Braking Conditions Research Articles

Effect of disc materials on brake emission during moderate-temperature braking

Disc material effects on particle emission were investigated under moderate braking conditions using grey iron discs with different microstructures and a ceramic disc. The results demonstrate that brake emissions are strongly affected by disc hardness and the iron transferred to the pad surface. The transferred iron increased brake emissions due to the reduced cohesive strength of the plateaus on the pad surface. The grey iron microstructure also affected the ultrafine particle concentration owing to the graphite flakes. Conversely, the ceramic disc exhibited significantly lower brake emissions due to high wear resistance and no iron transfer to the pad surface.

Longitudinal–vertical comprehensive control for four-wheel drive pure electric vehicle considering energy recovery and ride comfort

The energy recovery efficiency and ride comfort of electric vehicles are important performance indicators. Currently, few joint studies have been conducted on the energy recovery and ride comfort of electric vehicles. For enhanced energy recovery and ride comfort, a comprehensive control method that contains neuro-fuzzy control and model predictive control is proposed herein. First, a longitudinal–vertical interaction model under braking conditions is established that includes longitudinal–vertical variables interaction. Second, model predictive control is adopted to adjust the active suspension for improving ride comfort with the braking intensity as the disturbance. Subsequently, to improve the energy recovery efficiency of the vehicle, a neuro-fuzzy optimization framework is proposed for optimizing the neuro-fuzzy membership function to realize neuro-fuzzy control, the framework considers the constraints of the vehicle vertical motion on the braking torque. Furthermore, the neuro-fuzzy control is adopted to control the vehicle powertrain. Finally, a dual-loop multi-stage control is selected for comparison. The simulation results under combined braking conditions indicate that the proposed comprehensive control method simultaneously improves the energy recovery efficiency and ride comfort of the vehicle.

Study on vibration and sound signals for fault diagnosis of hoist disc brake system

ABSTRACT The brake system of a mine hoist is the key component and the last barrier to ensure the safe operation in a mine. Based on the vibration and the sound signals of a test brake system, this paper studied the characteristics of the signals and the relationship between both the signals and tries to propose a new fault diagnosis method for the brake system. First, the vibration and sound signals of the test set-up under different braking conditions at different brake disc rotation speeds were collected. Then, the vibration and sound signals were filtered and reduced by the wavelet packet, and the reconstructed signal eigenvalues were extracted. The results showed that the characteristics of vibration and sound signals in fault state and normal state can be drawn. It shows the combined fault diagnosis method based on vibration and sound signals can see a wide application to the fault diagnosis for mine hoist brake system.

Establishing the requirements for the minimum values of stopping sight distance on the road surface from the condition of vehicle braking safely

The article is devoted to determine the stopping sight distance from the condition of the possibility stopping a car that moving at design speed. Determination is based on experimental studies of the dependences the coefficient of friction on the vehicle’s speed, when braking happens on the road surfaces that have the minimum permissible coefficient of friction value, established by the current regulatory literature. Braking of vehicles was studied on two surfaces with a minimum value of the coefficient of friction, but they were differing in surface roughness. Based on theoretically calculated braking distances, requirements for stopping sight distance with different design speeds have been developed. The obtained values of stopping sight distances are compared with the values contained in the normative documents of Russia and foreign countries.

Power distribution method for a parallel hydraulic-pneumatic hybrid system using a piecewise function

The Benedict-Webb-Rubin model or the ideal gas equation of state alone cannot accurately describe the load model of a parallel hydraulic-pneumatic hybrid system. This paper proposes a load model of the energy recovery system based on a piecewise function considering the load components switching problem under high energy regenerative braking and cruise charging conditions. This model can express the influence of the pre-charge pressure of the hydraulic accumulator and the air compressor speed on the system load power. This is accomplished by detecting the hydraulic accumulator state of charge, the transient temperature of nitrogen, and the transient temperature of the air in the reservoir. The load power of the energy recovery system can be estimated under various working conditions and used to guide the adjustment of the hydraulic pump/motor displacement to adjust the power distribution of the energy recovery system. This can solve the problem of ineffective power distribution and overspeed conditions, as well as fluctuation of the air compressor operation caused by changes in mechanical input power. The method proposed in this paper provides a new technical approach for the configuration of parallel hydraulic-pneumatic hybrid power systems.

Effects of braking conditions on nanoparticle emissions from passenger car friction brakes

Automobile friction brakes generate, in addition to coarse particles generated by mechanical processes, highly variable amount of nanoparticles from high temperature processes. The effects of braking conditions – speed, deceleration rate, brake rotor temperatures – on nanoparticle production were investigated here, aiming to provide practical guidance for reducing emissions through driving style and traffic management. Typical brake pads and a rotor from a common passenger car were subjected, on a brake dynamometer, to three runs of the WLTP brake cycle developed for brake wear particle measurements. Additionally, four sets of common brake pads were subjected to those parts of standardized brake performance tests believed to be reasonably realistic for common driving. Particle size distributions (5.6–560 nm electric mobility diameter, without removal of volatiles) show a dominant peak at 10 nm commensurate to the severity of braking and a non-linear increase of the total particle number at higher braking powers and higher total energy dissipated. The average emissions for three runs of the WLTP brake cycle were 3.3 × 1010 particles/km, while the harshest deceleration, 175–100 km/h at 5.28 m·s−2, has produced 8.4 to 38 × 1013 particles, corresponding to 2.5–11.5 thousands of km of WLTP-like driving. While previous studies have correlated higher PN production with higher average brake rotor temperature, a more complex relationship between nanoparticle emissions and a combination of initial rotor temperature, total energy dissipated and braking power has been observed here. From a driver behavior and regulatory perspective, it appears limiting harsh braking and braking from high speeds, possibly through improved driving practices, road design and traffic management, may potentially reduce brake wear nanoparticles. From the measurement perspective, it appears that “off-cycle” braking, even if relatively infrequent, may be associated with exponentially higher emissions and non-negligible share of the total emissions, and therefore should not be neglected.

Regenerative braking control under sliding braking condition of electric vehicles with switched reluctance motor drive system

To enhance braking energy recovery and improve braking comfort under sliding braking condition for electric vehicles (EVs) with switched reluctance motor (SRM), a novel regenerative braking control scheme based on braking force optimization controller and angle optimization controller is presented in this paper. Firstly, the current regulation method is developed, and the braking torque control strategy with four-phase currents and voltages of SRM drive system is proposed. Braking system (BS) of EVs including mechanical braking system and regenerative braking system is established. Then, the multi-objective optimization strategy (MOOS) for vital control parameters of regenerative braking system is proposed to improve regeneration braking comprehensive performance under sliding braking condition of EVs, where braking energy recovery efficiency, braking impact, and current fluctuation are considered as indexes to reflect working distance, braking smoothness, and battery lifetime of EVs, respectively. Furthermore, braking force optimization controller and angle optimization controller are developed by means of the multi-objective optimization results. Finally, compared to the efficiency optimization, the braking comfort optimization, and the current smoothness optimization strategy, the regenerative braking control scheme with MOOS can effectively increase working distance, improve braking smoothness, and extend battery lifetime of EVs under sliding braking condition. Furthermore, the real-time performance and effectiveness of the braking torque control strategy proposed are verified by simulation and PIL test.

Benefits estimation of regenerative braking versus service braking

A central question not yet examined in the literature is whether regenerative braking provides a kinematic deceleration safety advantage in time and distance over traditional service braking. This research explores three conditions of braking (traditional service braking, low level of regenerative braking, and high level of regenerative braking) to determine any safety advantages regenerative braking offers. Thirty participants took part in a simulator study with a between-subjects study design, allocating 10 participants per condition. The study drive took place in a simulator and involved three braking events. The results showed a significant difference between the means of the three conditions for average deceleration of the vehicle in the time interval between the driver releasing the accelerator and pressing the brake for all three events showing RB did provide the drivers with a braking advantage. When events 1 and 2 were combined, there was also significance with maximum brake force. Practitioner summary: This research looked to determine whether regenerative braking provides a deceleration safety advantage over traditional service braking. The results showed RB did provide the drivers with a braking advantage. The results also showed driver foot behaviour differed with the RB High condition.

Thermal-mechanical Coupling Analysis of Rear Wheel Brake of Sightseeing Vehicle Based on Workbench

Taking the rear wheel brake of a certain brand of sightseeing vehicle as an example, floating caliper disc brakes and leading trailing shoe brake were simulated and compared for determining rear wheel brake types. The simplified model is established by UG software, imported into Workbench for thermal-mechanical coupling analysis under 10 braking conditions. The results show that the two brakes can meet the requirements of the vehicle, the former has better performance, and the latter has lower cost.

Analysis of the Tire-Pavement Contact Stress Characteristics during Vehicle Maneuvering

The vehicle maneuvering condition plays an important role in the analysis of the contact stress characteristics of the tire-pavement interaction. A reliable three-dimensional (3D) tire-pavement interaction model was developed to simulate the interface contact stress at static and various rolling conditions (free rolling, acceleration and braking). First, the 205-55-R16 radial tire was modeled accurately comprised of its special pattern and materials in the finite element software ABAQUS. Next, we analyzed and compared these contact stress characteristics, including the distribution of contact stress, the peak contact stress and the variation of stress with time at free rolling, acceleration and braking conditions. Results showed that under the same vehicle load and inflation pressure, the tire-pavement contact stresses at free rolling condition are always much larger than those at static loading condition. At acceleration condition, the peak contact stress occurs at the inner edge of the tire outermost ribs. At deceleration condition, the stress concentration on the tire tread is weakened with the extension of time. The peak contact stress increases with time at acceleration and braking conditions. But the peak contact stress at braking is much larger than that at acceleration condition under the same load and inflation pressure.

Energy-Efficient Braking Torque Distribution Strategy of Rear-Axle Drive Commercial EV Based on Fuzzy Neural Network

<div class="section abstract"><div class="htmlview paragraph">Regenerative braking is identified as an essential step toward extending cruising mileage for electric vehicle (EV). Braking energy recovery strategies usually focus on passenger EV and commercial EV is ignored. In this paper, an energy-efficient braking torque distribution strategy is proposed for a rear-axle drive commercial EV to improve braking energy recovery and safety. Firstly, the braking force distribution curve is determined referring to the EU braking law for commercial vehicle and the ideal braking distribution curve. Secondly, a novel braking torque distribution strategy is established adopting fuzzy control algorithm, where the ratio between hydraulic braking torque and regenerative braking torque is updated instantaneously according to vehicle velocity, braking strength and state of charge of battery. Then, the corresponding controller is synthesized on ideal braking condition and several classic cycles. To further enhance the performance of the controller, a neural network based framework is established to optimize the membership function in fuzzy controller. Simulations on ideal braking condition demonstrate the controller can always meet emergency braking needs. For the standard cycles, including NEDC and WLTC, the energy-efficient strategy based on fuzzy control can recover up to 18.88% and 16.56% of energy under NEDC and WLTC cycles, and on this basis, the optimized strategy based on adaptive neuro-fuzzy control can improve energy recovery by 2.84% and 3.6% under these two cycles. The developed braking torque distribution strategy can potentially be embedded in real-time supervisory systems to realize the energy saving and increase the cruising mileage for commercial EV.</div></div>

Modelling on Novel Cable Traction Power Supply System and Power Distribution Analysis

Novel cable traction power supply system (NCTPSS) is a kind of long distance co-phase traction power supply system (TPSS), it can effectively solve problems caused by train's passing through electrical phase separation and improve utilization rate of regenerative energy in system, which is an ideal traction power supply mode. However, its structure is relatively complex due to cable power supply pattern, and internal power flow distribution mechanism still needs further study. In order to establish train-network coupling power flow calculation model, in this paper, two-port network model of each system component is established at first, then equivalent solid circuit model of the system is built by external cascade strategy and tearing nodal method. Then, power flow, the change of traction transformer power output and network voltage are analyzed under the condition that trains work in traction and regenerative braking condition, based on actual train operation schedule. The research shows that the proposed model can accurately calculate and detailed reflect electrical characteristics of NCTPSS, traction transformer capacity is effectively decreased compared with that needed in existing TPSS; Regenerative power can feed back to entire cable traction network and be reused by traction trains with high utilization rate inside NCTPSS.

Modelling the longitudinal braking dynamics for heavy-duty vehicles

This paper establishes a reliable heavy-duty braking system model that can be used for response time prediction and for vehicle braking calculations regarding the legislative requirements. For the response time prediction, a pneumatic system model of a heavy-duty vehicle is constructed by Matlab Simulink in consideration of service brake layout. To ensure the accuracy of system parameters related with pneumatic system response time experiments are conducted on two different 4 × 4 heavy-duty vehicles. The numerically calculated response time results are validated with experimental data. To improve the response time of the vehicle, design modifications are conducted on the pneumatic brake system properties. To check the compliance of the pneumatic brake system design with legislative requirements of UN Regulation 13, heavy-duty vehicle brake system (HVBS) model is developed by using Matlab Simulink. HVBS model is composed of longitudinal vehicle and wheel dynamics, Magic Formula tyre model, wheel slip and the experimentally verified heavy-duty pneumatic system model. The braking performance analyses are conducted by using HVBS model to compare the design alternatives in accordance with the legal requirements in terms of service braking and secondary braking conditions.

Experimental evaluation of braking pad materials used for high-speed elevator

In this paper, an elevator safety gear braking testing rig was developed based on the disc-pad braking model in principles of energy equivalent and speed equivalent to evaluate the braking behavior of short carbon fiber (SCF) reinforced carbon/carbon (C/C) composite and Cu-based powder metallurgy (P/M) material. Note that the braking pressure and the initial braking speed were controlled between 10 MPa to 56 MPa and 3 m/s to 25 m/s respectively in the experiment, which covers the real braking conditions in high-speed elevator. Then friction behaviors of both braking materials were investigated. Especially, the dependence of the coefficient of friction (COF) on the braking pressure and initial braking speed were minutely studied. Interestingly, it was found the COFs increased with the initial braking speed, but decreased with the improved braking pressure. Besides, wear behaviors under different braking conditions for both materials were explored. Results showed the C/C composite pads were crushed at high initial braking speed (V ≧ 14 m/s) in this experiment, but the Cu-based P/M material could suffer higher initial braking speed, which suggested the Cu-based P/M material had more potential to be used as the braking material applied in high-speed elevator or even ultra-high speed elevator compared to C/C composite adopted in this paper.

Anti–Drag Braking Control Technology for Electric Drive Dump Truc

The power transmission system of electric wheel vehicle with "Power generator - diode rectifier - inverter - traction motor" can achieve part of the braking energy recycling and reduce fuel consumption through the reverse flow of energy in the downhill braking conditions. For AC - DC - AC transmission system of electric wheel vehicles. In order to achieve the engine anti-drag starting smoothly through the introduction of the theory of Engine Anti - drag Braking and the observation of the rotor frequency by external speed sensor, in addition to that zero-crossing detection phase method to achieve the stator rotating magnetic field and rotor speed synchronization purposes. Through use the rectifier inverter module to achieve energy bi-directional transmission and to achieve engine anti-drag when the vehicle goes downhill slowly. In the article, design of engine brake anti-drag control system and the establishment of anti-drag brake power calculation mathematical model, also build the anti-drag test platform of the engine to verify the control system. The experimental results show that the proposed control scheme for the start of the inverter is simple and reliable, which provides the theoretical basis and experimental data for the actual vehicle design.

Підвищення якості автотехнічної експертизи дорожньо-транспортних пригод в умовах композиційної невизначеності

Decision-making in solving the problems of auto technical examination of road accidents (road accidents) is carried out in conditions of incomplete information, ie in conditions of uncertainty, which may be stochastic or fuzzy in nature, and therefore is compositional. When forming expert opinions of auto technical examination of road accident the general uncertainty is formed due to uncertainty of the chosen structure of model of road accident, experimental data, error of measuring devices, adequacy of model of road accident, uncertainty of indications of witnesses and other proofs, competence and honesty of the expert. The calculation of vehicle parameters in motor vehicle expertise in the vast majority of cases is performed without estimating the error of the results, which does not meet the requirements of the Law of Ukraine "On Metrology and Metrological Activity" and determines the relevance of improving methods of solving road accident technical examination. The paper reveals the prospects of improving the existing methods of assessing the effectiveness of braking of wheeled vehicles, as the main way to prevent accidents in road transport, which is regulated by the current Traffic Rules. The basic theoretical dependences which form a basis of the improved technique of estimation of parameters of movement of cars at braking are presented. Analysis of the results of the calculations shows that by taking into account the design of the braking system, type and condition of tires used in assessing braking efficiency, the improved technique avoids the same solutions within one category of vehicles, and taking into account stochastic and fuzzy uncertainty narrows the range of possible solutions by 49.4 %. The probability of occurrence of type I errors is reduced by 1.75-18.5%, and type II errors - by 43.1-67.8%.

Comparative analysis of internal flow characteristics of LBE-cooled fast reactor main coolant pump with different structures under reverse rotation accident conditions

Lead alloy is used as coolant in Lead-based cooled Fast Reactor (LFR). The natural characteristics of lead alloy are combined with the simple structural design of LFR. This constitutes the inherent safety characteristics of LFR. The main work of this paper is to take the main coolant pump (MCP) in the lead-cooled fast reactor (LFR) as the research object, and to study the flow pattern distribution of the internal flow field under the reverse rotation pump condition, the reverse rotation positive-flow braking condition and the reverse rotation negative-flow braking condition. In this paper, the double-outlet volute type and the space guide vane are selected as the potential designs of the CLEAR-I MCP. In this paper, the CFD method is used to study the potential reverse accident of the MCP. It is found that the highest flow velocity in the impeller appears at the impeller outlet, and the Q-H curves of the two design programs basically coincide. The space guide vane type MCP has better hydraulic performance under the reverse rotation positive-flow condition, the Q-H curves of the two designs gradually separate with increasing flow rate, and the maximum flow velocity inside the space guide vane type MCP is obviously lower than that of the double-outlet volute type. For the reverse rotation test of MCP, only the condition of the forward rotating pump of the main coolant pump is tested and verified. For the simulation of the MCP in LBE medium, it proved that the turbulence model and basic settings selected in the simulation are reliable.

Thermal analysis of a novel retarder by using the nanofluid cooling system: Numerical and experimental approaches

AbstractTo solve the problem of braking torque decline or even brake failure of vehicle retarders caused by high temperature due to long‐time or high‐power braking, the nanofluid with high thermal conductivity is introduced into the previously proposed novel retarder. To evaluate the nanofluid cooling capabilities, a model depicting the vertical fluid flow in the retarder is formulated. Adopting similarity transformations and a shooting method coupled with Runge–Kutta iterative technology, the model boundary value problem is tackled numerically. The cooling capabilities of three typical ethylene glycol (EG)‐based nanofluids: Cu–EG, Al2O3–EG, and TiO2–EG are investigated and compared. Finally, an experimental test is carried out to examine the temperature rise and the variation of braking torque for the retarder. It is demonstrated that Al2O3–EG nanofluid has the highest Nusselt number (rate of heat transfer), and more importantly, the braking torque of the proposed retarder decreases by only 8.2% under high‐power braking condition.

An improved degraded adhesion model for wheel–rail under braking conditions

Purpose The purpose of this paper is to develop an improved adhesion model to better reproduce the low adhesion condition of the anti-skid control for rail vehicles under braking condition. Design/methodology/approach In view of the low adhesion characteristics for rail vehicles under braking conditions, the Polach adhesion model was improved based on the sliding power and sliding energy. The wheel–rail low adhesion model suitable for braking condition was given. The analysis of braking anti-skid control under emergency braking condition was carried out through the co-simulation, and compared with the test data; the effectiveness and practicability of the improved low adhesion model were verified. Findings The results showed that the improved adhesion model is simple and efficient and the parameters involved are less, and it can be directly applied to the real-time simulation of anti-skid control in the process of train braking. Originality/value This paper can provide a theoretical reference for the reasons of change and improvement of adhesion between wheel and rail caused by the adjustment of braking force under anti-skid control, which can fulfill a need to the study of sliding energy on the contact surface, the removal effect of pollutants on the wheel–rail surface and the improvement and recovery of adhesion caused. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0244/

The wet braking and recovery behaviors of the P/M pad mated with C/C–SiC disc for high-speed trains

C/C–SiC ceramic is a promising braking material in high-speed trains. The research on wet braking is necessary for its application. In this paper, braking tests of C/C–SiC disc mated with powder metallic (P/M) pads were conducted under dry, wet and recovery braking conditions at initial braking speed (IBS) of 14, 22, 33, 44, 55 m/s. Coefficient of friction (COF) and surface morphologies under different conditions were discussed: The instantaneous COF under wet condition was lower but the instantaneous COF curves became smoother than those under dry condition. The difference between two conditions went smaller as IBS increased. Under recovery condition, it cost 33 stops at 14 m/s to recover to 93.1% of the origin COF. Meanwhile, 8 stops were needed at 55 m/s, and the recovery rate was 98.9%. When the IBS increased, the number of the stop needed was fewer and the recovery rate was higher. The surface morphologies further showed the braking under wet condition resulted in a smoother surface with less ploughing grooves and the disappearance of the friction film. Under the recovery condition, the surface became rough again with grooves and the friction film formed again. The results indicate that the wear debris were washed away by the sprayed water and the formation of friction film was inhibited. In addition, water film subsequently lubricated the friction surface, which reduced COF at low IBS. As IBS increased, high temperature accelerated the dewatering and evaporation of water and thus lead to the decrement of the COF difference between wet and dry friction which, in turn accelerated the recovery process.