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    3D pavement reconstruction method based on measured load spectrum

    2023, 37 (10):  47-55. 
    Abstract ( 141 )   PDF (4165KB) ( 182 )   Save
    Given that the pavement roughness is difficult to describe during the 3D pavement reconstruction,a method to reverse the pavement using the measured load spectrum is proposed.On the basis of the establishment of the acquisition method and test system,the actual driving load spectrum of a vehicle is collected,and the 3D pavement reconstructed by taking the straight-line constant speed driving conditions under three typical roads as an example.Based on the BP neural network,the pavement reverse model is established,and the BP neural network is trained and verified by using the output response of the vehicle seven-degree-of-freedom road input vibration model under the standard road input.With the measured and integrated load spectrum as the input,the 2D pavement spectrum is obtained and verified.On this basis,the 3D pavement is reconstructed using the triangular mesh method.The results show that when the inverse pavement is used as an excitation input to the seven-degree-of-freedom pavement input vibration model,the relative error between the output spring acceleration and the measured acceleration is less than 8%,which verifies the validity of the pavement reverse results.It provides a feasible method for 3D pavement reconstruction.
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    Study on factors affecting asymmetric characteristics of radial tire ground contact zone under roll condition

    2023, 37 (10):  56-62. 
    Abstract ( 110 )   PDF (3464KB) ( 146 )   Save
    Due to the asymmetry of tire ground contact characteristics during vehicle roll,it has an important impact on vehicle fuel economy,tire wear,and tire dynamics.Moreover,the ground contact characteristics are very dependent on the shape of the tire contact mark and the accurate distribution of pressure on the mark,while the current calculation model for calculating the pressure value on the ground contact mark when the tire is tilted is not accurate.In response to this issue,this paper establishes a three-dimensional finite element model for 205/55 R16 semi steel radial tire as the research object,studies the factors that affect the accurate acquisition of tire ground contact asymmetry,i.e.,pressure distribution,and builds a two-dimensional ground contact pressure model for the tire under roll conditions.By investigating the influencing factors and laws of pressure distribution under roll conditions,this paper provides a foundation for the intelligent research of tires to accurately obtain the peak adhesion coefficient between tires and pavement under roll conditions.
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    Study on dynamic characteristics of vehicle control moment gyro

    2023, 37 (10):  71-80. 
    Abstract ( 133 )   PDF (4332KB) ( 174 )   Save
    The single-frame control moment gyro is the core component for attitude adjustment of two-wheeled vehicles.Carrying out research on the inherent properties and dynamics of the single-frame control moment gyro structure is an important prerequisite for its high-speed and miniaturization.In view of this,a joint Hypermesh-Ansys simulation and analysis model of the single-frame control moment gyro frame-bearing-rotor system coupling is established based on the finite element method,taking into account the multi-material rotor gyro effect,the support frame flexibility,the radial stiffness of the rotor bearing and other factors.On the basis of this model,the modal variation of the coupled system with inertia speed and the influence of the radial stiffness of the rotor bearing on the critical speed of the system are investigated; the accuracy of the critical speed analysis is verified by studying the unbalanced response of the single-frame control moment gyro rotor under a specific eccentric mass; the vibration characteristics of the frame and rotor of the coupled system are investigated under the steady-state rotor condition.The results show that the first-order inherent frequency of the coupled system decreases with increasing inertia speed,and the first-and second-order critical speeds of the system rotor stand approximately at 6 000 r/min and 11 500 r/min respectively; the sensitivity of the critical speed to the change of the radial stiffness of the rotor bearing is obtained,and a reasonable threshold range of 180～320 kN/mm is given for the radial stiffness of the rotor bearing of the coupled system.The vibration of the single-frame control moment gyro frame and rotor under steady-state conditions is revealed.The research results may provide insight into the engineering application and optimization of the control moment gyro.
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    A target detection algorithm based on camera and LiDAR data fusion

    2023, 37 (10):  81-88. 
    Abstract ( 237 )   PDF (3364KB) ( 244 )   Save
    Environmental perception is an important part of self-driving cars and traffic participants (such as cars,pedestrians,cyclists) are the key detection targets.To solve the problem of low accuracy of lidar-only methods in identifying small targets (such as pedestrians and cyclists) due to the sparsity of point cloud,so combining the advantages of lidar and image in target recognition,a target detection algorithm based on multi-sensor fusion,PointPainting+,is proposed.This algorithm,building upon the framework of the PointPainting algorithm,enhances the semantic segmentation stage by incorporating a strip pooling module.This optimization enables the algorithm to achieve better recognition capabilities for long bar-shaped objects.The experimental results demonstrate that PointPainting+ algorithm,compared to the PointPillars baseline algorithm,exhibits an average accuracy improvement of 9.14% for cyclist detection and 9.71% for pedestrian detection.The detection speed can reach 43 frames per second,which meets the real-time requirement,and this algorithm effectively improves the problem of poor detection of long-distance and small targets such as pedestrians and cyclists due to the sparse point cloud.
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    H-infinity dynamic-observer-based fusion estimation of vehicle sideslip angle

    2023, 37 (10):  89-97. 
    Abstract ( 125 )   PDF (1627KB) ( 90 )   Save
    In this paper,a fusion estimation algorithm based on H-infinity theory and dynamic observer theory is proposed to estimate the center of mass sideslip angle,a key parameter in vehicle control system.The proposed dynamic observer has dynamic variables,which can improve the transient and steady-state performance of the estimation algorithm.By introducing deviation vector,constructing Lyapunov function and combining H-infinity theory,the problem of solving parameters matrix of dynamic observer is transformed into a problem of solving linear matrix inequalities(LMI).Then,a two-degree-of-freedom nonlinear dynamic model is established,which is estimated by the dynamic observer using the side-deflection angle of the centroid as the state variable.Finally,a vehicle centroid angle fusion estimation algorithm model based on H-infinity theory and dynamic observer theory is built in Simulink,and CarSim-Simulink co-simulation was carried out to verify the proposed algorithm.
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    Tire-road friction coefficient estimation algorithm under insufficient excitation conditions

    2023, 37 (10):  98-106. 
    Abstract ( 140 )   PDF (3814KB) ( 238 )   Save
    The convergence speed and estimation accuracy of the pavement adhesion coefficient algorithm are reduced due to the uncertainty of road condition and vehicle state excitation.This paper presents a road adhesion coefficient estimation algorithm based on adaptive strong tracking Kalman filter under fuzzy operating conditions.The fuzzy inference method is used to evaluate the excitation degree of the current vehicle state and output the covariance adjustment factor.A strong tracking factor is introduced to correct the Kalman filter algorithm in real time.By adjusting the covariance of the road adhesion factor,the convergence speed of the estimation algorithm is improved,and the strong tracking factor ensures that the algorithm is robust to disturbances from the road surface uncertainty.The estimation effect of the proposed algorithm is validated by a hardware-in-loop test bench.The experimental results show that the proposed estimation method can quickly converge near the true value under large excitation conditions and reduce the amplitude of the fluctuation of the estimated value under small excitation conditions.Compared with strong tracking KF algorithm and KF algorithm,the proposed algorithm markedly improves the algorithm convergence speed and estimation accuracy.
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    Research on fusion perception algorithm of FSAC racing car

    2023, 37 (10):  107-116. 
    Abstract ( 124 )   PDF (3985KB) ( 108 )   Save
    In this paper,an obstacle detection algorithm based on the fusion of lidar and camera is proposed to address the poor adaptability of single sensor detection environment in the Formula Student Autonomous China (FSAC).Firstly,the laser point cloud is filtered,de-ground and conditional Euclidean clustering to determine the position of the cone barrel; secondly,the YOLOv7 algorithm is employed to detect the image and obtain the color information; finally,the sensor is spatiotemporal aligned,and the second nearest neighbor algorithm is used for matching to obtain the position and color information of cone barrel obstacles.Using FSAC car as the experimental platform,in the dynamic test,compared with the intersection fusion algorithm,the accuracy of the algorithm is improved by 5.52%,the error reduced by 29.47%,and the speed increased by 21.66%.The improved data well meet the accuracy and real-time requirements of detection,better realize the perception task of unmanned cars,and provide a reference for the fusion perception of unmanned vehicles.
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    “Extended Reality (XR) Theory，technology and Application”Special Column

    Multi-view 3D reconstruction combining attention mechanism and path aggregation

    2023, 37 (10):  127-135. 
    Abstract ( 153 )   PDF (3186KB) ( 121 )   Save
    Research on learning-based multi-view 3D reconstruction has achieved significant progress,issues like incomplete feature extraction and poor correlation between cost volume still exist,resulting in low reconstruction accuracy.To address these problems,a cascaded network called PAA-MVSNet is designed.Firstly,inspired by the idea of PANet,a “top-down” feature extraction network is designed to extract features at different scales.These features are then concatenated to reduce feature loss.This module outputs three different-scale feature layers,which are fed into the subsequent network to adaptively adjust the depth values and generate higher-precision depth maps.Additionally,to tackle the poor correlation between cost volume,an improved SE attention module is incorporated to optimize the regularization process of the 3D cost volume.This module enhances reconstruction accuracy and completeness.Experimental results on the DTU dataset and Tanks and Temples dataset demonstrate that PAA-MVSNet achieves generalization
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    Mobile AR target recognition algorithm based on improved Yolov5s

    2023, 37 (10):  146-155. 
    Abstract ( 133 )   PDF (3103KB) ( 210 )   Save
    To address the problems of many parameters and slow recognition speed of existing target recognition models,an improved lightweight target detection algorithm Yolov5s-MCB is proposed.Firstly,MobileNetV3 network is used as the Yolov5s backbone feature extraction network to reduce the number of parameters of the model.In order to fit the nonlinear data better and optimize the model convergence effecter,the MobileNetV3 network frontal ReLU activation function is replaced by Mish activation function to avoid gradient disappearance and gradient explosion.Secondly,the BiFPN feature pyramid structure is added to improve the detection accuracy with an iterative feature fusion method.In addition,the introduction of coordinate attention mechanism allows the model to focus on a wide range of location information to improve the detection performance.In order to optimize the model training rate of convergence,Focal-Loss EIOU is used as the border regression loss function to solve the problem of low-quality samples generating drastic oscillations in loss values.The experimental results show that the algorithm achieves an average recognition accuracy of 90.5% in the VOC dataset,a model size of 7.63 MB,and a detection speed of 99 FPS.Compared with Yolov5s,the proposed algorithm improves the inference speed by 17.85% and reduces the model size by 45.9% while keeping the recognition accuracy unchanged,meeting the requirements of the real-time detection tasks and detection accuracy.And the Yolov5s-MCB model is converted to ONNX model and ported to a cell phone to develop an AR application with target detection function in combination with ARCore SDK.
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    A figure skating action recognition method incorporating graph convolutional networks

    2023, 37 (10):  156-165. 
    Abstract ( 131 )   PDF (2744KB) ( 75 )   Save
    To address the problems of complex action features,incomplete feature extraction and low recognition accuracy of existing action recognition methods in figure skating,a multi-scale spatio-temporal graph convolutional network sharing multibranch features and attention is proposed for action recognition in figure skating.First,the OpenPose algorithm is employed to extract skeletal point data of human motion to eliminate noise interference; second,the attention structure of the channel is improved,and the improved attention mechanism enables the model to extract more comprehensive and critical features; then,the multi-scale spatio-temporal graph convolution network with fused attention mechanism is constructed to extract more complete temporal features; finally,the shared features are extracted and fused into the network to allow the model to share data while mining semantic features.The results show that the recognition accuracy of the FSD-10 dataset with 30 types of figure skating movements is 64.5%.Compared with both ST-GCN and CTR-GCN methods,the algorithm achieves higher accuracy in all cases,indicating its effectiveness in the action recognition in figure skating.
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    Open world object detection based on feature disentanglement

    2023, 37 (10):  166-173. 
    Abstract ( 146 )   PDF (3594KB) ( 205 )   Save
    Open-world object detection is a challenging visual task that bridges the gap between traditional object detection and that in real-world scenarios.Unlike traditional methods confined to a limited set of classes,open-world object detection requires not only the identification and detection of objects from known (seen) classes but also the ability to label and gradually learn objects from unknown (unseen) classes.When traditional object detection techniques are directly applied to open-world scenarios,two major problems often arise:first,they might treat unknown classes as background and ignore them; second,they might misclassify unknown classes as known ones.To tackle these problems,this study proposes the utilization of annealing algorithms to separate features of known and unknown classes,guiding the learning process of the detection model.The introduction of the annealing module leads to an improvement in the accuracy of unknown classes,but a slight decrease in the accuracy of known classes.To address this,an efficient channel attention module is incorporated to enhance the accuracy of known classes.Compared to previous methods,this approach demonstrates superior performance in detecting objects from both known and unknown classes.
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    Machinery and materials

    The effect of baffle length on the flow and cavitation inside a semi spiral suction chamber

    2023, 37 (10):  174-181. 
    Abstract ( 104 )   PDF (4025KB) ( 56 )   Save
    To improve the adverse effect of a semi spiral suction chamber on a double suction centrifugal pump,the effect of baffle length on the flow and cavitation inside the semi spiral suction chamber is investigated.Three types of baffle length are used to compare the hydraulic performance of the semi spiral suction chamber and analyze the impact of the baffle on the performance of the semi spiral suction chamber double suction pump.With the computational flow field software ANSYS CFX,the SST turbulence model and the cavitation model based on the Rayleigh Plesset equation are used to numerically simulate the steady-state three-dimensional turbulent full channel flow in the semi helical suction chamber of a double suction centrifugal pump.The distribution of velocity and pressure changes in the semi spiral suction chamber is calculated,and further research is conducted on the flow pattern before entering the impeller.The calculation results show that at a flow rate of 0.8～1.2 Q,the closer the end of the baffle is to the center of the impeller,while an efficiency change is maintained less than 0.36%,the head gradually increases,with an amplitude of 1.2%～1.6%.At the same time,the flow pattern at the tongue of the non cutting semi spiral suction chamber is improved.After exploring the different effective cavitation margins and their development in the initial stage of cavitation under cavitation,it is found that baffles can lead to an earlier initial stage of cavitation,but the development of cavitation is relatively slow.When the head decreases by 3%,the corresponding critical cavitation margin decreases by 0.3 m.Therefore,increasing the baffle can improve cavitation performance and increase the head while maintaining efficiency,providing assistance for the design of a semi spiral suction chamber.
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    Synchronous performance analysis of shield hydraulic propulsion system with dual-fuzzy-PID control

    2023, 37 (10):  182-189. 
    Abstract ( 97 )   PDF (4411KB) ( 89 )   Save
    Combined with the structural characteristics of the shield hydraulic propulsion system,the shield hydraulic propulsion model is built on the multi-domain simulation platform Dymola.Considering the variability of loads during excavation,a dual-fuzzy-PID controller is designed and compared with the PID shield hydraulic propulsion control model.Based on the analysis results,with the parallel synchronous control and master-slave synchronous control strategies,the displacement and pressure tracking characteristics of the shield hydraulic propulsion system are compared and analyzed.The results show that in the start-up stage,the starting propulsion speed of the dual-fuzzy-PID control model is gentle and stable.When sudden load or speed changes occur,the hydraulic propulsion system under dual-fuzzy-PID control can keep stable control of propulsion speed and pressure.The speed and pressure fluctuations are far less than those of the PID control model,showing a better pressure and speed compound control ability.Through comparisons,the displacement tracking characteristics of the hydraulic propulsion system of the four-zone shield are as follows:when the maximum load changes suddenly,the displacement tracking deviation of the parallel synchronous control is 0.68 mm,and that of the master-slave synchronous control is 0.39 mm,42.6% lower than the previous result.In conclusion,the shield hydraulic propulsion system based on dual-fuzzy-PID control has better displacement tracking performance by adopting master-slave synchronous control strategy,which can improve the synchronous control accuracy of the propulsion system.
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    A small wankel pump integrating the actuation component into the execution structure

    2023, 37 (10):  190-201. 
    Abstract ( 96 )   PDF (6765KB) ( 64 )   Save
    In this paper,a concept for a small Wankel pump integrating the actuation component into the execution structure is proposed.The motor drive component is integrated into the execution structure of the Wankel pump,which not only has the original pumping function but also reduces the number of drive mechanisms to shorten the transmission path and improve the efficiency and performance to promote the miniaturization and integration process of the Wankel pump.The complex curve of cylinder shape line envelope of triangular rotor is replaced by simple circular arc curve and the geometric mathematical model of cylinder shape line and triangular rotor shape line is established to simplify the processing.Through the analysis of the dynamic model of the triangular rotor,the mechanical characteristics of the motor components and the working chamber volume of the Wankel pump,the matching mechanism of the output speed,the output flow and the structural parameters,the input voltage and the magnetic induction intensity is obtained.The high-speed camera is used to observe and analyze the flow field in the working chamber of the pump to verify its pumping function and obtain the flow characteristics of the working chamber fluid in the pump.An experimental platform is built to test the output pumping performance of speed of revolution,flow rate and pressure.The experimental results show that the maximum output flow rate reaches 7.55 L/min and the volumetric efficiency up to 38.47% when the input voltage stands at 18 V and the magnetic induction intensity 23 mT,corresponding to a speed of revolution of 768.86 r/min,an output flow rate of 7.55 L/min and an output pressure amplitude of 7 kPa.The speed of revolution,flow rate and pressure amplitude all increase with the rise of voltage and magnetic induction intensity.
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    Plantar pressure based on airbag insole distributed measurement system

    2023, 37 (10):  202-210. 
    Abstract ( 135 )   PDF (3308KB) ( 83 )   Save
    In order to detect the plantar pressure distribution of human body under static and dynamic conditions,a human plantar pressure distribution measurement system based on airbag structure is built to address the problems of poor wearing comfort,high cost,short life span,poor reliability and large size of existing devices.Firstly,the human walking gait characteristics,foot inversion and plantar pressure characteristics are employed to divide the plantar pressure distribution measurement system into regions; secondly,the thickness of the airbag unit body is simulated and iteratively calculated to design a hemispherical shell structure of the airbag unit body; then the data acquisition part of the plantar pressure distribution system region is designed in hardware; thirdly,the calibration and error analysis of the divided measurement regions are performed; finally,the calibration and error analysis of each measurement area are carried out,and the plantar pressure distribution of human body under static and different gait is measured.The experimental results show that the plantar pressure distribution measurement system has a hysteresis error of 2.8%,a repeatability error of 1.77%,and an average measurement error of 1.91%,which can measure the distribution of plantar pressure under static conditions with high accuracy and can classify the human gait under dynamic conditions.The study may provide a certain scientific basis for gait research,rehabilitation training,and balance assessment.
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    Study on the variation law of axial force during transient switching process of turbocharger

    2023, 37 (10):  211-219. 
    Abstract ( 110 )   PDF (4113KB) ( 152 )   Save
    Aiming at the damage of booster thrust bearing during the switching process of sequential turbocharging system,in order to improve the stability of the supercharger during the switching process,this paper takes a certain type of supercharger as the research object,and builds a three-dimensional model of the supercharger.The grid is divided by Fluent and the flow field of compressor and turbine is numerically simulated.The variation law of axial force of turbocharge under typical switching conditions of sequential turbocharging system is analyzed.The results show that during the switching process of the sequential turbocharging system,the longer the transient switching time,the greater the proportion of the fluctuation time of the axial force.During the switching process,the greater the transient speed change of the supercharger,the smaller the proportion of axial force oscillation and the higher the final axial force.The major factors influencing the axial force change of the supercharger include the gas leakage of the wheel back,the switching time and the speed change.
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    Information and computer science

    A data-free universal adversarial attack via weighted activation maximization

    2023, 37 (10):  220-228. 
    Abstract ( 111 )   PDF (3895KB) ( 92 )   Save
    Adversarial examples generated from adversarial attacks can seriously influence the prediction of convolutional neural networks in image classification tasks.Due to the difficult detection of adversarial samples and their transferability (an adversarial sample can undermine the prediction of models with different architectures),crafting adversarial perturbations and generating adversarial samples are of great importance in detecting model defects.However,existing data-free universal adversarial attacks only maximize the activation values of all the convolutional layers to craft adversarial perturbations without any data,which is practical in real-world applications,but adversarial examples are poor in transferability since the difference of features extracted by different convolutional layers is rarely considered.In this paper,a data-free universal adversarial attack method with Weighted Maximization Activation (WAM) is proposed,which assigns the corresponding weight to each convolution layer and increases the weight of activation value from the shallow convolutional layer that can extract generalized features.Experiments on the ImageNet validation set show that the weighted maximization activation attack performs better than other data-free universal methods.Additionally,the ablation experiment verifies that the universal adversarial perturbation can learn generic features from shallow convolutional layers and achieve better transferability.
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    Local path planning algorithm to overcome visibility constraints under temporary roads

    2023, 37 (10):  239-246. 
    Abstract ( 99 )   PDF (2932KB) ( 158 )   Save
    System safety is the primary premise of autonomous driving related research.The local path planning algorithm makes path planning based on local environmental information to ensure that vehicles can successfully pass through specific areas to avoid obstacles and ensure the safety of autonomous vehicles.In order to solve the problem of curve path planning failure caused by the limited visual range of the camera,based on the original Delaunay triangulation path planning algorithm,unilateral cone bucket translation and curve fitting are added to the curve area to realize local path planning,so as to ensure the driving safety of unmanned vehicles.The experimental results show that the planning success rate in the curve driving process is increased from 36.6% to 92.4%,and the average time of a single pathing is 0.264 ms,which is 13.7% less than the original algorithm.The improved Delaunay triangulation algorithm can improve the path planning success rate when the number of unilateral cone barrels is insufficient.In addition,it improves the timeliness of path planning to a certain extent and ensures the safe driving of unmanned vehicles on curves.
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    Cascaded multi-task deep neural network based algorithm for construction site vehicle entry and exit detection and recognition

    2023, 37 (10):  247-254. 
    Abstract ( 183 )   PDF (2660KB) ( 162 )   Save
    In construction scenarios,the management of incoming and outgoing vehicles involves problems such as the safety of construction site property and inaccurate recognition of contaminated licence plates.In response to these problems,a low-computing power vehicle entry/exit detection,recognition and tracking algorithm is proposed,which significantly reduces the human management cost and realises the intelligent management of vehicles at construction sites.Considering that the tasks of model identification and licence plate recognition at construction sites involve mixed detection of large and small targets,this paper proposes a cascaded multi-task end-to-end neural network framework.Firstly,the YOLO network is used to achieve the detection of vehicles at the construction site and the recognition of vehicle models,and on this basis,the vehicle licence plate localisation and recognition,and vehicle target tracking are achieved at the same time.Licence plate recognition is achieved with the help of lightweight neural network to achieve end-to-end accurate recognition algorithm; target tracking algorithm based on improved DeepSort improves the tracking of all vehicles in and out of the site.For the lack of construction site dataset,based on the existing gate monitoring data,a construction site vehicle detection dataset is constructed to train the multi-task cascade neural network,and the algorithm is further validated on the COCO2017 dataset,and the implementation results show the effectiveness and reliability of the algorithm.
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    Electrical and electronic

    IPOA-BP neural network SOH estimation of lithium batteries

    2023, 37 (10):  255-262. 
    Abstract ( 95 )   PDF (3140KB) ( 126 )   Save
    Lithium battery health status (SOH) is the basis for stable battery operation.Improving the accuracy of SOH estimation of lithium batteries can effectively improve their operational reliability.In order to improve the accuracy of SOH estimation of lithium batteries,an estimation model based on improved Pelican optimization algorithm (POA) combined with back propagation (BP) neural network is built.Firstly,several groups of health factors related to lithium battery SOH are extracted through NASA public data set,and a correlation analysis is made,and health factors with good correlation are selected as model inputs.Then the weights and thresholds of BP neural network are optimized by the improved POA algorithm.Compared with BP neural network,particle swarm optimization algorithm (PSO) combined with BP neural network and POA algorithm combined with BP neural network,the proposed method has a lower root-mean-square error and a higher determination coefficient,and thus possesses more practical application values.
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    Iterative learning analysis of nonlinear parameters for global earthing system

    2023, 37 (10):  263-269. 
    Abstract ( 89 )   PDF (1723KB) ( 60 )   Save
    To analyze the complex transient characteristics in voltage and current observed in global earthing systems (GES) under fast impulses,an iterative learning analyzing methodology (ILAM) is proposed for non-linear parameters (NP).Firstly,the mathematical formulation for analysis of NP in GES under fast impulses is built; then the influence of the pre-and post-ionization resistances on the voltage and current is surveyed and ILAM is established for NP in GES based on the ideology of ILC,where the correction pre-and post-ionization resistances is conducted during the tracking of the field-test voltage and current.In doing so,the non-linear relationship related to the time of pre-and post-ionization resistances is determined.Finally,the established methodology is validated by simulation.Results show that by the method,the maximum relative tracking errors in voltage and current stand at 2.82% and 6.97% respectively after adequate iterations.Thus,it may be utilized to analyze the time-varying NP in GES conditionally.
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    Carbon emission flow analysis of the power system considering photovoltaic uncertainty

    2023, 37 (10):  270-278. 
    Abstract ( 114 )   PDF (1730KB) ( 226 )   Save
    In order to analyze the low-carbon contribution of PV generation to the power system,this paper proposes an analysis method of the influence of PV injection power uncertainty on carbon emission flow of the power system.Firstly,through the output of photovoltaic units and a power model of system nodes,the functional expression of illumination intensity and the total carbon flow rate of the system nodes is established.Secondly,the directed path algorithm is used to calculate the path output distribution factor matrix,and the randomness of the PV output is transferred to a balance unit.Based on the correlation matrix of the carbon flow rate between the unit and the system node branches,the influence factors of the PV injection power on the nodes and branches are calculated,and the uncertain characteristics of the carbon emission flow in the power system under the PV injection power are obtained.Finally,the correctness of the proposed method is verified by the measured illumination intensity and the analysis results of IEEE14-node examples.The node carbon potential,branch carbon flow rate and influence factors of the centralized and distributed access power system of the photovoltaic electric field are calculated,and then the low-carbon contribution of photovoltaic access to the power system is quantitatively analyzed.
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    An acoustic imaging algorithm for planar difference microphone coarray

    2023, 37 (10):  279-287. 
    Abstract ( 112 )   PDF (4877KB) ( 120 )   Save
    Microphone array-based acoustic imaging technology is widely used in noise source localization and other applications.A large number of microphone arrays are typically needed to achieve higher spatial resolution.In this paper,we propose a high-resolution imaging algorithm in the domain of difference coarray of planar microphone arrays is proposed,which aims to decrease the number of microphone arrays employed in the current acoustic imaging systems.By applying the proposed method to a two-dimensional nested array,a uniform rectangular array with a significantly higher degree of freedom can be obtained in the difference coarray domain.Through the new algorithm,a high-resolution acoustic imaging with a relatively small number of microphones is achieved.In comparison to the acoustic imaging technique based on a standard planar array,which needs 81 elements for traditional beamforming,simulation results demonstrate that the proposed method employs 49 elements to realize an even less main lobe width.Additionally,the positioning accuracy of the proposed algorithm is higher at a low signal-to-noise ratio.
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    Energy, power and environment

    Simulation analysis of electricity output changes of nuclear power plant caused by plant area heating

    2023, 37 (10):  297-302. 
    Abstract ( 105 )   PDF (2829KB) ( 104 )   Save
    The heating in northern China mainly relies on coal-fired boilers.The emissions of carbon dioxide during a heating season reach 1 billion tons.The extract steam heating from nuclear power plants instead of traditional coal-fired heating is of great significance for reducing CO2 emissions and achieving carbon peak targets.Through the simulation software,the AP1000 unit steam turbine power generation system loop extraction heating is used to heat a plant area of 104 000 square meters.The heating is accomplished by extracting steam at three major locations:main steam pipes,auxiliary steam pipes and the turbine.The optimal extraction positions are located after a comparison of the electricity output changes under three heating strategies.The simulation results show that the extraction heating through the main steam pipes,the auxiliary steam pipes and the turbine causes the electricity output to decrease by 0.36%,0.19% and 1.17% respectively after heating.A comprehensive comparison of the data suggests the auxiliary steam extraction heating in the plant area has the lowest impact on the power generation of nuclear power plants.
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    Multi-physics coupling modeling and analysis of flow field in PEM electrolyzer

    2023, 37 (10):  303-311. 
    Abstract ( 204 )   PDF (2897KB) ( 205 )   Save
    Proton Exchange Membrane Water Electrolyzer (PEMWE) is becoming one of the mainstream hydrogen production carriers with the characteristics of high flexibility and high current density.PEMWE internal physical structure is complex,and the flow field of different form had obvious effects on the electrochemical properties.Therefore,based on the coupling theory of multiple physical fields such as heat transfer,mass transfer,and electrochemical kinetics,a 3D model of PEMWE single cell was established to study the influence of flow field structure on PEMWE performance.The fluid velocity,material distribution and polarization curve of four kinds of flow field structures were compared and analyzed.The results show that under the same operating conditions,the material flow velocity and pressure distribution in the groove of cascade flow field PEMWE are more uniform,and the electrochemical reaction is more sufficient,while the electrochemical performance of traditional parallel flow field structure is poor.In addition,under the working condition of 80 ℃ and 0.1 MPa,the polarization voltage of cascade flow field PEMWE is lower,and the polarization voltage of single cell is only 1.686 V when the current density is 2 A/cm2.Therefore,compared with the other methods,the cascade flow structure can effectively improve the PEMWE single cell performance.
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    Prediction model and application of NOx emission of SCR denitrification system

    2023, 37 (10):  312-318. 
    Abstract ( 133 )   PDF (2417KB) ( 185 )   Save
    To address the problem of low accuracy of export nitrogen oxides (NOx) prediction model of selective catalytic reduction (SCR) system in coal-fired units,this paper develops a real-time prediction model of outlet concentration based on the long short-term memory (LSTM) neural network algorithm optimized by attention mechanism (AM).In the LSTM model,the multivariable and multi-scale features are extracted from the SCR denitrification operation data of thermal power plant,which lead to the nonlinear relationship between input time series and outlet NOx concentration time series.The AM is further adopted to optimize the weight value of the LSTM hidden layer output series,from which the SCR denitrification system NOx outlet concentration prediction model is finally obtained.Experimental results of the operation data from a domestic 350 MW thermal power unit denitrification device show that the AM-LSTM,which achieves higher prediction accuracy and stronger generalization ability than the RNN and LSTM algorithms,may be further applied to large-scale denitrification scenarios with more parameters.
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    “24th International Conference of Fluid Power and Mechatronic Control Engineering” Special Column

    Effect of crescent micro-texture on tribological properties of metal/rubber sealing pair

    2023, 37 (10):  319-326. 
    Abstract ( 87 )   PDF (3605KB) ( 72 )   Save
    Based on the geometric model of the metal/rubber sealing pair of the electro-hydraulic actuator(EHA) and the theory of fluid lubrication,the numerical theoretical model of the dynamic pressure lubrication of the textured metal/rubber sealing pair is built.By simulation,research is conducted on the effects of texture parameters (area density and distribution angle of the crescent texture) and motion speed on the hydrodynamic lubrication performance of sealing pairs.The results show that:with the increase of the texture area density and distribution angle,the oil film bearing capacity has a tendency to increase first and then decrease.And when the texture density reaches 12.8% and the texture angle 90°,the oil film records its highest bearing capacity while the friction coefficient stands at its lowest point.The relative velocity between the friction pairs has an influence on the friction performance of the sealing pair.along with the increase of the relative velocity,the oil film bearing capacity increases whereas the friction coefficient decreases.The crescent micro-texture can effectively improve the friction performance of the metal/rubber sealing pair,and proper designs of the crescent texture parameters can significantly improve the lubrication performance of the metal/rubber sealing pair and enhance its wear resistance.
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    Application of composite control algorithm in pneumatic driving of microfluidic chips

    2023, 37 (10):  327-333. 
    Abstract ( 104 )   PDF (2313KB) ( 83 )   Save
    A composite control method for actuated chambers of pneumatic microfluidic chips is proposed in this paper.The Bang-Bang,k+PWM and compound control methods are employed to analyze the step input signal.The pressure rise time,steady-state accuracy and pressure pulsation of the actuated chamber of the three closed-loop control methods are investigated and compared by experimental research.The composite control method of Bang-Bang+k+PWM combines the advantages of the Bang-Bang control and the k+PWM control:it reduces the response time of the actuated chamber,improves the steady-state accuracy and significantly reduces pressure fluctuations.
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    Numerical calculation study on sealing performance of cylindrical spiral groove gas film seal

    2023, 37 (10):  334-341. 
    Abstract ( 99 )   PDF (2654KB) ( 129 )   Save
    In order to improve sealing performance of the cylindrical spiral groove model,Fluent software is employed to numerically simulate three models:cylindrical spiral groove,T-groove and slotted groove.Three grooved cylinder air film seals are investigated under three variable working conditions:rotational speed,differential pressure and eccentricity.The results of the study show,under different working conditions and structural parameters,the sealing effect of the spiral groove structure is better than that of the T-groove structure and the slotted structure,and the dynamic pressure effect of the spiral groove structure is superior.Both the rotational speed and pressure difference have a significant influence on the sealing performance of the spiral groove whereas the eccentricity has small impact.When the rotational speed reaches 20 000～30 000 r/min,the pressure difference is 0.4～0.7 MPa,and the eccentricity is approximately 0.5,all the sealing performance parameters of the spiral groove cylinder air film seal reach comparatively satisfactory levels.This study may provide guidance for the future research and optimization of cylinder gas film sealing structures.
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    The Changes of upper airway fluid dynamics in patients with OSAHS before and after treatment with snoring arrestor

    2023, 37 (10):  342-348. 
    Abstract ( 113 )   PDF (2318KB) ( 60 )   Save
    To investigate the therapeutic effect of mandibular protrusive anti-snoring device on obstructive sleep apnea-hypopnea syndrome,a three-dimensional model of the upper airway of OSAHS patients is established based on CT images.Computational fluid dynamics method is employed to simulate the three-dimensional model of the upper airway,analyze the changes of fluid dynamics in the upper airway of OSAHS patients before and after using the anti-snoring device CFD-post is employed to post-process the simulation results.The research results show that the upper airway structures of OSAHS patients change after they wear anti-snoring devices,and the mandibular protrusive anti-snoring device can expand the upper airway volume of OSAHS patients,reduce the air flow rate and pressure in the upper airway,and help the patients to reduce their snoring.
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