Search Results (585)

The article deals with the further development of national innovative subway cars with asynchronous electric drives and energy recovery systems through the introduction of capacitive energy storage. It has been determined that the assessment of the effectiveness of existing concepts for energy processes control of subway cars with asynchronous electric drives and capacitive energy storage under identical specified conditions remains a relevant issue. Five of the most promising concepts for managing energy processes were selected and idealized. Oscillograms of energy flows for the selected concepts are presented. Parameters for evaluating the effectiveness of the selected control concepts are presented. The scientific novelty lies in the development of a procedure for selecting a rational concept for controlling energy processes in subway rolling stock with asynchronous electric drives and CES, based on the application of a unified comparative analysis system using a comprehensive evaluation criterion. A scheme for replacing subway cars with asynchronous electric drives and capacitive energy storage is presented, and a mathematical model of energy flow processes for traction and regenerative braking modes has been developed based on this scheme. Algorithms for controlling energy processes between asynchronous electric drives, capacitive energy storage devices, and contact networks have been developed for each of the selected concepts. The efficiency of each of the five selected concepts for the same specified operating conditions of the subway cars, parameters of the asynchronous traction electric drive and capacitive energy storage device has been investigated using the developed mathematical model and the formulated comprehensive evaluation criterion. It was established that it is possible to save up to 18% of the electricity consumed from the contact network per braking-acceleration cycle under the specified operating conditions, parameters of the subway cars, asynchronous traction electric drive, and capacitive energy storage device. An additional possibility exists to reduce the installed power of the power supply system equipment by up to 33.5% under the specified operating conditions of a subway train with the proposed technical characteristics. It has been determined that the most rational concept for controlling energy processes in subway cars with asynchronous electric drives and capacitive energy storage is the fifth concept, which allows the use of stored energy from regenerative braking in both normal and emergency operation of the subway power supply system. Full article

To mitigate driving risks from brake failure on long and steep downhill sections, this study designs three deployment schemes for radar–video fusion devices: a baseline scenario with no coverage, a scenario with partial coverage in high-risk areas, and a scenario with full coverage. Corresponding information service strategies are delivered via Human–Machine Interfaces (HMIs), forming an integrated active prevention and control framework from risk perception to preventive action. Driving simulation experiments focusing on the car-following process were conducted to collect vehicle operational data and extract characteristic indicators based on the Wiedemann model. A Generalized Linear Mixed Model was employed to comprehensively examine the effects of HMIs on car-following behavior to identify the optimal active prevention strategy. Results show that drivers exhibit greater caution under the partial coverage scheme, with time headway increasing by 47.63% compared to the scheme with no radar–video fusion devices to ensure safety. Under full coverage conditions, drivers can obtain real-time information about the leading vehicle’s status and the distance between the two vehicles in key risk sections. Drivers choose to follow the leading vehicle, balancing both safety in car-following and efficiency on long and steep downhill sections. As the level of accompanying services improves, drivers engage in self-regulation to avoid rear-end collisions. Particularly under the scheme with full coverage of radar–video fusion devices, the standing distance significantly increases by 219.37% compared to the partial coverage condition. Drivers demonstrate optimal vehicle control capabilities. Furthermore, there is an interaction effect between the accompanying service strategy and drivers’ attributes on car-following behaviors. Under different schemes, more experienced drivers exhibit a certain degree of aggressiveness, providing a basis for the targeted design of information services for different types of drivers. The findings support the deployment and application of risk perception and prevention devices on long and steep downhill sections, which can effectively enhance the comprehensive safety of such special roads in the connected vehicle environment. Full article

This study investigated the relationship between the surface microstructure of pearlite steel wheels and the formation of fatigue cracks during the braking process by using a full-size wheel braking test rig. After fatigue failure, the surface microstructural evolution and fatigue crack initiation and propagation of the wheel sample were systematically analyzed by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results showed that after braking of 1572 cycles, a large number of fatigue cracks formed at the wheel tread, which caused the wheel to break. After fatigue failure, some dark areas formed at the wheel tread, which were composed of Fe₃O₄ compounds. This indicates that severe oxidation was produced at the wheel tread during braking due to the high temperature. After fatigue failure, a continuous thermal white etching layer (T-WEL) was formed in some areas of the wheel tread, while crescent-shaped T-WEL was found in other areas. The microstructure of the T-WEL was composed of martensite phase. The rapid increase and decrease in temperature at the wheel tread during the braking process caused martensitic transformation at the wheel tread. The hardness of the sample reached to about 900 HV in WEL and it reduced with the increase in distance from the surface. The cracks were initiated from the surface and gradually propagated into the matrix. However, the crack propagation mode in the continuous T-WEL and crescent-shaped T-WEL was different. In the continuous T-WEL, the continuous T-WEL of the wheel can be peeled off during the braking wear process, and then the crack was gradually propagated into the matrix in the T-WEL peeled area. As for the crescent-shaped T-WEL, due to the large hardness difference between T-WEL and pearlite, the crack initiated at the interface between the T-WEL and pearlite and gradually propagated into the matrix. Full article

This study investigates the effect of waste cement dust (CD) and rock wool (RW) inorganic fiber on the tribological performance of brake friction composite materials. Five formulations were fabricated by varying CD from 65 to 45 wt.% and RW from 5 to 25 wt.% and evaluated for tribological properties on a Chase friction testing machine in accordance with IS 2742 test procedures. The results show that composites containing higher CD and lower RW exhibited higher coefficients of friction, lower friction variability, and improved fade resistance. In contrast, composites containing higher RW and lower CD showed improved recovery characteristics and substantially enhanced wear resistance. The performance coefficient of friction decreased from about 0.521 to 0.442 as the formulation shifted from CD-rich to RW-rich compositions, while the variability coefficient increased from about 0.364 to 0.516. The highest wear was recorded for the composite containing 65 wt.% CD and 5 wt.% RW inorganic fiber, whereas the lowest friction fluctuations were obtained for the composite containing 55 wt.% CD and 15 wt.% RW inorganic fiber. Finally, a simple ranking process-based decision-making technique was employed to evaluate the overall performance of all the composites, suggesting 55 wt.% CD as the optimal content. These findings confirm the potential of waste CD as a viable functional constituent in brake friction composites when combined with RW inorganic fiber in an optimized manner. Full article

Train brake systems are characterized by strong friction and open-system features during the service process. Low environmental temperatures significantly affect the contact interface and the attrition characteristics of the braking frictional couple, thus intensifying friction-induced vibration and threatening operational safety. To elucidate the impact of environmental temperature on the frictional vibration characteristics of train brake systems, braking deceleration tests under different environmental temperatures were first conducted to obtain the evolution of vibration, noise, and friction coefficient with environmental temperature and brake disc rotational speed. Then, the Stribeck friction parameters under different environmental temperatures were identified using a genetic algorithm. On this basis, a brake system dynamic model was developed, incorporating disc–pad friction, wheel–rail adhesion, and the relative torsion between the brake disc and the wheelset, enabling accurate examination of the vibrational behaviour arising from friction under different environmental temperatures. And the dynamic relationship among environmental temperature, interface friction parameters, and vibration characteristics of the brake system during braking deceleration was elucidated. The findings indicate that as the environmental temperature decreases, the dynamic friction coefficient increases during the relatively high-speed braking phase, intensifying high-frequency unstable vibrations of the braking assembly. During the relatively low-speed braking phase, the friction coefficient exhibits an obvious negative-slope relationship with vehicle speed that means the friction coefficient increases as the speed decreases, and this negative slope effect is enhanced under low-temperature conditions. Consequently, it triggers intense stick–slip motion at the disc–pad interface and even severe vibrations of various components in the brake system, leading to a sudden increase in vibration intensity in the relatively low-speed range. Full article

A pipeline intelligent plugging robot (PIPR) is an important tool in subsea pipeline maintenance and emergency repair. Precise position-tracking control is crucial for the in-pipe plugging operation of a PIPR. The anchoring module is the key component responsible for fixed-point braking, which faces the challenges of insufficient structural adaptability within a narrow space. Additionally, traditional PID control may lead to poor robustness under fluctuating working conditions and load disturbances. To address these issues, this study designs a novel anchoring module combining screw transmission, an eccentric crank–slider mechanism, and a parallelogram linkage. To achieve adaptive tracking control, the improved deep deterministic policy gradient (DDPG) algorithm is introduced to optimize the parameters of the PID controller. A reward function with mechanical constraint penalties and a dual-phase strategy is proposed for dynamic parameter optimization. All control performances are analyzed and verified through simulations. The results indicate that the proposed method outperforms traditional PID control as regards response speed, overshoot, and robustness, which can achieve precise anchoring. This study provides a theoretical foundation for ensuring the precision of the plugging process. Full article

The brake–release stability of electro-hydraulic thrusters (EHTs) significantly affects the safety of hydraulic braking systems, especially under low-temperature conditions with varying fluid viscosity. Most existing studies have focused on macroscopic braking characteristics, while the internal flow field variation and vortex evolution mechanism during the brake–release process remain insufficiently explored. In this work, transient CFD simulations are conducted to investigate vortex formation rules and flow field characteristics inside an EHT. Three typical vortex structures denoted as α, β, and γ are identified, and the independent and coupling influences of fluid dynamic viscosity and motor speed on vortex intensity and piston-bottom pressure are quantitatively analyzed. The results show that vortices α and β trigger flow disorder and additional hydraulic energy loss, while vortex γ optimizes flow uniformity and assists piston extension. Higher fluid viscosity exacerbates vortex development and pressure fluctuation, while increasing motor speed accelerates transient flow field evolution. This study clarifies the internal flow mechanism of EHT brake–release behavior and provides reliable parametric guidance for optimizing the low-temperature performance of electro-hydraulic braking systems. Full article

Adipose tissue (AT) browning is an inducible cellular phenomenon that promotes lipid oxidation to increase energy expenditure, reducing adiposity. Various transcription regulators involved in the AT browning process have been reported, but their complex molecular mechanisms remain poorly understood. Here, we explore the effects of SIRT7, one of seven mammalian sirtuins, on AT browning and elucidate the underlying mechanisms. SIRT7 deficiency increased the expression of browning genes in beige adipocytes differentiated from subcutaneous white AT (scWAT) stromal vascular fraction (SVF) cells isolated from adipocyte-specific Sirt7 knockout (Sirt7 AdKO) mice. The effect of SIRT7 on beige adipocyte differentiation was confirmed in Sirt7 knockdown (KD) mouse scWAT and human supraclavicular brown AT (scBAT) SVF cell lines. Mechanistically, SIRT7 deacetylated PPARγ2 (peroxisome proliferator-activated receptor γ2) at lysine (K) 382, thereby attenuating interaction with the transcriptional coactivator PRDM16 (PR domain-containing 16). In differentiated beige adipocytes, the acetylation-mimicking mutant PPARγ2^K382Q had higher transcriptional activity compared with the deacetylation-mimicking mutant PPARγ2^K382R. Furthermore, the interaction between endogenous SIRT7 and PPARγ2 decreased at the onset of beige adipocyte differentiation. Our findings reveal that SIRT7 is an important thermogenic regulator that puts the brake on AT browning by deacetylating PPARγ2. Full article

This paper presents an FPGA-based hardware-in-the-loop (HIL) platform for real-time simulation testing of anti-lock braking system (ABS) electronic control units (ECUs). The proposed system integrates a Temporal Convolutional Network (TCN) model implemented on FPGA hardware to provide real-time predictions of wheel speed sensors under complex braking scenarios. The FPGA acceleration achieves low-latency processing with a total end-to-end latency of 10.61 µs per prediction cycle, corresponding to approximately 94.3 Ksamples/s, which is suitable for closed-loop automotive testing. Experimental results show that the TCN model provides accurate prediction based on mean squared errors below 0.001043 for key parameters such as wheel speed sensors and lateral acceleration. The modular architecture of the simulator allows extensibility to other automotive ECUs and provides a scalable solution for real-time system validation in safety-critical applications. Full article

This paper presents a wearable system based on low-cost inertial sensors for the continuous monitoring of driver motion and behavior under controlled urban driving conditions. The system consists of distributed wearable units placed on the head, neck, and torso, each equipped with an inertial measurement unit (IMU) that measures linear acceleration and angular velocity. The acquired data are processed in real time to characterize the driver’s kinematic response during vehicle operation. The main contribution of this work is the definition of a novel Driving Aggressiveness Index (DAI) for quantitative driving style assessment. The proposed index integrates motion-derived features based on acceleration and angular velocity and combines information from multiple body segments through a normalization and weighting strategy, enabling a compact and interpretable representation of driver behavior. Experimental validation was conducted in an urban driving scenario under controlled traffic-free conditions, including typical maneuvers such as straight driving, braking, roundabout navigation, lane changes, and yielding, performed under both normal and aggressive driving styles. The results demonstrate that the monitoring system captures distinct kinematic patterns and that the proposed index provides a clear and consistent separation between driving behaviors. A data-driven threshold is also defined, enabling the quantitative classification of driving styles. Overall, the proposed approach offers an interpretable, scalable, and real-time solution for driver monitoring, with potential applications in road safety and sustainable mobility. Full article

High friction composite brake shoes containing reinforced steel fibers are now widely used in freight train tread braking systems. With the demand for higher transportation efficiency on railway lines with long steep slopes, it is necessary to explore the braking capabilities of existing general freight train high friction composite brake shoes under continuous braking conditions. In this paper, continuous braking tests at different speed levels were conducted using a friction and wear test rig. Through material characterization and interface damage analysis, it was found that reinforced steel fibers can exist as a contact platform at the brake shoe friction interface. Due to the strip-like morphology and high strength features of steel fibers, even after the steel fiber layer is fragmented, it can still promote the formation of a continuous contact platform with complex material composition on the surface, maintaining the progress of the braking process. For existing general freight train high friction composite brake shoes, at speeds up to 80 km/h, although the friction coefficient decreases to some extent, the wear rate maintains a relatively low range. When the speed increases to 100 km/h, the friction coefficient of the braking interface deteriorates severely, and the wear rate of the brake shoe increases sharply, seriously endangering braking safety. The research results reveal the evolution of wear behavior of high friction composite brake shoes containing reinforced steel fibers at different speed levels, providing theoretical support for exploring the braking capabilities and design optimization of brake shoes. Full article

The demographic shift towards an aging population necessitates innovative solutions for care and mobility support. While commercial quadruped robots like the Unitree Go1 offer dynamic stability, their native following modes often lack the safety margins and predictability required, and they do not consistently follow the user, at times deviating and navigating independently. This paper presents a robust, vision-based, person-following algorithm designed to address these limitations. Utilizing a ZED 2 stereo camera and Robot Operating System (ROS), the system employs a finite state machine to ensure deterministic target tracking. A velocity control strategy partitions the robot’s motion into distinct stability, proportional, and braking zones based on depth data to ensure fluid interaction. The framework was validated on a Unitree Go1 quadruped platform in an outdoor environment involving 90-degree turns to evaluate tracking robustness. By operating in a headless mode, the system achieved a mean processing latency of $66.5\pm 4.3$ ms. Experimental results demonstrated consistent operational stability, 0.0% intrusion into the intimate safety zone, and effective velocity synchronization between $0.47$ and $0.54$ m/s. While this study establishes a robust technical baseline using healthy subjects, it serves as a preliminary development platform; further iterative testing with elderly users in clinical settings is required to move toward deployment. Beyond the evaluated trials, the framework maintained reliable functional performance across various care facility workshops, successfully following the target in all deployment scenarios. These findings establish a stable technical foundation for the future development of robotic walking partners. Full article

PCBN tools are widely used in the machining of ferrous metals. Tool edge preparation is a crucial procedure in the tool preparation process that directly affects tool performance. In this paper, tool chamfer grinding and edge blunting were conducted on the PCBN tool to investigate the effect of material microstructures. In tool chamfer grinding, the PCBN tool with larger particles exhibits a larger chamfer width error and roughness than that of smaller particles, and the PCBN tool with higher Al content exhibits a larger chamfer width error and roughness than that with lower Al content. The optimal tool chamfer grinding speed is 24 m/s for the PCBN tool with larger particles, and 27 m/s for smaller particles. The optimal feed rate is 70 mm/min for both PCBN materials. In edge blunting, PCBN tools with larger particles or lower Al content are more difficult to passivate, and the optimal blunting time is about 30 s for an edge radius of 30 μm. The PCBN tools were prepared using the obtained machining parameters and used in the turning of brake pads. It is found that the PCBN tool with smaller particles exhibits longer life than that of larger particles. Although it exhibits the same wear characteristics, the tool life of the PCBN tool with lower Al content is longer than that of the tool with higher Al content. Full article

Falls in older adults and individuals with balance impairments remain a major concern because they are closely associated with injury, reduced mobility, and loss of independence. This study presents a preclinical proof-of-concept for a cognitive smart walker architecture that combines user-compatible walking assistance with active safety intervention. The system integrates a 2D LiDAR sensor for contactless lower-limb monitoring, a six-degree-of-freedom (6-DOF) force/torque sensor to measure user–walker interaction, and an inertial measurement unit (IMU) for dynamic monitoring, with all data processed in real time on a Raspberry Pi/ROS-based platform. Normal walking assistance is provided through a command-level variable admittance-based controller that converts interaction forces into a smoothed signed duty-cycle command rather than a rigid speed-control signal. Safety decisions are managed by a Hierarchical State Machine (HSM). Early-risk conditions are handled through motor-based dynamic braking, whereas severe physical crises additionally deploy lateral support legs to enlarge the base of support. Within this framework, the system can detect and manage foot entanglement, grip loss, forward fall, vertical collapse, lateral fall, successive crises, and recovery-abort events. In experiments across multiple scenarios, the system correctly detected all 50 crisis cases and did not issue unnecessary interventions in 30 non-crisis cases. These findings show that the proposed architecture can preserve transparent walking assistance during normal gait while providing graded, context-sensitive active safety when risk emerges. Full article

In this study, three-dimensional (3D) and one-dimensional (1D) models of port fuel injection (PFI) hydrogen-oxygen internal combustion engine (H₂-O₂ ICE) were established. Firstly, the experiment of PFI-H₂ ICE was conducted to validate the accuracy of the simulation models. Then the effects of the oxygen equivalence ratio (${\Phi }_{O_2}$) and engine speed in the combustion process were analyzed. Results show that two threshold values in the H₂-O₂ ICE combustion can be deduced. When ${\Phi }_{O_2}$ = 0.20, the combustion process is violent with extremely high temperatures and pressure, called excessively intense combustion. When ${\Phi }_{O_2}$ = 0.10, the flame propagation is slow, suggesting it is difficult to ignite at a smaller oxygen equivalence ratio. Moreover, the influence of engine speed on performance parameters is analyzed in a 1D simulation. Results show that the fluctuation of brake thermal efficiency with engine speed becomes more obvious with the decrease in the oxygen equivalence ratio. Full article