Braking Force Research Articles

Cooperative optimization of energy recovery and braking feel based on vehicle speed prediction under downshifting conditions

Regenerative braking can effectively recover vehicle kinetic energy, but its energy conversion efficiency is low under low-speed conditions, and there is also the problem of premature exit from energy recovery due to insufficient reverse electromotive force. The cooperation of gearbox gears can increase the speed range for the motor to recover energy, but unreasonable shifting will cause fluctuations in braking force and affect the consistency of the braking feel. Therefore, this paper aims to collaboratively optimize energy recovery and braking force fluctuations during gear shifting. Firstly, based on the model of braking system and transmission, the influence of shift strategy on braking impact and energy recovery is studied. In view of the challenge of determining a shift strategy with uncertain target braking speeds, a speed prediction model reconstructed by the support vector regression (SVR) model and the hybrid nonlinear autoregressive neural network (NAR) is proposed. On the basis of NAR-SVR speed prediction, the coupling effect of braking impact force and energy recovery efficiency is considered, and the collaborative optimization of regenerative braking torque and shift time is solved through a multi-objective cuckoo search algorithm. The hardware-in-the-loop test results verified that under high-speed conditions, the braking energy recovery rate of the proposed strategy was increased by 47.06 %, and the peak braking impact was reduced by 61.4 %. This research can provide a reference for the brake downshift optimization strategy and regenerative braking research of vehicles with non-decoupled electro-hydraulic composite braking systems.

Electronic mechanical braking system executive mechanism design, calculation, and modeling based on dynamic control

Introduction: As science and technology develop, automobiles are moving toward intelligence and electrification and need better braking systems.Methods: To improve the braking system’s response speed and braking effect, a longitudinal dynamics control system for automobiles based on the electronic mechanical braking system was proposed, and the electronic mechanical braking system was improved through automatic disturbance rejection control.Results: The experimental results show that the time required for achieving the target clamping force in the electronic mechanical braking system using self-disturbance rejection control and proportional integral differential control is only 0.01 s, but there is an issue of excessive control in the proportional integral differential system between 0.12 s and 0.2 s, while the self-disturbance rejection controller does not have this problem. Meanwhile, regardless of the interference applied, the electronic mechanical braking system with automatic disturbance rejection control can ensure that the clamping force does not fluctuate. In the joint simulation experiment, the expected acceleration and actual acceleration can remain consistent, and if the expected braking force is 9000 N, then the actual braking force of the electronic mechanical brake (EMB) is also 9000 N.Discussion: The above results indicate that the vehicle longitudinal dynamics control system using the electronic mechanical braking system not only responds fast but also has a good braking effect, avoiding the problem of excessive control and improving the driving experience.

A coupling method for wheel–rail longitudinal interaction

Longitudinal wheel–rail interaction is often neglected in railway engineering research. In order to analyze the system dynamics with consideration of the braking force, a new longitudinal wheel–rail interaction model is proposed in this paper. Then, the reliability of the proposed model is verified by comparing the results obtained from the traditional vehicle-track coupled dynamic model. The calculated dynamic responses of the system with different time steps are compared to illustrate the stability of the proposed method. In the case study, the influence of the track irregularity on the dynamic response of the system is analyzed in detail, and it is found that the influence of the lateral track irregularity on the longitudinal dynamic response of the system is significant. In addition, the effect of the nonlinearity of ballasted bed longitudinal resistance on the longitudinal dynamic response, and it is found that the nonlinear characteristics of the ballast bed cannot be ignored.

RBS and ABS Coordinated Control Strategy Based on Explicit Model Predictive Control.

During the braking process of electric vehicles, both the regenerative braking system (RBS) and anti-lock braking system (ABS) modulate the hydraulic braking force, leading to control conflict that impacts the effectiveness and real-time capability of coordinated control. Aiming to enhance the coordinated control effectiveness of RBS and ABS within the electro-hydraulic composite braking system, this paper proposes a coordinated control strategy based on explicit model predictive control (eMPC-CCS). Initially, a comprehensive braking control framework is established, combining offline adaptive control law generation, online optimized control law application, and state compensation to effectively coordinate braking force through the electro-hydraulic system. During offline processing, eMPC generates a real-time-oriented state feedback control law based on real-world micro trip segments, improving the adaptiveness of the braking strategy across different driving conditions. In the online implementation, the developed three-dimensional eMPC control laws, corresponding to current driving conditions, are invoked, thereby enhancing the potential for real-time braking strategy implementation. Moreover, the state error compensator is integrated into eMPC-CCS, yielding a state gain matrix that optimizes the vehicle braking status and ensures robustness across diverse braking conditions. Lastly, simulation evaluation and hardware-in-the-loop (HIL) testing manifest that the proposed eMPC-CCS effectively coordinates the regenerative and hydraulic braking systems, outperforming other CCSs in terms of braking energy recovery and real-time capability.

From immune equilibrium to tumor ecodynamics.

There is no theory to quantitatively describe the complex tumor ecosystem. At the same time, cancer immunotherapy is considered a revolution in oncology, but the methods used to describe tumors and the criteria used to evaluate efficacy are not keeping pace. The purpose of this study is to establish a new theory for quantitatively describing the tumor ecosystem, innovating the methods of tumor characterization, and establishing new efficacy evaluation criteria for cancer immunotherapy. Based on the mathematization of immune equilibrium theory and the establishment of immunodynamics in a previous study, the method of reverse immunodynamics was used, namely, the immune braking force was regarded as the tumor ecological force and the immune force was regarded as the tumor ecological braking force, and the concept of momentum in physics was applied to the tumor ecosystem to establish a series of tumor ecodynamic equations. These equations were used to solve the fundamental and applied problems of the complex tumor ecosystem. A series of tumor ecodynamic equations were established. The tumor ecological momentum equations and their component factors could be used to distinguish disease progression, pseudoprogression, and hyperprogression in cancer immunotherapy. On this basis, the adjusted tumor momentum equations were established to achieve the equivalence of tumor activity (including immunosuppressive activity and metabolic activity) and tumor volume, which could be used to calculate individual disease remission rate and establish new efficacy evaluation criteria (ieRECIST) for immunotherapy of solid tumor based on tumor ecodynamics. At the same time, the concept of moving cube-to-force square ratio and its expression were proposed to calculate the area under the curve of tumor ecological braking force of blood required to achieve an individual disease remission rate when the adjusted tumor ecological momentum was known. A new theory termed tumor ecodynamics emphasizing both tumor activity and tumor volume is established to solve a series of basic and applied problems in the complex tumor ecosystem. It can be predicted that the future will be the era of cancer immune ecotherapy that targets the entire tumor ecosystem.

Thermal-magnetic coupling inhomogeneous temperature field analysis of cylindrical eddy current brakes

With the increasing requirements for safety and reliability, it is now necessary to analyze the thermal characteristics to the same extent as the electromagnetic design for eddy current brakes(ECB), because the working characteristic will be greatly influenced by temperature. In this paper, the transient thermal-magnetic coupling analysis of permanent magnet cylindrical eddy current brake, which is used as the recoil mechanism in artillery, is presented. First, the structure and working principle of this ECB are described in detail. Second, the analytical electromagnetic model is established by multilayer theory to derive the heat source of this ECB. Thirdly, the thermal-magnetic coupling model is established to calculate the dynamic inhomogeneous temperature field of the ECB. The heat conduction equation is solved in different regions with inhomogeneous internal heat source by Finite Difference method(FDM) in two-dimensional cylindrical coordinate. Finally, the validity of the proposed model is verified by commercial Finite Element software. The thermal characteristic and its effects on braking force is analyzed during working. The maximum value of temperature approximately rises by 16℃ in each firing. The braking force will decline by 8% considering temperature.

Ground Reaction Forces and Energy Exchange During Underwater Walking.

Underwater walking was a crucial step in the evolutionary transition from water to land. Underwater walkers use fins and/or limbs to interact with the benthic substrate and produce propulsive forces. The dynamics of underwater walking remain poorly understood due to the lack of a sufficiently sensitive and waterproof system to measure substrate reaction forces (SRFs). Using an underwater force plate (described in our companion paper), we quantify SRFs during underwater walking in axolotls (Ambystoma mexicanum) and Spot prawn (Pandalus platyceros), synchronized with videography. The horizontal propulsive forces were greater than the braking forces in both species to overcome hydrodynamic drag. In axolotls, potential energy (PE) fluctuations were far smaller than kinetic energy (KE) fluctuations due to high buoyant support (97%), whereas the magnitudes were similar in the prawn due to lower buoyant support (93%). However, both species show minimal evidence of exchange between KE and PE, which, along with the effects of hydrodynamic drag, is incompatible with inverted pendulum dynamics. Our results show that, despite their evolutionary links, underwater walking has fundamentally different dynamics compared with terrestrial walking and emphasize the substantial consequences of differences in body plan in underwater walking.

Structural and dynamic assessment of a friction buffer stop

Under peculiar conditions railway braking system ca fail giving insufficient braking force during train ride or while standstill and buffer stops are used to avoid derailments at the end of railway tracks (dead tracks). Fixed stops are suitable only for quasi-static movements, while absorbing energy stops using hydraulic cylinders, friction shoes clamped on the rail head or a combination of both methods, are installed if crashes at higher speeds (about 25 km/h) are forecasted. Impact forces generated due to the interaction between train and buffer stops require a suitable design of the steel structure which is subjected to stress values depending on the braking performances of the buffer stop itself and a combined structural and dynamic analysis must be carried out to perform a proper design. Due to unavailability of detailed models and the uncertainties of the actual braking performances, the structure of currently available friction buffer stops is heavy and bulky, made of several steel profiles welded or bolted to each other. The paper describes an innovative and optimized design for friction buffer stops focusing on the dynamic analysis performed by Finite Element Method to assess the braking performances and structural strength of the buffer stop.

Walking with unilateral ankle-foot unloading: a comparative biomechanical analysis of three assistive devices

BackgroundFoot and ankle unloading is essential in various clinical contexts, including ulcers, tendon ruptures, and fractures. Choosing the right assistive device is crucial for functionality and recovery. Yet, research on the impact of devices beyond crutches, particularly ankle-foot orthoses (AFOs) designed to unload the ankle and foot, is limited. This study investigates the effects of three types of devices—forearm crutches, knee crutch, and AFO—on biomechanical, metabolic, and subjective parameters during walking with unilateral ankle-foot unloading.MethodsTwenty healthy participants walked at a self-selected speed in four conditions: unassisted able-bodied gait, and using three unloading devices, namely forearm crutches, iWalk knee crutch, and ZeroG AFO. Comprehensive measurements, including motion capture, force plates, and metabolic system, were used to assess various spatiotemporal, kinematic, kinetic, and metabolic parameters. Additionally, participants provided subjective feedback through questionnaires. The conditions were compared using a within-subject crossover study design with repeated measures ANOVA.ResultsSignificant differences were found between the three devices and able-bodied gait. Among the devices, ZeroG exhibited significantly faster walking speed and lower metabolic cost. For the weight-bearing leg, ZeroG exhibited the shortest stance phase, lowest braking forces, and hip and knee angles most similar to normal gait. However, ankle plantarflexion after push-off using ZeroG was most different from normal gait. IWalk and crutches caused significantly larger center-of-mass mediolateral and vertical fluctuations, respectively. Participants rated the ZeroG as the most stable, but more participants complained it caused excessive pressure and pain. Crutches were rated with the highest perceived exertion and lowest comfort, whereas no significant differences between ZeroG and iWalk were found for these parameters.ConclusionsSignificant differences among the devices were identified across all measurements, aligning with previous studies for crutches and iWalk. ZeroG demonstrated favorable performance in most aspects, highlighting the potential of AFOs in enhancing gait rehabilitation when unloading is necessary. However, poor comfort and atypical sound-side ankle kinematics were evident with ZeroG. These findings can assist clinicians in making educated decisions about prescribing ankle-foot unloading devices and guide the design of improved devices that overcome the limitations of existing solutions.

Optimal allocation method of electric/air braking force of high-speed train considering axle load transfer

Reasonable distribution of braking force is a factor for a smooth, safe, and comfortable braking of trains. A dynamic optimal allocation strategy of electric-air braking force is proposed in this paper to solve the problem of the lack of consideration of adhesion difference of train wheelsets in the existing high-speed train electric-air braking force optimal allocation strategies. In this method, the braking strategy gives priority to the use of electric braking force. The force model of a single train in the braking process is analyzed to calculate the change of adhesion between the wheel and rail of each wheelset after axle load transfer, and then the adhesion of the train is estimated in real time. Next, with the goal of maximizing the total adhesion utilization ratio of trailer/motor vehicles, a linear programming distribution function is constructed. The proportional coefficient of adhesion utilization ratio of each train and the application upper limit of braking force in the function is updated according to the change time point of wheelset adhesion. Finally, the braking force is dynamically allocated. The simulation results of Matlab/Simulink show that the proposed algorithm not only uses the different adhesion limits of each trailer to reduce the total amount of braking force undertaken by the motor vehicle, but also considers the adhesion difference of each wheelset. The strategy can effectively reduce the risk and time of motor vehicles during the braking process and improve the stability of the train braking.

Experimental Evaluation of Effect of Leaves on Railroad Tracks in Loss of Braking

This study aims to comprehensively assess the lubrication effect of leaves on wheel–rail contact dynamics using the Virginia Tech-Federal Railroad Administration (VT-FRA) Roller Rig, which closely simulates field conditions with precision and repeatability. Railway operators grapple with the seasonally recurring challenge of leaf contamination, which can cause partial loss of braking and lead to undesired events such as station overruns. Better understanding the adhesion-reducing impact of leaf contamination significantly improves railway engineering practices to counter their effects on train braking and traction. This experimental study evaluates the reduction in traction and braking forces (collectively called “adhesion”) as a function of leaf volume, using two leaf species that commonly grow along U.S. railroad tracks. The test methods rely on the chosen leaves’ transpiration characteristics while ensuring the result’s reproducibility. Leaves were symmetrically positioned on the wheel surface, centered around the mid-rib area within the wear band, and taped on the edges far from the wear band. The critical test parameters (i.e., wheel load, wheel velocity, and percentage creepage) are kept constant among the tests. At the same time, leaf volume is reduced from a maximum amount that covers the entire wheel surface (100% coverage) to no leaves (0%). The latter is used as the baseline. The percentage creepage is kept constant at an exaggerated amount of 2% to accelerate the test time. The results indicate a nonlinear relationship between leaf volume and the loss of braking. Even a small amount of leaf contamination causes a significant reduction in adhesion by as much as 50% compared with no contamination (i.e., baseline). Increasing leaf volume results in contact saturation, beyond which adhesion is not reduced. The minimum adhesion observed in this study is 20% of the maximum adhesion that occurs when no leaf contamination is present.

A Multi-Source Braking Force Control Method for Electric Vehicles Considering Energy Economy

Advancements in electric vehicle technology have promoted the development trend of smart and low-carbon environmental protection. The design and optimization of electric vehicle braking systems faces multiple challenges, including the reasonable allocation and control of braking torque to improve energy economy and braking performance. In this paper, a multi-source braking force system and its control strategy are proposed with the aim of enhancing braking strength, safety, and energy economy during the braking process. Firstly, an ENMPC (explicit nonlinear model predictive control)-based braking force control strategy is proposed to replace the traditional ABS strategy in order to improve braking strength and safety while providing a foundation for the participation of the drive motor in ABS (anti-lock braking system) regulation. Secondly, a grey wolf algorithm is used to rationally allocate mechanical and electrical braking forces, with power consumption as the fitness function, to obtain the optimal allocation method and provide potential for EMB (electro–mechanical brake) optimization. Finally, simulation tests verify that the proposed method can improve braking strength, safety, and energy economy for different road conditions, and compared to other methods, it shows good performance.

Variable Universe Fuzzy-Proportional-Integral-Differential-Based Braking Force Control of Electro-Mechanical Brakes for Mine Underground Electric Trackless Rubber-Tired Vehicles.

Currently, the main solution for braking systems for underground electric trackless rubber-tired vehicles (UETRVs) is traditional hydraulic braking systems, which have the disadvantages of hydraulic pressure crawling, the risk of oil leakage and a high maintenance cost. An electro-mechanical-braking (EMB) system, as a type of novel brake-by-wire (BBW) system, can eliminate the above shortcomings and play a significant role in enhancing the intelligence level of the braking system in order to meet the motion control requirements of unmanned UETRVs. Among these requirements, the accurate control of clamping force is a key technology in controlling performance and the practical implementation of EMB systems. In order to achieve an adaptive clamping force control performance of an EMB system, an optimized fuzzy proportional-integral-differential (PID) controller is proposed, where the improved fuzzy algorithm is utilized to adaptively adjust the gain parameters of classic PID. In order to compensate for the deficiency of single-close-loop control and adjusting the brake gap automatically, a cascaded three-closed-loop control architecture with force/position switch technology is established, where a contact point detection method utilizing motor rotor angle displacement is proposed via experiments. The results of the simulation and experiments indicate that the clamping force response of the proposed multi-close-loop Variable Universe Fuzzy-PID (VUF-PID) controller is faster than the multi-closed-loop Fuzzy-PID and cascaded three-close-loop PID controllers. In addition, the chattering of braking force can be suppressed by 17%. This EMB system may rapidly and automatically finish the operation of the overall braking process, including gap elimination, clamping force tracking and gap recovery, which can obviously enhance the precision of the longitudinal motion control of UETRVs. It can thus serve as a BBW actuator of mine autonomous driving electric vehicles, especially in the stage of braking control.

Comparing the maximal horizontal deceleration demands between a novel acceleration to deceleration assessment and the 505 change of direction test

The importance of quantifying maximal horizontal deceleration performance in athlete populations has received a considerable increase in interest over recent years. However, research is still scarce investigating movement characteristics of maximal horizontal decelerations outside of measures derived from instantaneous horizontal velocity of the centre of mass, using technologies such as radar or laser-based devices. Therefore, this study aimed to explore the biomechanical differences for measures of deceleration ability between a novel deceleration task, and the 505 change of direction test, using an inertial measurement unit-based technology. Primary findings suggested differences across several biomechanical characteristics quantified during the deceleration phase, with moderate to large between-test effect sizes. Specifically, subjects were found to exhibit significantly greater reductions in velocity and horizontal braking forces in the 505. Further, subjects showed significantly shorter stopping times and distances in the acceleration-deceleration assessment, however, these displayed insufficient levels of reliability across both assessments, which should be interpreted as a limitation. Therefore, it may be speculated that based on our data, the 505 test, which possesses a predetermined stopping/turning point, presents a greater or different biomechanical challenge to individuals, which must be met with the appropriate neuromuscular and skill-related qualities to efficiently reduce whole-body momentum. These findings may be relevant to practitioners interested in choosing the right assessment to quantify athletes’ maximal horizontal deceleration performance, which can have implications for both health and performance.

Braking and Propulsion Phase Characteristics of Traditional and Accentuated Eccentric Loaded Back Squats.

The purpose of this study was to examine the differences in braking and propulsion force-time characteristics and barbell velocity between traditional (TRAD) and accentuated eccentric loaded (AEL) back squats using various load combinations. Sixteen resistance-trained men participated in four separate testing sessions which included a one repetition maximum (1RM) back squat during the first session and three squat testing sessions. During the squat testing sessions, participants either performed sets of three repetitions of TRAD back squats each with 50, 60, 70, and 80% 1RM or performed the same loads with the addition of weight releasers that increased the total eccentric weight of the first repetition of each set to either 100 (AEL-MAX) or 110% 1RM (AEL-SUPRA). Braking and propulsion mean force, duration, and impulse as well as mean and peak barbell velocity were compared between each condition and load. Significantly greater braking impulses were produced during the AEL-MAX and AEL-SUPRA conditions compared to TRAD (p < 0.03) with small-moderate effect sizes favoring AEL-SUPRA. No other significant differences existed among conditions for other braking, propulsion, or barbell velocity variables. AEL-MAX and AEL-SUPRA back squats may provide a greater braking stimulus compared to TRAD squats; however, the propulsion phase of the movement does not appear to be impacted. From a loading standpoint, larger and smaller load spreads may favor rapid and maximal force production characteristics, respectively. Further research on this topic is needed as a large portion of the braking stimulus experienced during AEL back squats may be influenced by relative strength.

Research on Brake Energy Recovery Strategy Based on Working Condition Identification

As a transitional vehicle between fuel and electric vehicles, hybrid vehicles achieve energy savings and emission reductions without range anxiety. Regenerative braking has a direct impact on the fuel consumption of the whole vehicle; however, the current regenerative braking strategy for commercial vehicles is not yet perfect and has a poor adaptability in terms of working conditions and whole-vehicle load changes. Therefore, this paper proposes a regenerative braking strategy based on the identification of working conditions, by considering the influence of the vehicle load state and driving conditions on braking. Firstly, historical driving data of commercial vehicles were obtained from GPS data, driving conditions were classified using principal component analysis (PCA) and K-means, and a working condition recogniser was constructed using a back propagation neural network (BPNN) optimised with the Coati optimisation algorithm (COA). The recognition accuracy of the COA-BPNN was 7.6% better than that of the BPNN. Secondly, front and rear axle braking force distribution strategies are proposed, according to the braking intensity magnitude and load state under empty-, half-, and full-load conditions. Finally, a genetic algorithm (GA) was used to find the optimal control parameters for each category of working conditions, and the COA-BPNN condition recogniser identified the current category of working conditions needed to retrieve the corresponding optimal control parameters in the offline parameter library. The simulation results under C-WTVC and synthetic conditions show that the energy recovery rate of the proposed strategy in this paper reached up to 69.65%, which is at most 206.3% higher than that of the fixed-ratio strategy and at most 37.4% higher than that of the fuzzy control strategy.

Disturbance Observer-Based Tracking Control of High-Speed Trains Under Adhesion Dynamics

As the anti-skid control and speed tracking control of high-speed trains (HSTs) are interrelated and mutually constrained, it is very challenging to achieve simultaneous tracking of speed and slip ratio. In this paper, it is proposed for the first time that when the traction braking force has been limited to a reasonable range by the adhesion anti-skid condition, the high-precision tracking of the position and velocity curves of HSTs can be achieved, and the tracking error of the slip ratio is acceptable. Firstly, a novel modelling of the adhesion dynamics of HSTs under realistic gusts of wind disturbance is developed, and a model based on strict feedback is obtained by linearising the feedback for high-order non-linear systems. Then, this paper first presents the design scheme of fast terminal sliding mode controller based on disturbance observer for HSTs, which can ensure the anti-disturbance performance and accurate tracking of HSTs. Finally, an example is used to verify the validity of the results. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The actual traction/braking force of HSTs is provided by adhesion, and the existing literature on slip ratio tracking essentially sacrifices the tracking performance of the traction/braking system to meet the anti-skid requirements, while considering velocity and position tracking alone may leave the train in an undesired condition such as “idling” or “skidding”. This paper seeks to achieve high accuracy tracking of velocity and position profiles of HSTs under restricting the slip ratio to a reasonable range, which is expected to be an effective method for train tracking controller design. To avoid discomfort to passengers, nonlinearities dynamics are considered and an anti-disturbance controller is designed to compensate the impact of natural wind disturbances. To enhance the practicality, feedback linearization is introduced to reduce the complexity of the controller implementation. The designed fast terminal sliding mode controller also avoids jitter and singularity problems and obtains finite time stability. The stability analysis and numerical simulation have confirmed the effectiveness of the proposed scheme, which still needs to be verified by experiments in the future.

Does Walking with a Load Affect Asymmetry in Bilateral Lower Extremity Mechanics?

PURPOSE This study sought to analyze the velocity and asymmetry between bilateral lower extremity mechanics according to the load during walking.METHODS A total of 14 adults with right leg dominance participated in this study (Male=7, Female=7). We respectively applied 30% of body weight load carriage on the subjects. Gait characteristics were analyzed with 3-dimensional cinematography and ground reaction force (GRF) system consisted of a center of gravity (COG) velocity, center of pressure (COP) area, leg stiffness, and GRF components.RESULTS Change in velocity of the maximum-minimum COG showed statistically significant in the main effect of load. The 1st anterior-posterior GRF (braking force) and vertical GRF were statistically significant in the main effects of load and bilateral lower limbs. The 2nd anterior-posterior GRF (propulsive force) was statistically significant in the main effect of load. COP area and leg stiffness exhibited statistically significant differences in the main effects of load and bilateral lower limbs. Interaction was observed in the vertical GRF, COP area. Furthermore , one-way variance analysis revealed load main effect had a greater influence on the increase in the magnitude of the vertical GRF and COP area than the asymmetry of bilateral lower limbs.CONCLUSIONS This study revealed the differences in asymmetry between the dominant and non-dominant lower limbs according to the load during walking. These findings may explain the differences shock attenuation and stress mechanisms between the bilateral lower limbs.

Lower Extremity Kinematic and Kinetic Characteristics as Effects on Running Economy of Recreational Runners.

This study aimed to determine associations between running economy (RE) and running sagittal plane kinematic and kinetic parameters. A total of 30 male recreational runners (age: 21.21 ± 1.22 yr, V̇O 2max : 54.61 ± 5.42 mL·kg -1 ·min -1 ) participated in two separate test sessions. In the first session, the participant's body composition and RE at 10 and 12 km·h -1 were measured. In the second session, measurements were taken for the sagittal plane of hip, knee, and ankle angles and range of motion (ROM), as well as ground reaction force. Moderate correlations were found between lower energy costs at 12 km·h -1 and smaller hip flexion at toe-off ( r = 0.373) as well as smaller peak hip flexion during stance ( r = 0.397). During the swing phase, lower energy costs at 10 km·h -1 were moderately correlated with smaller peak knee flexion and smaller knee flexion and extension ROM ( r = 0.366-0.443). Lower energy costs at 12 km·h -1 were moderately correlated with smaller peak hip and knee flexion as well as knee extension ROM ( r = 0.369-0.427). In terms of kinetics, there was a moderate correlation between higher energy costs at 10 km·h -1 and larger peak active force, as well as larger peak braking and propulsion force ( r = -0.470-0.488). Lower energy costs at 12 km·h -1 were moderately to largely correlated with smaller peak impact and braking force ( r = 0.486 and -0.500, respectively). Regarding the statistical parametric mapping analysis, most outcomes showed associations with RE at 10 km·h -1 , including knee flexion (42.5%-65.5% of the gait cycle), ankle plantarflexion (32.5%-36% of the gait cycle), active force (30.5%-35% of the stance phase), and propulsion force (68%-72.5% of the stance phase). Lower energy costs at 12 km·h -1 were correlated with smaller hip flexion (5.5%-12% and 66.5%-74%) and smaller knee flexion (57%-57.5%) during the running gait cycle. This study indicates that biomechanical factors are associated with RE in recreational runners. To design effective training methods to improve RE, coaches and runners should focus on the sagittal plane kinematics of the hip, knee, and ankle, as well as lower vertical and horizontal kinetic parameters.

Effect of line parameters on wheel wear of heavy–haul freight vehicle

Purpose The serious wear problem of heavy-haul freight vehicle wheels affects the safety and economy of vehicle operation. This paper aims to study wheel wear evolution law and the influence of line parameters on wheel wear of heavy-haul freight, and provide the basis for operation and line maintenance. Design/methodology/approach The wheel wear test data of heavy-haul freight vehicles were analyzed. Then a heavy-haul freight vehicle dynamic model was established. The line parameters influencing wheel wear in heavy-haul freight vehicles were also analyzed by the Jendel wear model, and the effects of rail cant, rail gauge, rail profile and line ramp on wheel wear were analyzed. Findings A rail cant of 1:40 results in less wheel wear; an increase in the rail gauge can reduce wheel wear; and when matched with the CHN60 rail, the wear depth is relatively small. A decrease of 9.21% in wheel wear depth when matched with the CHN60 rail profile. The ramp of the heavy-haul line is necessary to consider for calculating wheel wear. When the ramp is considered, the wear depth increases by 8.47%. The larger the ramp, the greater the braking force and therefore, the greater of the wheel wear. Originality/value This paper first summarizes the wear characteristics of wheels in heavy-haul freight vehicles and then systematically analyzes the effect of line parameters on wheel wear. In particular, this study researched the effects of rail cant, rail gauge, rail profile and line ramp on wheel wear. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0038/