Braking Speed Research Articles

Energy-efficient speed profile: an optimal approach with fixed running time

Tracking the optimal speed profile in electric train operation has been proposed as an efficient and feasible solution for not only reducing energy consumption, but also no at costs to upgrading the existing railway systems. This paper focuses on finding the optimal speed profile based on Pontryagin’s maximum principle (PMP) while ensuring the fixed running time, and comparing energy saving levels in the cases of applying or not applying PMP. The way to determine the fixed running time also differs from works published is to calculate the total trip time equal to scheduled timetable exactly. Calculating accelerating time t a , coasting time t c , braking time t b via values of maximum speed v h , braking speed v b of optimal speed profile. The other hands, v h and v b are determined by solving nonlinear equations with constraint condition: the running time equal to the demand time. Simulation results with data collected from electrified trains of Cat Linh-Ha Dong metro line, Vietnam show that energy reduction for the entire route when PMP utilization is up to 8.7% and running time complied with scheduled timetables.

Tribological Properties of Laminate Composite Brake Material for High-Speed Trains

In this article, a laminate composite brake material was prepared by powder metallurgy techniques and proposed for use in the high-speed train braking system. The pad was a double-layer structure composed of prefabricated tribofilm (PTF, oxide-based materials) and metal-based materials. The friction and wear behaviors of the novel friction material with different thicknesses of PTF layer against steel rotor disc were investigated using a TM-I type braking dynamometer under initial braking speeds (IBS) of 50–350 km/h. It was found that the PTF pad exhibited stable friction behavior and wear rate in a large range of IBS (50–250 km/h), meeting the requirements of high-speed trains. During braking, the friction film formed on the worn surface was closely related to the friction and wear behavior. The PTF promoted the formation of a protective friction film, which provided a larger and flatter surface than that of metal-based materials. A relatively stable friction behavior and wear rate were maintained when the worn surface was covered with friction film.

Substantiation of the limiting speed of shock braking of the feeder when moving the loose assembly to the assembly position

The speed of impact braking of the feeder is substantiated when moving an unsecured node with the occurrence of only elastic deformations on the interacting surfaces, at which the node will not be displaced relative to its original position.

Sex differences in cognitive-motor components of braking in older adults.

Fast and accurate braking is essential for safe driving and relies on efficient cognitive and motor processes. Despite the known sex differences in overall driving behavior, it is unclear whether sex differences exist in the objective assessment of driving-related tasks in older adults. Furthermore, it is unknown whether cognitive-motor processes are differentially affected in men and women with advancing age. We aimed to determine sex differences in the cognitive-motor components of the braking performance in older adults. Fourteen men (63.06 ± 8.53 years) and 14 women (67.89 ± 11.81 years) performed a braking task in a simulated driving environment. Participants followed a lead car and applied a quick and controlled braking force in response to the rear lights of the lead car. We quantified braking accuracy and response time. Importantly, we also decomposed response time in its cognitive (pre-motor response time) and motor (motor response time) components. Lastly, we examined whether sex differences in the activation and coordination of the involved muscles could explain differences in performance. We found sex differences in the cognitive-motor components of braking performance with advancing age. Specifically, the cognitive processing speed is 27.41% slower in women, while the motor execution speed is 24.31% slower in men during the braking task. The opposite directions of impairment in the cognitive and motor speeds contributed to comparable overall braking speed across sexes. The sex differences in the activation of the involved muscles did not relate to response time differences between men and women. The exponential increase in the number of older drivers raises concerns about potential effects on traffic and driver safety. We demonstrate the presence of sex differences in the cognitive-motor components of braking performance with advancing age. Driving rehabilitation should consider differential strategies for ameliorating sex-specific deficits in cognitive and motor speeds to enhance braking performance in older adults.

Thermal Modelling of a Disc Brake System at Different Vehicle Weights and Constant Speeds

In this study, three-dimensional thermal modelling has been made for a disc brake mechanism of an automobile by using the COMSOL Multiphysics programme. Frictional heat has been calculated by means of multibody dynamic module, and heat distribution has been calculated by means of heat transfer module. In such model, an automobile with an initial speed of 25 m⁄s and 35 m⁄s has been decelerated by -10 m⁄s^2 braking speed, and the braking state has been realised at time interval of 2-4 s. Thermal analysis has been made for two different vehicle weights (1200 kg-1500 kg) under the same braking scenario. The results obtained from the thermal analysis have shown similarity to various studies carried out within the literature. An increase of 300 kg in vehicle weight has resulted in a temperature increase by 3.33% during motion at 25 m⁄s vehicle speed, and by 6.03% during motion at 35 m⁄s vehicle speed. According to temporal temperature change, maximum pad temperature has been obtained at the 4th second; and in the case that the vehicle with a weight of 1500 kg and moving at 35 m⁄s speed has braked, maximum pad temperature has been obtained as 450 K.

КОНЦЕПЦІЯ ОЦІНКИ ГАЛЬМІВНОЇ ЕФЕКТИВНОСТІ ВАНТАЖНИХ ПОЇЗДІВ ЗА РЕЗУЛЬТАТАМИ ЕКСПЕРИМЕНТАЛЬНИХ ДОСЛІДЖЕНЬ У РОЗРІЗІ ВИМОГ ГОСТ 34434-2018

The approach of experimental study of the freight trains braking efficiency using computer simulation based on the implementation of the simulation model in the form of a differential equation of the wagon motion during braking, is proposed. The methodology of experimental studies is based on universal formulas for power-law dependences of braking parameters. The braking efficiency is evaluated by the use of computer software packages written in VBA (Visual Basic for Application) in Excel. The software package al-lows you to increase the automation of testing, the accuracy of calculations, to reduce the time for testing, and also minimize the number of errors caused by the human factor. The presented methodology significantly extends the number of parameters of the braking process used to analyze the braking efficiency of a freight train based on the results of running braking tests: actual values of braking coefficients; braking distances of a freight train not only on the site, but also on normalized gradient descents for a given number of wagons in the train, taking into account the increase in the braking force along the wagons in the train formation; actual values of wheel and rail adhesion coefficients during braking; the deceleration of the freight wagon and the train during braking, as well as the braking time. Examples of computational and experimental studies of a freight train with tread brake are given. A comparative analysis of experimental and computational studies demonstrates sufficiently satisfactory matching of their results. Key words: freight train, braking distance, braking speed, braking coefficient, increase in braking force, mathematical model, trend line, braking wave.

A novel method for determining fixed running time in operating electric train tracking optimal speed profile

<span lang="EN-US">Tracking the optimal speed profile in electric train operation has been proposed as a potential solution for reducing energy consumption in electric train operation, at no cost to improve infrastructure of existing Metro lines as well. However, the optimal speed profile needs to meet fixed running time. Therefore, this paper focuses on a new method for determining the fixed running time complied with the scheduled timetable when trains track the optimal speed profile. The novel method to ensure the fixed running time is the numerical-analytical one. Calculating accelerating time ta, coasting time tc, braking time tb via values of holding speed vh, braking speed vb of optimal speed profile with the constraint condition: the running time equal to the demand time. The other hands, vh and vb are determined by solving nonlinear equations with constraint conditions. Additionally, changing running time suit for each operation stage of metro lines or lines starting to conduct schedules by the numerical-analytical method is quite easy. Simulation results obtained for two scenarios with data collected from electrified trains of Cat Linh-Ha Dong metro line, Vietnam show that running time complied with scheduled timetables, energy saving by tracking optimal speed profile for the entire route is up to 8.7%, if the running time is one second longer than original time, energy saving is about 11.96%.</span>

Oxidation behaviour of C/C–SiC brake discs tested on full-scale bench rig

C/C–SiC composites are considered to be strong candidates for the new generation of high-speed train brake discs. To achieve a better application, it is necessary to improve understanding of the oxidation behaviour of C/C–SiC brake discs after a full-scale bench test rig. In this study, full-scale braking bench tests for C/C–SiC self-mated brake pairs were conducted under a braking speed of 350–420 km/h and a braking pressure of 17–28 kN. Moreover, the oxidation behaviour and mechanisms of the C/C–SiC brake discs during the practical braking process were investigated. The results indicate that the oxidation behaviour is highly dependent on the friction surface region of the C/C–SiC brake disc owing to the distribution of microcracks, the formation of friction films, the difference in temperature, and the contact content with O 2 . Specifically, the oxidation depths of the friction layer on the inner circumferential surface, middle friction surface, and outer circumferential surface were 278.3, 252.1, and 359.9 μm, respectively. Furthermore, the oxidation reaction preferentially occurs in the active area of the C fibre and pyrolytic carbon (PyC) during the braking process.

Evaluation of two power assist systems for manual wheelchairs for usability, performance and mobility: a pilot study

Background Power-assist devices for manual wheelchairs offer benefits, including increased community participation. Several power-assist devices are commercially available, but research on benefits and limitations of devices is limited. Objective To compare the usability, performance, and mobility of two power-assist device systems for manual wheelchairs in indoor and outdoor environments. Methods This mixed methods pilot study included 11 volunteers with limited wheelchair experience. Participants tested two different power-assist device configurations: (1) the Batec® and (2) the SmartDrive® + Freewheel®. Indoor & outdoor obstacle courses contained relevant skills from the Wheelchair Skills Test, Power Mobility Community Driving Assessment, and Power Mobility Indoor Driving Assessment. The NASA Task Load Index and System Usability Scale assessed participants’ perceptions of cognitive demand and usability. A semi-structured interview was conducted to explore participants’ experiences. Results Substantial differences were found in the NASA Task Load Index, and System Usability Scale scores. Participant interviews and researcher observations revealed each device performed better on some obstacle course elements. Qualitative findings showed a general preference for using the Batec® for long trips outside and off-road terrains, primarily due to the Batec’s® perceived better speed control, maximum speed, and simpler braking system. Conversely, the SmartDrive® + Freewheel® was deemed most useful indoors and in tight spaces; due to a smaller wheelchair footprint, better turning radius, and increased device portability. Conclusion Further studies are required to understand the usability, performance, and mobility of power-assist devices. Moving forward, these findings will inform end users and occupational therapists when procuring manual wheelchair power-assist devices. Implications for rehabilitation Power-assist devices (PADs) for manual wheelchairs increase the potential for community participation. Qualitative findings showed a general preference for using the Batec® for long trips outside and for off-road terrains, primarily due to the Batec’s® perceived better speed control, maximum speed, and simpler braking system. The SmartDrive® + Freewheel® was deemed most useful indoors and in tight spaces; due to a smaller wheelchair footprint, better turning radius, and increased device portability. Increasing knowledge and research about PADs will support development of alternative options for manual or power wheelchairs users. PADs may allow manual wheelchair users (MWC) to delay moving to a power wheelchair (PWC), potentially reducing the perceived stigma associated with transitioning to a power wheelchair and impacting health outcomes.

Energy-efficient speed profile: An optimal approach with fixed running time

Tracking the optimal speed profile in electric train operation has been proposed as an efficient and feasible solution for not only reducing energy consumption, but also no at costs to upgrading the existing railway systems. This paper focuses on finding the optimal speed profile based on Pontryagin's maximum principle (PMP) while ensuring the fixed running time, and comparing energy saving levels in the cases of applying or not applying PMP. The way to determine the fixed running time also differs from works published is to calculate the total trip time equal to scheduled timetable exactly. Calculating accelerating time t a , coasting time t c , braking time t b via values of maximum speed v h , braking speed v b of optimal speed profile. The other hands, v h and v b are determined by solving nonlinear equations with constraint condition: the running time equal to the demand time. Simulation results with data collected from electrified trains of Cat Linh-Ha Dong metro line, Vietnam show that energy reduction for the entire route when PMP utilization is up to 8.7% and running time complied with scheduled timetables.

Determination of Braking Speed of Developed Hybrid Particle Reinforced Aluminium Alloy

Abstract- This paper is aimed at comparing the braking speed of the developed Composite Brake Disc (CBD) with that of a nodular cast iron Honda Accord (2000) Model Brake Disc (HABD). The test samples were produced from Aluminium alloy (Al6061), Coconut Shell Ash (CSA) and Silicon Carbide (SiC) by Stir casting and machined into standard specimens for microstructure analysis, density test, mechanical tests (hardness, tensile and impact), wear test and thermal test. The characterization of coconut shell ash particle was carried out using X-ray Flourescent equipment. Six samples were produced, four composite samples; C1 (70% Al, 5% SiC, 20% CSA), C2 (70% Al, 10% SiC, 15% CSA), C3 (70% Al, 15% SiC, 10% CSA) and C4 (70% Al, 20% SiC, 5% CSA), aluminium alloy sample (A1) and as-cast nodular cast iron sample (N1) obtained from HABD. Sample ‘C4’ had the best physical, mechanical, wear and thermal properties (Densty: 3.15 g/cm3, Hardness: 68 kg/mm2, Tensile Strength: 196.12 N/mm2, Impact Energy: 8.05 J, Wear rate: 0.0002328 g/m, Thermal Conductivity: 72.57 W/m-K) and was used to produce the CBD. From the values of coefficient of frictions obtained for CBD and HABD, the braking speeds were calculated and HABD was seen to have a lower braking speed (56.65 m/s) than the CBD (94.42 m/s) because of its higher coefficient of friction. The higher braking speed of the composite brake disc (CBD) as compared to the Honda Accord Brake Disc (HABD) could be as a result of inadequate reinforcements in the aluminium alloy matrix. Hence, the produced CBD cannot be used as an alternative for the nodular cast iron Honda accord brake disc (HABD) even as problems of heavy weight and breakage that may occur due to heavy impact associated with cast iron brake disc have been addressed using the developed composite.Keywords,- Aluminium Alloy, Braking Speed, Coconut Shell, Composite, Silicon Carbide

Bifurcation and Chaotic Behaviors of Vehicle Brake System Under Low Speed Braking Condition

Bifurcation and Chaotic Behaviors of Vehicle Brake System Under Low Speed Braking Condition

Evaluation of Wear of Disc Brake Friction Linings and the Variability of the Friction Coefficient on the Basis of Vibroacoustic Signals

The article presents the results of friction and vibroacoustic tests of a railway disc brake carried out on a brake stand. The vibration signal generated by the friction linings provides information on their wear and offers evaluation of the braking process, i.e., changes in the average friction coefficient. The algorithm presents simple regression linear and non-linear models for the thickness of the friction linings and the average coefficient of friction based on the effective value of vibration acceleration. The vibration acceleration signals were analyzed in the amplitude and frequency domains. In both cases, satisfactory values of the dynamics of changes above 6 dB were obtained. In the case of spectral analysis using a mid-band filter, more accurate models of the friction lining thickness and the average coefficient of friction were obtained. However, the spectral analysis does not allow the estimation of the lining thickness and the friction coefficient at low braking speeds, i.e., 50 and 80 km/h. The analysis of amplitudes leads to the determination of models in the entire braking speed range from 50 to 200 km/h, despite the lower accuracy compared to the model, based on the spectral analysis. The vibroacoustic literature presents methods of diagnosis of the wear of various machine elements such as bearings or friction linings, based on amplitude or frequency analysis of vibrations. These signal analysis methods have their limitations with regard to their scope of use and the accuracy of diagnosis. There are no cases of simultaneous use of different methods of analysis. This article presents the simultaneous application of the amplitude and frequency methods in the analysis of vibroacoustic signals generated by brake linings. Moreover, algorithms for assessing the wear of friction linings and the average coefficient of friction were presented. The algorithm enables determination of the time at which the friction linings should be replaced with new ones. The final algorithm analyzes the vibration acceleration signals using both amplitude analysis for low braking speeds, as well as spectral analysis for medium and high braking speeds.

Research on regenerative braking system for linear control chassis platform

The regenerative braking system of the electric vehicle with the linear control chassis plays an important role in improving the mileage of the vehicle, which mainly solves the problem of large electricity demand for the linear control chassis. After analyzing the structural characteristics of the linear control chassis, the constraints of regenerative braking and the existing regenerative braking control strategies, a new regenerative braking control strategy is proposed, and the control strategy is modified. The regenerative braking control strategy model is established by Simulink / Stateflow, and the braking effect and energy recovery efficiency are verified by changing the initial braking speed. The simulation results show that the strategy can well complete the braking task of the vehicle, and the braking energy recovery rate increases with the increase of the initial braking speed. Reasonable control strategy can effectively improve vehicle energy recovery efficiency.

Effect of h‐BN addition on friction and wear properties of C/C‐SiC composites fabricated by LSI

AbstractHexagonal boron nitride (h‐BN) has excellent oxidation resistance, self‐healing function, and self‐lubricating properties, which can significantly improve the oxidation resistance of C/C‐SiC composites in low or medium temperature condition and affect their tribological properties and mechanisms. In this work, C/C‐SiC and C/C‐BN‐SiC composites were prepared by the same molding, carbonization and liquid silicon infiltration (LSI) process and the influences of h‐BN addition on their microstructure, tribological properties, and mechanisms were investigated. h‐BN addition can promote the formation of friction film and reduce the oxidation wear of the composites. Compared with C/C‐SiC composites, due to more lubricant components and different matrix structure, the C/C‐BN‐SiC composite shows lower wear rate (reduced by 53%) and moderate rather than too high coefficient of friction (CoF) and its CoF is less influenced by braking velocity. Moreover, the friction process is more stable and does not appear clamping stagnation phenomenon in high braking speed condition.

Effects analysis of light-duty diesel truck hybrid conversion depending on driving style

• Effects of hybrid conversion of a light-duty diesel truck are investigated. • The hybrid conversion improves the fuel economy by 24.3% on average. • The fuel economy benefit from hybrid conversion is dependent on driving style. • Adaptive control can make the HEV hardly dependent on average engine speed. • Visual feedback to the unaware driver can further improve the fuel economy by 13.3%. This study performs an effects analysis of the hybrid conversion of a light-duty diesel truck depending on driving style. The experimental route is extracted from real delivery routes, and multiple drivers drive the route several times before and after the conversion. The results confirm that the fuel economy is improved by 24.3% on average after the conversion, and the fuel economy before and after the conversion is most strongly dependent on average engine speed and regenerative braking ratio, respectively. This different dependence on the driving style parameters is analyzed in relation to the control strategy and powertrain of the converted truck. An additional experiment reveals that the fuel economy of the converted truck can be further improved by 13.3% when visual feedback is provided to the unaware driver for correcting driving styles. These findings can be utilized to improve the performance of hybrid electric vehicles for various driving styles.

Study on the Ice-Coated Brake Disc for EMUs Based on Force Coupling

Based on the abnormal wear of the brake disc of Electrical Multiple Units (EMUs), considering the ice-coated friction pair, the finite element (FE) models of the brake disc, the friction blocks and ice impurity were established in ANSYS to explore the stress characteristics of the brake disc. For the ice-coated model, it is found that the maximum equivalent stress is 956.75MPa under the condition of pad stress of 25kN and initial braking speed of 250 km/h. The value of the maximum stress on brake disc surface decreased by 400MPa while removing the ice impurity. The maximum Z-displacement on the ice-coated disc is nearly 4.7mm, and with the contact point farther away, the smaller the deformation will be. The overall trend of the equivalent stress and Z-displacement of the brake disc increases with the braking pressure increasing. Droplet-like frictional blocks can improve the maximum stress and Z-displacement of the disc. Therefore, it is suggested that droplet -like frictional blocks are used for the braking equipment. For improving abnormal wear of the brake disc in extremely cold and snow environment, the analysis provides important reference and theoretical basis for engineering.

A comparison of PSO and Fmincon methods for finding optimum operating speed and time values in trams

All the studies in urban railways gained importance with the requirement of developing in this area. However, not only technological development but also energy-saving conditions have great importance. One of these efficiency conditions is to know the optimum operating conditions. There are two electronic drive-warning systems. These warning systems are Driver Advisory System (DAS) and Automatic Train Operation (ATO), which are algorithm-based. To enrich these algorithms with meta-heuristic methods provides that it can be adapted to the changing operating conditions. Thus, flexible management can be achieved.
 In this study, the Particle Swarm meta-heuristic and Fmincon which is a nonlinear programming solver in MATLAB methods are used to calculate optimum driving speed, acceleration, cruising, coasting, and full braking times under different operating conditions. Comparative optimization results of these selected methods are presented. Thus, attention is drawn to the efficiency in driving technique with different optimization methods. Specific speed-specific driving time matches obtained can be used to develop innovative driving warning systems.

Design of Personal Mobility Safety System Using AI

In this paper, we propose the implementation of a safety device that generates an alarm sound or braking operation to reduce the risk of accidents. It reduces the exposure of risks due to non-wearing by supplementing the function of the helmet for safety. For machine learning, the safety state is learned by using two types of sensing data, and when an abnormal helmet use or speed or drinking driving is detected, an alarm sound is generated and motion is broken to maintain the safe state. By measuring data using a gas sensor, alcohol is checked and this is used as abnormal data. Users form a habit of wearing safety equipment with continuous safety alarm sound and speed braking and proper driving habit by driving in a normal state without drinking alcohol. In addition, the proposed system enables real-time monitoring, thereby reducing risks by continuously maintaining safe driving and wearing protective equipment. The proposed system uses artificial intelligence to discriminate data related to helmet wearing, speed, and drinking in making an electric kickboard for safety, and triggers an alarm or operates the brake to prevent abnormal driving. If the design and function are supplemented, it will become a basic function that can be applied to various equipment of transportation.

Capacity increasing of arterial streets with controlled motion

The problem of capacity increasing of arterial streets with controlled motion is investigated in this paper. For investigation, sections between intersections on the road network of Lviv city were chosen at their different length and roadway width with most saturated traffic. Methods of capacity increasing of arterial streets with controlled motion and factors that have impact on the capacity reduction are analyzed. Capacity of intersections at different volume-capacity ratios is determined. The distribution of average speed for sections between intersections of different length is built. It is established that on sections of medium length between signalized intersections and the high volume-capacity ratio, the speed of traffic flow does not reach maximum values. It is possible to increase the speed and the capacity of sections between intersections by increasing their length, sufficient for flow acceleration to the maximal constant speed and further braking before the intersection. To determinate the recommended speed of movement on arterial directions, road conditions are taken into account, which are formed with simultaneous impact of several factors: volume-capacity ratio of intersection in braking zone, volume-capacity ratio of intersection in acceleration zone, the number of lanes, the length of the section between intersections and the average speed of the traffic flow. It is determined that the average speed of traffic flow on short sections between intersections (the length less than 300 m) is 27 – 33 km/h, on sections of medium length – 35 – 38 km/h/ Such speed will allow to traffic flow reaching the line of constant movement in given road conditions. Conducted research allows taking into account road traffic conditions while justifying the calculating speed of traffic flow, in result of which capacity of arterial streets of controlled motion increases.