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    Research on Autonomous Grasping of a Humanoid Robot Based on Vision
    ZHANG Xuchong, YANG Jun
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (7): 53-61.   DOI: 10.12141/j.issn.1000-565X.230528
    Abstract8009)   HTML20)    PDF(pc) (3170KB)(272)       Save

    With the development of robotics technology, humanoid robots have shown application potential and value in multiple fields. Research on autonomous grasping of humanoid robots based on machine vision aims to improve their grasping adaptability and humanoid actions in natural environments. In terms of machine vision, the Realsense-D435 depth camera was adopted, and the YOLO (You Only Look Once) object detection model was used to achieve target object recognition, spatial positioning, depth map cropping, and target point cloud generation. The object’s posture was obtained based on the registration algorithm (ICP) between the target point cloud and the standard point cloud. The robot head was modeled using the D-H method, and the position and posture of the object were converted from the camera coordinate system to the robot coordinate system. In terms of motion planning, according to the grasping law of the human arm, the grasping process was divided into 9 basic actions: initial position, moving to the pre-grasping position, grasping the object, lifting the object, moving the object, moving to placement position placing the object, retreating position, and returning to the initial position. Corresponding grasping postures were determined for different objects to improve the success rate of grasping. Based on the grasping and placing points obtained visually, the remaining key points were calculated independently, and the spatial arc was used as the grasping trajectory. Through Matlab simulation, the rationality of the end movement trajectory and joint trajectory of the robotic arm during the grasping process was verified. Finally, an object grasping experiment was conducted, and the results showed that the humanoid robot can quickly and accurately recognize and locate different objects in the natural environment, and can successfully grasp and transport them with a success rate of over 80%. And it takes into account the imitation of human nature of the action, verifying the effectiveness of the proposed solution. This study can promote the application and popularization of humanoid robots in human daily life.

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    Travel Carbon Emission Prediction Model Based on Resident Attribute Data
    SU Yuejiang, WEN Huiying, YUAN Minxian, WU Dexin, ZHOU Lulu, QI Weiwei
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (8): 23-33.   DOI: 10.12141/j.issn.1000-565X.230355
    Abstract3138)   HTML7)    PDF(pc) (5415KB)(216)       Save

    It is an important basis for precise formulation of transportation emission reduction measures to accurately analyze the importance of factors influencing residents’ travel mode and the sensitivity of carbon emissions. According to the comprehensive analysis of the influencing factors such as family attributes, personal attributes, travel attributes and environmental attributes of the residents’ travel survey, the prediction model of residents’ travel mode was constructed based on LightGBM (Light Gradient Boosting Machine) and verified. Combined with the travel activity level, the carbon emission coefficient of various energy types, the standard coal coefficient and other parameters, the travel carbon emission prediction model based on the resident attribute data was constructed. Finally, taking Guangzhou as an example, the carbon emission intensity and total amount of residents’ travel mode were predicted, and importance of factors influencing travel mode and sensitivity was analyzed.The results indicate that the carbon emission prediction model constructed based on the attribute data of residents can more accurately predict the carbon emission of various modes of travel, better analyze the importance and sensitivity of the influencing factors of carbon emission, and comprehensively reveal the relationship between travel behavior, travel mode and travel carbon emission. Among them, the distance between the start and the end and the nearest bus station or the distance from the nearest subway station, the cost of self-driving and travel distance are important factors affecting the choice of residents’ travel mode. The competitiveness of subway travel increases significantly with the decrease of distance when the distance between the starting and the end point and the nearest subway station drops by 55%. In the area with high density of bus stops, the distance between the start and the nearest bus station is not sensitive to residents’ travel mode choice. It is the turning point of the residents’ travel mode and carbon emission when the carbon emission cost increases by 400%. After passing the turning point, the car travel mode is difficult to transfer. The carbon emissions fell the fastest, with a maximum reduction of 90.4% when the reduction in travel distance was within 90%.

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    Calculation and Spatial Distribution Characteristics of Carbon Emissions from New Energy Vehicles on Expressways
    WEN Huiying, HE Ziqi, HU Yuqing, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (8): 1-13.   DOI: 10.12141/j.issn.1000-565X.230293
    Abstract2435)   HTML12)    PDF(pc) (25804KB)(223)       Save

    In order to overcome the difficulty in estimating the indirect carbon emissions from new energy vehicles due to the energy consumption in a large-scale expressway network, this paper proposes a new carbon emission calculation method of new energy vehicles based on the toll data in expressway ETC network. Firstly, the traffic flow data of new energy vehicles on expressways were cleansed and processed. Then, according to the distribution of toll gantries, road sections were defined and segmented. On this basis, the energy consumption of different types of new energy vehicles was analyzed. Furthermore, a carbon emission quantification model of new energy vehicles in the operational stage was established. Finally, by taking Guangdong Province as an example, the carbon emissions of new energy vehicles on expressways were calculated, with its spatial distribution characteristics being also analyzed. The results show that (1) Category 1 pure electric passenger cars are the main source of carbon emissions from new energy vehicles on expressways, accounting for 74.20% of the total carbon emissions of new energy vehicles, followed by Category 1 pure electric trucks, whose carbon emissions account for 14.18% of the total, and Category 1 plug-in hybrid passenger cars contribute 11.62% of the total; (2) the cities in the Pearl River Delta urban agglomeration are the main contributors to high carbon emissions from new energy vehicles, and the less developed regions in eastern, western and northern Guangdong account for less than 13% of the total carbon emissions from new energy vehicles; (3) the road segments with high carbon emissions from new energy vehicles mainly locate in the transportation hubs and inner-city expressway rings of developed cities, and Guangzhou metropolitan area as well as Shenzhen metropolitan area as the center has a radiating effect on the expressway network of surrounding cities; and (4) in less developed areas, due to the low density of expressway network and relatively lagging infrastructure, the penetration rate of new energy vehicles is low, the corresponding carbon emissions from new energy vehicles are generally low.

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    Experimental Study on Failure Mechanism of RC Frame Structures Based on Performance Design Method
    LING Yuhong, HUANG Qianyi, ZHOU Jing, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (11): 9-20.   DOI: 10.12141/j.issn.1000-565X.230648
    Abstract2150)   HTML0)    PDF(pc) (5218KB)(24)       Save

    To verify the rationality, reliability and fault tolerance of the “two-level and two-stage” seismic performance-based design method of Guangdong standard DBJ/T 15-92—2021 “Technical specification for concrete structures of high-rise buildings”, this study designed two batches of 1∶4 scale plane RC frame structure specimens with the same seismic structure grade of first-level, second-level and third-level. During loading, iron counterweights were arranged on each floor to simulate the distributed load, and the influence of floor and floor load on the failure mechanism of frame structure was considered. The test adopted displacement-controlled single-point loading. The loading point is located at the elevation of the three-story floor beam. Before the longitudinal reinforcement of the column reaches the yield strain, it is single-cycle loading, and after the yield, it is three-cycle loading. Through the pseudo-static test, the seismic failure mode and failure mechanism of the structure were investigated, and the evolution law of seismic performance indexes such as hysteresis curves, ductility, stiffness and energy dissipation was analyzed. The test results show that the plastic hinge development paths of the specimen damage are basically the same, which conforms to the failure mechanism of the plastic hinge ductility mechanism at the beam end. The specimen has no obvious shear failure characteristics, and the bearing capacity utilization coefficient ξ can meet the seismic design requirements of “strong shear and weak bending”. The hysteresis curves of the six frame structure specimens are full, and the seismic ductility coefficient ranges from 4.36 to 6.10. The maximum value range of equivalent viscous damping coefficient is 0.125~0.165, which shows good seismic energy dissipation performance. The floor slab improves the stiffness and bearing capacity of the frame beam, which has a significant impact on the seismic failure mechanism of the specimen. The specimen maintains the seismic failure characteristics of “strong column and weak beam”, and the component importance coefficient η can ensure the seismic design requirements of “strong column and weak beam”. The failure characteristics of the specimens are random, but the overall regularity of the failure mechanism is strong, and the gradient characteristics of the specimens with different seismic structural grades are obvious.

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    A Small Sample Rolling Bearing Fault Diagnosis Method Based on Gramian Angular Difference Field and Generative Adversarial Network
    QIANG Ruiru, ZHAO Xiaoqiang
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (10): 64-75.   DOI: 10.12141/j.issn.1000-565X.240021
    Abstract2013)   HTML13)    PDF(pc) (4151KB)(136)       Save

    Aiming at the problem that deep learning-based rolling bearing fault diagnosis algorithms need to learn from a large amount of labeled data and face poor diagnosis effect when the number of samples is limited, this paper proposed a small-sample rolling bearing fault diagnosis method based on the Gramian angular difference field (GADF) and generative adversarial networks (GAN). Firstly, a data enhancement method based on GADF transform was proposed, and it converts a few 1D vibration signals into 2D GADF images by GADF transform. GADF subgraphs are obtained by cropping to obtain a large number of image samples. Then, a conditional generative adversarial network (CGAN) was combined with Wasserstein GAN with gradient penalty (WGAN-GP) to construct a novel generative adversarial network, which enhances the model training stability by conditional auxiliary information with gradient penalty and designs dynamic coordinate attention mechanism to enhance the spatial perception of the model, so as to generate high-quality samples. Finally, the generative samples were used to train the classifier, and the diagnosis results were obtained on the validation set. Two sets of bearing fault diagnosis experiments in a small sample environment were conducted using the Southeast University dataset and the Case Western Reserve University dataset, respectively. The results show that, compared with traditional generative adversarial networks as well as advanced small-sample fault diagnosis methods, the proposed method can obtain the best results in five fault diagnosis metrics, including accuracy and precision, and can accurately diagnose the type of bearing faults under small-sample conditions.

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    Multi-Task Assisted Driving Policy Learning Method for Autonomous Driving
    LUO Yutao, XUE Zhicheng
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (10): 31-40.   DOI: 10.12141/j.issn.1000-565X.230503
    Abstract1866)   HTML14)    PDF(pc) (3027KB)(212)       Save

    With the development of autonomous driving technology, deep reinforcement learning has become an important means to realize the efficient driving policy learning. However, the implementation of autonomous driving is faced with the challenges brought by the complex and changeable traffic scenes, and the existing deep reinforcement learning methods have the problems of single scene adaptation ability and slow convergence speed. To address these issues and to improve the scene adaptability and policy learning efficiency of autonomous vehicles, this paper proposed a multi-task assisted driving policy learning method. Firstly, this method constructed the encoder-multi-task decoder module based on the deep residual network, squeezing high-dimensional driving scenes into low-dimensional representations, and adopted multi-task-assisted learning of semantic segmentation, depth estimation and speed prediction to improve the scene information richness of low-dimensional representations. Then, the low-dimensional representation was used as the state input to build a decision network based on reinforcement learning, and the multi-constraint reward function was designed to guide the learning of driving strategies. Finally, simulation experiments were conducted in CARLA. The experimental results show that, compared to classic methods such as DDPG and TD3, the proposed method improves the training process through multi-task assistance and learns better driving policies. It achieves higher task success rates and driving scores in several typical urban driving scenarios such as roundabouts and intersections, demonstrating excellent decision-making capabilities and scene adaptability.

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    TsGAN-Based Automatic Generation Algorithm of Lane-Change Cut-in Test Scenarios on Expressways for Autonomous Vehicles
    ZHU Yu, XU Zhigang, ZHAO Xiangmo, WANG Runmin, QU Xiaobo
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (8): 76-88.   DOI: 10.12141/j.issn.1000-565X.230229
    Abstract1835)   HTML7)    PDF(pc) (3981KB)(208)       Save

    The event wherein vehicles from the adjacent lane execute a lane-change maneuver, cutting into the lane occupied by autonomous vehicles, epitomizes a typical high-risk scenario on expressways within the domain of autonomous driving. Replicating such scenarios for testing on actual expressways involves significant safety risks. Virtual simulation test is one of the best approaches to addressing this issue. In order to automatically generate mass high-fidelity expressway lane-change cut-in test scenarios, this paper presents an automatic generation algorithm of lane-change cut-in test scenarios for autonomous vehicles based on TsGAN (Time-Series Generative Adversarial Network). In this algorithm, the time headway and lateral gap at the cut-in moment are taken as the evaluation metrics for scenario risk assessment, and 2 853 instances of lane-change cut-in scenarios with four different risk levels are extracted from the real expressway trajectory dataset highD. A model for generating lane-change cut-in test scenarios is established based on TsGAN, and is trained with the extracted real trajectory data. Then, the model is employed to generate the trajectories for the lane-change vehicle and the tested vehicle before the cut-in moment. To authenticate the generated trajectories, the distribution similarity and spectral error between the generated and the real trajectories are compared. Furthermore, an in-depth analysis of the kinematic interplay between the two vehicles at the cut-in moment and the distribution of trajectory parameters in the generated scenarios is performed to validate the coverage of the generated scenarios within naturalistic settings. The findings can be summarized as follows: (1) as illustrated by the distribution of key trajectory parameters, the average similarity between the generated and the real lane-change trajectories is 79.7%, with an average spectral error less than 8%, and more than 83.2% of the generated trajectories are within the buffer of the most analogous real trajectories, indicating a notable fidelity of the generated trajectories; (2) as compared with the collected real scenarios, the generated instances exhibit a more expansive coverage and a more even distribution within parameter intervals, and the time headway and lateral gap between the lane-change vehicle and the tested vehicle at the cut-in moment decrease by 17.83% and 16.37% in average, respectively, the distribution range of trajectory parameters expands by 19.44%, signifying a heightened coverage of the generated scenarios; and (3) the proposed TsGAN-based generation model has the capability of emulating lane-change cut-in test scenarios with four different risk levels, exhibiting pronounced specificity.

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    Study on Internal Stress of Asphalt Mixture Under Three-Point Bending Mode
    WANG Wei, TAN Yiqiu, XU Yongjiang
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (10): 101-111.   DOI: 10.12141/j.issn.1000-565X.240102
    Abstract1714)   HTML11)    PDF(pc) (5042KB)(114)       Save

    The bending and tensile properties of asphalt mixture affect the service quality and life of asphalt pavement, and its internal stress determines the bending and tensile performance. In order to investigate the internal stress characteristics of asphalt mixtures, this paper adopted the discrete element method to quantitatively evaluate the force chains of each component in asphalt mixtures under the three-point bending mode. Firstly, it constructed a template library of coarse aggregates based on image recognition and realized efficient three-dimensional modeling of asphalt mixture specimen and proposed a three-point bending simulation method. Then the internal force chain distribution of asphalt mixture was visually represented, and data of force chains of each component were extracted. The force chain characteristics were analyzed from the three aspects of composition, strength, and angle. The results show that under the three-point bending mode, the internal force chain field of asphalt mixture exhibits tension and compression zones, and the extrusion of aggregates only takes effect in the compressed zone. 70.8% of the internal contact force of SMA 13 asphalt mixture is provided by the asphalt mortar, and that of AC13 asphalt mixture is 83.2%, indicating that coarse aggregates have little effect under bending and tensile stress and asphalt mortar plays a major role in resisting external loads. The proportion of force chains decrease as the strength increased, and the proportion of strong force chains in the interior of the mortar and the mortar-aggregate interface position is basically the same. The stress between coarse aggregates is uneven, and the mortar plays a significant role in ensuring uniform stress within the asphalt mixture. The strength of horizontal force chains at the aggregate-mortar interface is slightly higher than that in the vertical direction, and the strength of aggregate force chains fluctuates greatly with the change of angle. Asphalt mortar bears the main load during bending and tensile force of asphalt mixture and the research findings can serve as a reference for the structural design and performance evaluation of asphalt mixtures.

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    Study on the Impact Characteristics of Horizontal Curve Elements on Carbon Emissions from Passenger Car Operation
    WANG Xiaofei, LUO Zhen, WANG Shaohua, PAN Ling, ZENG Qiang
    Journal of South China University of Technology(Natural Science Edition)    2025, 53 (2): 68-79.   DOI: 10.12141/j.issn.1000-565X.240047
    Abstract1119)   HTML3)    PDF(pc) (2493KB)(11)       Save

    China’s “14th Five-Year Plan” places higher demands on green transportation development, with emissions from traffic operations being the primary source of carbon emissions in the transportation sector. To investigate the factors influencing carbon emissions of passenger cars on highway curved segments, this study conducted on-site driving tests using OBD-equipped vehicles to collect driving data from typical curved road segments in Guangdong Province, and obtains carbon emission data through the IPCC carbon emission accounting method. Re-levant evaluation indicators influencing passenger car emissions were selected based on road alignment, and gray relational analysis was used to calculate the correlations between these indicators. The results indicate that among the geometric alignment elements of horizontal curve sections, indicators such as the proportion of transition curve length and transition curve parameters are significantly correlated with the segmental carbon emission rate. The radius of the circular curve is also significantly correlated within a specific range. For non-geometric factors, indicators such as the standard deviation and mean of acceleration show significant correlations with carbon emissions, and these two indicators are further associated with geometric factors like transition curve parameters and the proportion of transition curve length. Based on the results of the grey relational analysis, eight correlated indicators were selected, and a grey GM(1, N) model was developed to predict the total carbon emissions of passenger cars on horizontal curve sections. The prediction results show an average relative error of 5.10% compared to the actual values. The predictive performance of the model surpasses that of traditional multiple regression models, demonstrating outstanding performance and reliability in scenarios with limited data.The findings of this study can identify key design and operational parameters significantly influencing carbon emissions, providing a theoretical basis for the low-carbon optimization and management of highway horizontal curve sections.

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    Seismic Performance of Hoop Head Tenon Timber Joint with Added Corner Dampers
    CHEN Qingjun, LEI Jun, LI Bingzhou, ZUO Zhiliang, CAI Jian
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (7): 119-134.   DOI: 10.12141/j.issn.1000-565X.230658
    Abstract1051)   HTML8)    PDF(pc) (12990KB)(113)       Save

    To provide theoretical basis for the restoration of Guangfu wooden structures, five hoop head tenon joint specimens were designed and manufactured using Merbau wood. Considering the influence of the size of mortise and tenon construction, quasi-static tests were carried out on undamaged and unreinforced joint specimens. Then, to preserve the original appearance of the building as much as possible, the damaged joint specimens mentioned above were reinforced by the Queti-type dampers that have minimal influence on the original appearance of the structure. Finally, quasi-static tests were conducted again on the reinforced joints to investigate the difference in their seismic performance and the strengthening effect of the dampers. The results show that the joint specimens reinforced with dampers exhibit significant indentations at the mortise and tenon connections when being loaded to failure. There is noticeable splitting on the outer side of the tenon of the beam and the detachment of the tenon, as well as obvious separation between the rubber and steel plate at the base of the damper. The addition of dampers to joints can compensate the decrease in force-bearing performance caused by initial damage, provide better post-damage stiffness for the damaged mortise and tenon joints, and enhance the ultimate load-bearing capacity and energy absorption capacity. After adding the damper, there occur enhancements in terms of post-damage stiffness, load-bearing capacity and energy absorption of specimens, as compared with the unreinforced joints, with the increment being more than 18%, 19% and 20%, respectively. Moreover, on the basis of the existing simplified mechanical model and in combination with OpenSees, a macro-modelling method was proposed for hoop head tenon timber structures, which helps to obtain hysteresis curves of the joints being in good agreement with the experimental results, meaning that the modelling method can effectively simulate the hysteresis energy dissipation characteristics of the hoop head tenon joints strengthened with dampers.

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    Trajectory Data-Driven Model for Vehicle Lane Change Intention Recognition
    YUAN Renteng, WANG Chenzhu, XIANG Qiaojun, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (6): 34-44.   DOI: 10.12141/j.issn.1000-565X.230258
    Abstract319)   HTML7)    PDF(pc) (2570KB)(49)       Save

    In order to accurately recognize and estimate the lane-changing intentions of vehicles, a vehicle lane change intention recognition model based on TCN-LSTM network is proposed, which combines the temporal processing capability of TCN (Temporal Convolutional Network) with the gate memory mechanism of LSTM (Long Short Term Memory Network). In the investigation, firstly, the driving intentions of the target vehicle are divided into three types, namely going straight, changing lanes to the left, and changing lanes to the right. The running state indicators of the target vehicle and its surrounding neighboring vehicles (including the adjacent front and rear vehicles in the same lane, left lane and right lane) are extracted from the Citysim vehicle trajectory dataset using the median filtering algorithm. Secondly, to overcome the low recognition accuracy, long training time and slow parameter updating existing in statistical theories and traditional machine learning methods, the dilated convolution technique is used to extract the temporal features of time series, and the gate memory units are used to capture the long-term dependency relationships of temporal features. With 54 indicators, including the speed, acceleration, heading angle, heading angle change rate, and relative position information of the target vehicle and surrounding neighboring vehicles, as input parameters, and with the lane change intention of the vehicle as the output indicator, a vehicle lane -change intention recognition model based on the TCN-LSTM network is constructed. Finally, the recognition accuracy of TCN, SVM (Support Vector Machines), LSTM, and TCN-LSTM models under different input time steps are comparatively analyzed. The results show that, when the input time series length is 150 frames, the recognition accuracy of the TCN-LSTM model reaches a maximum of 96.67%; and that, in terms of overall classification accuracy, as compared with LSTM, TCN and SVM models, the TCN-LSTM model improves the classification correctness of lane change intention by 1.34, 0.84 and 2.46 percentage points, respectively, which demonstrates better classification performance.

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    Charging Schedule Optimization of Battery Electric Bus Considering Nonlinear Charging Profile
    XIONG Jie, LAI Kefan, LI Tongfei, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (9): 115-130.   DOI: 10.12141/j.issn.1000-565X.230524
    Abstract256)   HTML15)    PDF(pc) (4868KB)(207)       Save

    Battery electric buses are increasingly applied and promoted in public transportation systems due to their advantages, such as low emissions and low noise levels. However, their limited driving range and long charging time necessitate frequent charging during daily operations, thus leading to a new charging scheduling problem. A reasonable charging schedule is of great significance in reducing the construction cost of charging facilities and charging costs. However, current research on optimizing electric bus charging schedules typically assumes a linear relationship between charging time and state of charge (SOC), and often neglects the comprehensive optimization of charging schedules and charging station operations, resulting in poor scenario reproduction and resource inefficiencies. Therefore, this paper further studied the optimization of charging schedules based on a predefined set of bus trip schedules. A mixed-integer programming model was developed to minimize the total system cost by optimizing the occurrence periods, the start and end times of charging, and the schedules of the charging piles synchronously. The model also fully considers time-of-use electricity pricing policy, partial charging strategies, and the nonlinear characteristics of battery charging. To solve the problem, this paper first linearized the nonlinear charging function of the battery into a piecewise linear one and then used the commercial solver Gurobi to obtain the optimal solution. Additionally, a tailored algorithm was designed based on the minimum-cost-maximum-flow theory and the deficit function. Multiple sets of experiments were conducted to validate the effectiveness of the proposed algorithm based on five bus routes in Beijing. The results, obtained through both Gurobi and the proposed optimized algorithm, demonstrate that the proposed algorithm can achieve a significant reduction in total system costs, ranging from 28.34% to 56.1% across various scenarios. These findings confirm the efficiency of the algorithm and its potential to optimize charging schedules effectively.

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    Study on Evaluation and Influencing Factors of Cognitive Driving Ability in Elderly Drivers
    CHEN Bingshuo, LI Yang, ZHAO Xiaohua, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (9): 142-152.   DOI: 10.12141/j.issn.1000-565X.230579
    Abstract234)   HTML14)    PDF(pc) (2000KB)(232)       Save

    The number of elderly drivers in China continues to grow, and the changes in the driver structure pose challenges to traffic safety. Compared to drivers in other age groups, elderly drivers’ psychological function gradually declines and they are more prone to traffic accidents. Cognitive function is significantly correlated with driving safety performance. Based on the driving characteristics of elderly people, this article started from three cognitive functional areas of attention response ability, executive processing ability, and spatial perception ability, and designed driving simulation experiments to obtain cognitive driving behavior data. It analyzed the differences in driving behavior characteristics among young people, middle-aged people, and elderly people. By combining subjective and objective methods to determine indicator, weights, a method for calculating the cognitive driving behavior index was proposed. A generalized linear mixed model was established with driver attributes and cognitive function as independent variables and cognitive driving behavior index as dependent variable to explore the impact of different factors on cognitive driving ability. The results showed that age, weekly driving frequency, self-regulation, and TMT-B (Trail Making Test-B) were significantly correlated with cognitive driving behavior index, with MMSE (Mini-mental State Examination) showing marginal significant correlation. The cognitive driving behavior index of elderly drivers was greatly influenced by individual traits. Compared to the elderly, the cognitive driving behavior index of young people was worse, while that of middle-aged people was better. People with lower weekly driving frequency had better cognitive driving behavior index than those with higher weekly driving frequency. Drivers with low and medium self-regulation frequencies have better cognitive driving behavior indices than those with high self-regulation frequencies. TMT-B measurement showed that the cognitive driving behavior index of drivers with normal cognition was better than those with cognitive impairment. Starting from the perspective of human factors in traffic accidents, this study explored the cognitive challenges faced by elderly drivers, proposed a calculation method for the cognitive driving behavior index of elderly people, and analyzed the influencing factors, providing reference for simplifying the evaluation process of elderly driving suitability and formulating driving safety intervention strategies.

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    Operational Characteristics and Eco-Safe Influence of Connected Mixed Platoon in Car-Following Event
    FU Qiang, ZHAO Xiaohua, LI Haijian, REN Wenhao, DAI Yibo
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (8): 65-75.   DOI: 10.12141/j.issn.1000-565X.230388
    Abstract229)   HTML7)    PDF(pc) (3935KB)(214)       Save

    Considering the current maturity level of autonomous technology and the general public’s acceptance of this technology, the connected mixed platoon mode may be a practical transitional strategy prior to the widespread deployment of fully autonomous platoons. To study the influence of connected condition and platoon mode on the operational characteristics and eco-safe influence of connected mixed platoon, this paper constructed a connected mixed platoon mode consisting of five vehicles: a human-driven leader vehicle equipped with an L2 connected driving assistance system, followed by connected autonomous vehicles. Thirty-six participants were invited to participate in driving simulation experiments using the developed test platform. Given that time-domain analysis focuses on the variation of indicators in the time dimension, while frequency-domain analysis can explore the frequency distribution characteristics of indicators, this paper analyzed vehicle operation characteristics from the time and frequency domain dimensions with indicators of speed, acceleration, fuel consumption and speed safety entropy. The results show that both the connected condition and the platoon mode contribute to stable vehicle operation and significantly enhance their eco-safety. Compared with the traditional single-vehicle mode, the connected mixed platoon has the best comprehensive efficiency and can reduce the fuel consumption by 10.67% and the speed safety entropy by 73.25%. The research results can provide scheme reference and platform support for autonomous driving enterprises and industries in executing connected HMI design, navigate on autopilot (NOA) development, and the feasibility and effectiveness test of connected mixed platoon.

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    Review of Driving Technology for Permanent Magnet Synchronous Motors Without Electrolytic Capacitor
    WANG Xiaohong, LIANG Yu, PAN Zhifeng, LU Mingqing, LIU Manxi
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (12): 93-108.   DOI: 10.12141/j.issn.1000-565X.240274
    Abstract228)   HTML0)    PDF(pc) (3716KB)(14)       Save

    Due to their small size, low cost and high reliability, permanent magnet synchronous motors have been widely used in the fields of industrial production, transportation and household appliances. Electrolytic capacitor is the middle part of drive system connecting the power grid and the motor. Its life is easily affected by external factors such as environmental temperature and humidity, which seriously restricts the stability and reliability of the motor products. Therefore, the drive system without electrolytic capacitor has become the research hotspot at home and abroad. Scholars have proposed various control strategies for achieving high power factor, suppressing current harmonics, and stabling motor operation. In this paper, the factors affecting the power quality and motor performance of drive system without electrolytic capacitor are analyzed, the advantages and disadvantages of different control strategies are compared, the control strategies for optimizing system performance are summarized, and the driving technology of permanent magnet synchronous motor without electrolytic capacitor is prospected. There comes to the following conclusions: at present, the current power quality is improved mainly through the optimization of motor control algorithm, but the existing methods, such as indirect power control, direct power control, compensation phase current’s non-ideal characteristics and regenerative energy control, all have some limitations; the improvement of motor performance is mainly carried out by the traditional control strategies based on constant bus voltage, such as weak magnetic control and over-modulation, while simultaneously suppressing beat phenomenon and ensuring stable operation of the motor, thus, it is necessary to further consider whether the power factor and current harmonics meet the standards in the subsequent research. Moreover, it is pointed that the comprehensive performance control of non-electrolytic capacitor motor, which takes into account both power quality and motor performance, is the biggest problem faced by the current non-electrolytic capacitor control system. Therefore, it is necessary to carry out a collaborative control for the power grid and the motor to rationally allocate functions and avoid conflicts.

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    Skid Resistance Deterioration and Influencing Factors of Ultra-Thin Wear Layer
    WANG Duanyi, LI Yanbiao, PAN Yanzhu
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (5): 1-9.   DOI: 10.12141/j.issn.1000-565X.220806
    Abstract205)   HTML11)    PDF(pc) (3797KB)(239)       Save

    To accurately evaluate the decay process, mechanism and influencing factors of anti-sliding performance of asphalt ultra-thin wear layer after opening to traffic, this study first used arc mold and its supporting wheel grinding mechanism to prepare arc-shaped ultra-thin wear layer specimens. Then, it carried out the accelerated loading test of asphalt ultra-thin wear layer specimens with four gradation types and three asphalt binder grades by driving wheel accelerated loading system. Finally, it scanned the specimens after a certain number of wheel loads by laser texture scanner. Combined with the test data, the macro and micro structure depth decay models of asphalt ultra-thin wear layer based on S-type function were established respectively, and the independent and coupling effects of each porosity and asphalt binder on skid resistance were analyzed based on grey correlation analysis. The experimental results show that the driving wheel accelerated loading system combined with the S-type function model can quantitatively evaluate and predict the evolution process of the performance of the asphalt ultra-thin wear layer. The porosity affects the early decay rate of the macro and micro structural depth of the ultra-thin wear layer. The larger the porosity, the greater the early decay rate of the macro and micro structural depth of the ultra-thin wear layer. The middle and late decay rate of macro-structure depth is more affected by the grade of asphalt binder. The higher the performance grade of asphalt binder, the slower the decay rate of macrostructure depth in the middle and late stages. Void ratio and asphalt binder grade have similar influence on the decay rate of the micro-structure depth of the ultra-thin wear layer in the middle and late stage. Therefore, when designing the anti-sliding performance of the ultra-thin wear layer, it is beneficial to select the open-graded ultra-thin wear layer mixture with large porosity for the anti-sliding durability of the pavement, and the performance grade of asphalt binder can be reasonably selected according to the traffic volume.

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    Layout Optimization of Static Wireless Charging Facilities for Electric Buses by Considering Battery Degradation Characteristics
    WANG Yongxing, BI Jun, XIE Dongfan, et al
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (6): 45-55.   DOI: 10.12141/j.issn.1000-565X.230359
    Abstract202)   HTML3)    PDF(pc) (1741KB)(186)       Save

    As the existing layout schemes of static wireless charging (SWC) facilities often neglect battery degradation costs, this paper proposes a layout optimization method of SWC facilities for electric buses by considering battery degradation characteristics. Firstly, by considering the operation characteristics of electric buses under opportunity charging mode, a layout optimization method of SWC facilities is developed with simultaneous consideration of charger deployment costs and battery degradation costs, with the function mechanism of battery state of charge (SOC) variety ranges on battery degradation rate being integrated into the model, and with the accumulated energy consumption constraints being introduced in the model to ensure that the SWC layout scheme can satisfy the bus route operation demands. Then, an improved TS (Tabu Search) algorithm is presented to solve the model by overcoming its computational complexity, and the initial solution and neighborhood structure of the algorithm are constructed according to the model characteristics. Finally, a numerical example is designed to verify the model and algorithm. The results indicate that the layout of SWC facilities has significant effects on battery degradation; that the proposed model can reduce 3.8% of the total annualized cost, as compared with the conventional model that neglects the battery degradation characteristics; that the battery degradation cost accounts for up to 72.3% of the total annualized cost under current battery technology and cost conditions; and that the improved TS algorithm is better than the original one because it significantly improves the solution efficiency. Moreover, a sensitive analysis is conducted to explore the impacts of multiple critical factors on optimal results, finding that both the upper bound of battery SOC and the SWC facility charging power have significant negative correlation with the total annualized cost, while the battery’s unit capacity cost, the SWC facility layout cost and the vehicle energy consumption rate all have positive correlation with the total annualized cost in various degrees.

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    Modeling of Source/Drain Access Region Resistance in GaN HEMT Considering Self-Heating and Quasi-Saturation Effect
    YAO Ruohe, YAO Yongkang, GENG Kuiwei
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (7): 1-8.   DOI: 10.12141/j.issn.1000-565X.230405
    Abstract200)   HTML14)    PDF(pc) (2939KB)(228)       Save

    The region between gate and source/drain is called source/drain access region resistances (RD,S) in GaN HEMT equivalent circuit model. Accurately constructing the source/drain access region resistance (RD,S) model is of great significance for analyzing the DC and RF characteristics and building a comprehensive large-signal model for GaN HEMTs. This paper presented an RD,S model considering self-heating and quasi-saturation effects. Firstly, the nonlinear self-heating effect model was derived based on the relationship between the temperature of the source/drain access region (TCH) and the dissipated power (Pdiss). Furthermore, based on the quasi-saturation effect and Trofimenkoff model, a nonlinear RD,S model was constructed. Under low bias conditions, the decrease of 2DEG and mobility with increasing TCH results in the increase of RD,S with TCH at ambient temperatures (Tamb) ranging from 300 to 500 K. At constant Tamb, RD,S presented a nonlinear increasing trend with the increase of bias. The results show that the average relative errors of the RD models in this paper and in the literature are 0.32% and 1.78% respectively, and the root mean square errors (RMSE) are 0.039 and 0.20 Ω respectively. The mean relative errors of RS model are 0.76% and 1.73% respectively, and RMSE are 0.023 and 0.047 Ω respectively. Compared with the experimental data reported in the literature, the results show that the average relative errors of the RD model in this paper and that in the literature are 0.91% and 1.59% respectively, and the RMSE are 0.012 and 0.015 Ω respectively. The mean relative errors of RS are 1.22% and 2.77% respectively, and RMSE were 0.001 5 and 0.003 4 Ω respectively. The proposed model with lower mean relative error and root mean square error, is able to more accurately characterize the variation of RD,S with the drain-source current (IDS) in the linear operating region of GaN HEMTs. This model can be used for the design optimization of the device or as a Spice model for circuit simulation.

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    Coupling Analysis of Rail Transit Stations’ Network Centrality, Ridership and Spatial Heat Map
    WU Jiaorong, CHEN Caiting, DENG Yongqi
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (5): 31-42.   DOI: 10.12141/j.issn.1000-565X.230302
    Abstract200)   HTML13)    PDF(pc) (6507KB)(354)       Save

    Urban spatial heat map reflects population aggregation and street vitality. In order to explore the interactive relationship between urban rail transit and spatial heat map, this study used Baidu heat map and rail transit station ridership data to analyze the coupling characteristics between network centrality, ridership and nearby spatial heat index of rail transit stations on a micro level, taking Shanghai as a case study. Firstly, it investigated the overall coupling relationship between two categories of station attributes and spatial heat through Pearson bivariate correlation analysis. Then, bivariate spatial autocorrelation and geographically weighted regression analysis methods were introduced to explore the spatial association patterns between network centrality and spatial heat, as well as between spatial heat and ridership, followed by a spatial differentiation comparison between the two coupling types. The results show that the coupling relationship between rail network centrality and spatial heat is obviously better than that between ridership and spatial heat at station level, since traffic location advantage can usually develop higher spatial heat, while ridership may be affected by more complex factors. Spatial heat map is more suitable for quantifying the interaction between rail transit and urban space in areas outside the urban core, where increasing rail network centrality has a multiplier effect on spatial heat improvement, but improving spatial heat in areas with low-density development is more conducive to stimulating ridership. It is feasible to evaluate the ridership potential of new stations outside the urban core area by using spatial heat map, but this data alone is not enough to predict ridership. The urban renewal around rail transit stations can be optimized by referring to the differences between the two types of coupling at different spatial locations. This study explored the analytical framework for improving the layout of rail transit network based on urban spatial heat map, and optimizing TOD (Transit-Oriented Development) stations for factors negatively affecting their coupling. It provides a new perspective for measuring the man-land relationship of urban rail transit on the micro level.

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    Taxi Trajectory Characteristics Analysis Based on Frequent Sequence Mining
    LONG Xueqin, WANG Han, WANG Ruixuan
    Journal of South China University of Technology(Natural Science Edition)    2024, 52 (6): 24-33.   DOI: 10.12141/j.issn.1000-565X.230375
    Abstract198)   HTML4)    PDF(pc) (4721KB)(30)       Save

    In order to further clarify the differences in routing behaviors of different taxis, this paper adopted the method of frequent sequence mining to extract the frequent path between the same OD pairs, construct path sets, and analyze the similar characteristics of path sets from static and dynamic perspectives. By taking the trajectory data of taxis in Xi’an City as the research object, the path set between OD pairs is obtained through grid division and road network matching. Then, the frequent path is redefined, the PrefixSpan evolution algorithm is adopted, and the dynamic threshold and frequency index based on the obtained frequent subsequences are introduced to mine frequent paths. Furthermore, in order to complete the construction of three kinds of effective path sets, the shortest path and other paths are extracted, and the general properties of the constructed path sets are analyzed. Finally, the similarity between two-dimension time series (tracks) on the path is represented as dynamic similarity, and the similarity between one-dimension directed sequences (sections) is represented as static similarity, and the similarity analysis of three types of paths is carried out based on the improved longest common subsequence and dynamic time regularity algorithm. The results show that: (1) the similarity between the frequent path and the shortest path is rather high, meaning that most taxis still choose the road with the lowest travel time but not the shortest path; (2) time and distance are still the main considerations for travelers when choosing a path, but travelers do not completely pursue the shortest time or distance; (3) the calculated dynamic similarity is significantly higher than the static similarity, which means that the two-dimension sequential similarity on the path is higher than the one-dimension shape similarity; and (4) the two proposed methods both possess the highest similarity between the frequent path and the shortest path and the lowest similarity between the shortest path and other paths The consistency of the comparison results indicates that the similarity of the static path can be roughly measured by the that of the dynamic trajectory. The proposed frequent path mining algorithm is of certain reliability. It can provide supports for urban traffic managers with recommend routes and planed roads.

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