Abstract:Traditional rotor position detection schemes typically mount Hall sensors on the stator or motor base to measure the air-gap magnetic field or permanent magnet leakage. However, armature reaction significantly influences detection accuracy. This study proposes mounting Hall sensors on printed circuit boards (PCBs) external to the rotor of an external rotor permanent magnet synchronous motor (PMSM). With the permanent magnet slightly extending beyond the rotor yoke, rotor position is determined by detecting the magnet’s field, which is minimally influenced by armature reaction. Theoretical and experimental analyses reveal that when two Hall sensors are placed at a 90° interval on the PCB, the fundamental phases of their signals are not orthogonal, resulting in position errors. To resolve this, it is shown that orthogonal fundamental phases are achieved when the sensors are spaced at an interval of 90°?P_r/(P_r+1). The theoretical predictions are validated through ANSYS Maxwell finite element simulations and physical motor experiments, confirming the feasibility of the proposed position detection scheme.

Abstract:AC excitation motors offer advantages such as constant frequency under variable speed and decoupled power in steady-state operation, making them suitable for applications like pumped storage and flywheel energy storage. However, these applications demand rapid emergency braking under high-inertia loads, which traditional mechanical braking strategies fail to meet. This study proposes a flexible braking strategy and parameter optimization method for high-inertia AC excitation motors. First, based on rotor structural characteristics, the strategy connects the rotor to a DC excitation source and the stator to multi-stage resistors, and derives the equivalent braking circuit. Second, a braking parameter optimization model is established, with multi-stage braking resistance, rotor excitation current, and resistor switching speed as variables; motor ratings and resistor power limits serve as constraints; and the shortest braking time is set as the objective. The model is solved using a genetic algorithm. Finally, multi-stage resistance braking results and influencing factors are analyzed via Matlab/Simulink simulations, and a 7 kW AC excitation motor platform is used to verify the simulations. Results show that the proposed multi-stage flexible braking strategy effectively reduces braking time, and optimized parameters achieve minimal braking duration while satisfying system power constraints, balancing braking efficiency and device economy.

Abstract:The performance of the driving circuit is critical for the stable and high-precision operation of micro piezoelectric ultrasonic motors. To meet the low-voltage drive and high-speed operation requirements of a 1 mm micro cylindrical piezoelectric ultrasonic motor, a transformer-inverter booster push-pull driving circuit based on the digital signal processing (DSP) 28335 chip is proposed. The DSP 28335 generates four pulse-width modulation (PWM) signals, which alternately drive four MOSFET switches. The inverter boosts and amplifies the voltage through a transformer, and an LC matching circuit filters the output to produce sinusoidal waves with equal amplitude and 90° phase difference, driving the motor. Detailed hardware and software design analyses are presented. Simulation and experiment results show that the output voltage is adjustable from 0 V to 100 V and the frequency from 15 kHz to 50 kHz. The no-load speed of the motor increases linearly with excitation voltage, reaching 480 r/min at 22 kHz and 50 V, satisfying the driving requirements of the 1mm cylindrical piezoelectric ultrasonic motor.

Abstract:For four-wheel independent drive electric vehicles (4WIDEVs), an adaptive cruise control system integrating active front steering (AFS) and direct yaw-moment control (DYC) is developed. The system employs a dual-layer control architecture: the upper-level controller employs model predictive control (MPC) to track the vehicle’s desired longitudinal force and additional yaw moment, while the lower-level controller utilizes the redundancy of AFS and DYC to optimize the front wheel steering angles and torque distribution across all four wheels. This integrated approach enhances both vehicle stability and energy efficiency. Simulation results indicate that, compared to conventional average torque distribution strategies, the proposed control strategy achieves up to 13.23% energy savings while maintaining stability. The study offers insights into enhancing the overall performance of 4WIDEVs.

Abstract:To overcome the limitations of conventional constant-speed control methods in extreme mountainous conditions, this paper proposes a variable-speed coordinated longitudinal-lateral control strategy based on the coupling characteristics of vehicle dynamics. The strategy adopts a hierarchical control structure. The upper layer develops a steady-state evaluation model to provide decision support for subsequent control layers. The middle layer primarily utilizes a two-level model predictive control (MPC) framework to coordinate potential conflicts among longitudinal four-wheel slip rates, lateral active front steering (AFS) and direct yaw control (DYC), and outputs the total driving torque and yaw moment. The lower layer employs a weighted least squares method to optimally distribute torque based on the vehicle’s operating state. A simulation model is constructed using Simulink and CarSim to evaluate performance under various complex road conditions. Results demonstrate that the proposed strategy significantly improves the driving stability of distributed electric vehicles under variable-speed extreme conditions.

Abstract:Previous studies have indicated that the sudden increase in jacking force and pipe sticking in the Guanjingkou rock pipe jacking project is closely associated with mud cake formation from crushed debris. To address this issue, acidic and alkaline solutions are applied on-site to corrode the mud cake and restore jacking progress. However, during the rainy season, these solutions may be transported backward by rainwater, potentially affecting subsequent pipe sections. To investigate whether the coexistence of karst water and acid and alkaline cleaning solutions influences the frictional characteristics of subsequent pipe sections, this study combines indoor direct shear tests, scanning electron microscopy (SEM), and field monitoring. The frictional characteristics at the pipe-rock interface under different pH conditions and debris mixing scenarios are systematically investigated, and the effects of key factors on the friction coefficient are analyzed. By comparing predictions from the experimental model with field monitoring data, the reliability of the results is verified. The findings provide a theoretical foundation and practical guidance for friction control and pipe sticking mitigation in karst environments.

Abstract:To study the influence of L-shaped flow deflectors on the vortex-induced vibration (VIV) characteristics of steel box girders, a series of 20 test cases was designed. A sectional model wind tunnel test was carried out under a +5° wind attack angle to analyze the VIV response patterns associated with variations in horizontal plate width and vertical plate height. In parallel, computational fluid dynamics (CFD) simulations were performed, and the vortex structures were extracted using the Ω vortex identification method to reveal the underlying VIV evolution mechanism. The results show that increasing the horizontal plate width significantly enhances the suppression of vertical bending VIV, while shifting the VIV lock-in region toward higher wind speeds. In contrast, the vertical plate height strongly influences torsional VIV; larger heights tend to induce torsional vibration in the high wind speed regime. Flow field analysis shows that widening the horizontal plate reduces the spanwise extent of vortex structures, thereby improving flow uniformity. Conversely, increasing the vertical plate height promotes the formation and development of vortex clusters, leading to a more complex flow field. Effective vibration mitigation is achieved only when the vortices generated by the attached components are of a comparable scale to those shed from the main girder, enabling interference with the dominant vortex-shedding process.

Abstract:Gas supply systems are generally not allowed to operate under leakage conditions; pipeline networks with extensive leakage after earthquakes must be shut down immediately for inspection and repair. However, under low seismic intensity or minor pipeline damage, complete shutdown is often impractical due to urban gas demand, and the system may operate under slight leakage conditions. To evaluate the reliability of gas supply networks under such conditions, this study integrates post-earthquake pipeline failure states with a leakage model for buried gas pipelines and establishes a hydraulic analysis model that accounts for leakage. A three-state failure probability model is coupled with Monte Carlo method to randomly generate post-earthquake pipeline failure states. The functional reliability of the gas supply network under specified seismic conditions is then evaluated using a “pressure-driven” hydraulic analysis method, and the service status of user nodes after the earthquake is quantified. Based on this framework, the functional reliability of a low-pressure gas supply network under different seismic intensities is analyzed through 1 000 Monte Carlo simulations. The case study results show that the system maintains high seismic reliability under VI and VII earthquakes, while reliability decreases significantly under VIII earthquakes. These findings provide a scientific basis for prost-earthquake reliability assessment and repair planning of urban gas supply pipeline networks.

Abstract:This study applies machine learning techniques to predict the international roughness index (IRI) of asphalt pavement using structural, performance, environmental, and traffic-related variables. Data were obtained from the long-term pavement performance (LTPP) database and Chinese pavement datasets, with 3 066 asphalt pavement sections (construction number =1) selected for analysis. Model parameters were optimized using cross-validation combined with grid search. Considering the selected factors,three machine learning models,namely artificial neural networks(ANN), support vector machines (SVM), and XGBoost, were employed to predict IRI. Their performance was evaluated using R2, root mean square error (RMSE) and mean absolute error (MAE). The results show that XGBoost achieved the best predictive performance (R2 = 0.96, RMSE=0.08, MAE=0.05). Feature importance analysis based on XGBoost indicates that the initial IRI is the most influential factor. These results show that XGBoost can accurately predict asphalt pavement IRI and provide a reference model for pavement management systems.

Abstract:To solve the problems of large specimen size and high dispersion in fatigue tests used to evaluate the anti-reflection cracking performance of asphalt overlays, an indoor test method based on small-sized composite specimens and CSIC (composite specimen interface cracking) specimens is developed. The effects of three sizes of glass fiber grating and the absence of grating on anti-reflection performance are compared and analyzed through fatigue tests, with three parallel specimens prepared for each condition. To evaluate the precision of the proposed method, an XFEM model is established using ABAQUS finite element software to simulate the cracking process of composite specimens and assess anti-reflection crack performance. The results show that the addition of glass fiber grating significantly improves ant-reflection cracking performance, consistent with trends observed in standard tests. Fatigue tests using CSIC specimens effectively improve test precision and reduce result dispersion. The grid participates integrally in the crack resistance process, and smaller grid sizes provide better anti-reflection performance. The ABAQUS simulation results further verify the feasibility of the proposed evaluation method.