Braking State Research Articles

Do the sparser access points have less impact on arterial traffic? A microscopic simulation-based study

A dynamic microscopic traffic flow simulation within a ring arterial context was developed to investigate the effects of access point spacing on urban arterial flow under a right-in-right-out access management system. The microscopic traffic flow model, centered on car-following and lane-changing behaviors, was established based on vehicle interactions. The car-following aspect encompasses free driving, car-following behavior, and deceleration and braking states while lane-changing considerations include decision-making and acceptable gap assessment. Experimental scenarios account for arterial traffic density, access traffic demand intensity, average access point spacing, and variation coefficient of access point spacing. The traffic flow and speeds within the ring arterial were evaluated across 5040 operational conditions (equating to 5880 simulation hours). The traffic flow trends and speed variations with density across different access spacing scenarios were analyzed. We made an intriguing discovery: the impact on arterial traffic flow increases with larger average access point spacing, challenging conventional traffic planning recommendations that advocate for greater spacing. Additionally, access traffic minimally affects the overall arterial flow when arterial traffic volume is low. By highlighting these critical insights, this study introduces novel considerations for designing and managing access points.

Research on thermal-solid coupling behavior of drum brake under emergency braking on slopes

Abstract When a truck makes emergency braking while driving on a slope, the transient impact force generated can easily cause personal injury to passengers and damage the vehicle’s braking system. In order to study the working state of the brake under this working condition, the ANSYS finite element thermal-solid coupling transient analysis method was used to establish the mechanical model and finite element model of the vehicle and brake under the slope emergency braking state, showing the temperature field and stress field distribution rules and interactions of the drum brake under this working condition, and compared with the flat road emergency braking condition. The results show that the maximum temperature of the brake reaches 184.26°C during emergency braking, and the stress field and temperature field are strongly coupled in two directions, which can easily lead to uneven wear of the linings and a reduction in the fatigue life of the brake.

Prediction of brake pad wear and remaining useful life considering varying vehicle mass and an experimental holistic approach

Estimation of passenger car brake pad wear is considered, including real-time mass estimation to account for variations in vehicle mass. A longitudinal dynamics model is used to estimate mass, the application of the brakes, and a longitudinal braking force. Wear is modelled from brake work based on the product of the braking force and distance travelled during braking. Data is provided by standard vehicle on-board diagnostics data and a sensor fusion based on an inertial measurement unit and satellite position data, sampled from a single car with 10,200 km of on-road driving, including 31 brake pad wear measurement samples, and driving with up to 23% increased vehicle mass. The mass is accurately estimated within ±5% of the actual. Braking states determined from comparisons of measured and modelled deceleration provide accuracies of ≈91%, precisions of ≈96%, and recall rates of ≈86%, with inclusion of varying mass only resulting in minor differences. Brake work is estimated with (a) constant mass, (b) estimated mass, (c) actual mass, and (d) actual mass and braking states. Compared to (a), (b) and (c) provide 9% and 11% increased work, while (d) provides an increase of about 5% compared to (c). Wear coefficients are fitted on the initial half of the wear data considering (a), (b), and (d). Here (a) and (b) provide similar wear rates of k≈−1.22 mm/GJ, while (d) is about 5% lower. Validating on the second half of the data, (b) and (d) provide very similar wear estimates, with overall lower errors than (a). At the final sample, however, (a) provides a slightly lower absolute error, overestimating the wear by about 2%, while (b) and (d) underestimate it by about 3%. RUL, in terms of distance, is estimated across about 9,500 km of data by estimating a running ratio between cumulated work and distance. Here only (a) and (b) are considered, with (a) overestimating the RUL by 600 km at the actual wear limit, while (b) underestimates it by 190 km. A distance-based model is also considered, resulting in a constant RUL error of about 2,000 km.

Research on the Multi-Mode Composite Braking Control Strategy of Electric Wheel-Drive Multi-Axle Heavy-Duty Vehicles

Electric wheel-drive multi-axle heavy-duty vehicles have the characteristics of strong maneuverability and good passability, thereby they are widely used in heavy equipment transportation. However, current research on the composite braking of multi-axle heavy-duty vehicles is rare, which is not conducive to improving braking performance and braking energy utilization efficiency. This work proposes a multi-mode composite braking control strategy for the five-axle distributed electric wheel-drive heavy-duty vehicle. Firstly, given the differences in braking dynamics between two-axle vehicles and multi-axle vehicles, the brake dynamics characteristics of multi-axle vehicles are analyzed, and the vehicle dynamics model of multi-axle vehicles is constructed. Next, a multi-mode composite braking control strategy including a fully electric braking state and hybrid electro–hydraulic braking state is proposed in order to improve the braking energy recovery and braking stability. Finally, a hardware-in-the-loop simulation system is established, and the single-braking conditions and China heavy-duty commercial vehicle test cycle-heavy truck (abbreviated as CHTC-HT) are conducted to verify the performance of the braking control strategy. The results indicate that the recaptured braking energy and braking stability are significantly increased by applying the control strategy proposed in this work.

Study on the interlayer critical response of asphalt pavement with different paving methods based on cohesive zone model

ABSTRACT Different paving methods of asphalt layers are the important factors that affect the interlayer performance and mechanical response of asphalt pavement structure. In order to further analyse the influence of different paving methods on the mechanical properties of asphalt structural layers, four kinds of asphalt pavement with different paving methods were selected as the research objects, namely continuous paving, discontinuous paving (tack coat), discontinuous paving (tack coat + dust), discontinuous paving (no tack coat). Firstly, the interlayer adhesion of asphalt pavement with different paving methods was studied by using the cohesive zone model (CZM). Secondly, different braking modes were selected to apply loads on asphalt pavement to explore the changing law of mechanical response of asphalt pavement under different braking modes. The test results show that the asphalt pavement with continuous paving has the strongest resistance to interlayer adhesion failure, while the asphalt pavement with discontinuous paving (no tack coat) has the weakest resistance to interlayer adhesion failure. In the braking state, the interlayer adhesion of the leading edge of the wheel track on asphalt pavement is most likely to fail, while the trailing edge of the wheel track is most likely to produce the transverse crack.

A Novel Bilevel Electromechanical Compound Braking Coordinated Control Strategy for Electric Vehicles

Due to the difference of response time and braking type between the motor and the pneumatic braking system, it is still difficult to coordinate the motor braking and the pneumatic braking to ensure the vehicle stability and maximal energy regeneration. To address this challenge, a bilevel electromechanical compound braking coordinated control strategy for electric vehicles is proposed considering general and emergency braking state. First, in general braking state, considering the delay characteristics of the pneumatic braking system, a Lagrange quadratic interpolation prediction algorithm is designed to start the pneumatic braking system in advance. Second, in emergency braking state, a model predictive control method is proposed to optimize the braking torque distribution while controlling the wheel slip ratio in a stable range. In order to obtain the optimal control effect, a modified adaptive cuckoo search algorithm is put forward, in which three adaptive impact factors are added. Finally, the proposed control strategy is verified under three road conditions and compared with the conventional control strategy. The results demonstrate significant improvements under gravel road condition, including a 7% increase in energy recovery efficiency, a 92.1% enhancement in the following effect of pneumatic braking torque, and a 43.5% reduction in wheel fluctuation.

Control strategy optimization of hybrid electric vehicle for fuel saving based on energy flow experiment and simulation

Energy flow analysis is one of the most effective methods for assessing and improving vehicle efficiency. It can provide the most effective support for the development and optimization of a hybrid electric vehicle (HEV) control strategy for improving the performance and energy saving of HEVs. In this study, an energy flow experiment of a series–parallel HEV is conducted in a climate chamber under the Worldwide Light-duty Test Cycle to address high fuel consumption. Then, GT-Suite and MATLAB/Simulink co-simulation models for the tested vehicle are built and calibrated. The problems of the original HEV control strategy are addressed using the analysis of vehicle energy flow distributions, operating conditions, and energy efficiency of key parts. Then, two optimized vehicle control strategies (termed Opt1 and Opt2) are employed to test vehicle fuel savings using a calibrated co-simulation model. The specific optimized vehicle control strategies primarily include canceling the series and parallel charging in the braking state, adding the engine direct-drive mode, and reducing the proportion of the parallel mode. The simulated results show that the 100 km fuel consumptions of Opt1 and Opt2 are reduced by 7.1% and 7.5%, respectively, compared with the original vehicle. The proportion of energy that drives the vehicle directly through the engines of Opt1 and Opt2 is increased from 45.7% to 70.2% and 61.6%, respectively. The total vehicle energy losses for Opt1 and Opt2 decrease from 29.0% to 22.5% and 22.9%, respectively. Although the engine of the original vehicle exhibits high thermal efficiency, the efficiency of the entire powertrain system is the lowest, resulting in the highest fuel consumption.

Numerical investigation of inlet distortion in a jet engine coupled with Ski-jump of carrier-based aircraft

Contract with land-based aviation, the ski-jump of carrier-based aircraft is confronted with complicated aerodynamic circumstances. More especially, the occurrence of inlet distortion in the aero-engine would endanger its flight safety. This study conducted the inlet distortion of the aero-engine coupled with the ski-jump of carrier-based aircraft by means of numerical simulation. The movement of the aircraft has been characterized by the nested dynamic grid and user-defined function (UDF). The results show that the inlet distortion of the aero-engine has resulted from the suction of high-temperature exhaust gas from the auxiliary intake grille primarily and the aero-engine inlet subsequently. the presence of an intersection angle between the aircraft axis and carrier axis has brought the accumulation of the high-temperature exhaust gas near the left engine while the sucking of flow into the right engine is ‘fresh air’ in the ambiance. Correspondingly, the inlet distortion of the left engine is larger than that of the right engine. For the braking state, the region-averaged relative temperature rises at the AIP section increased by 27.46% compared with the land case. For the slip-jump, the temperature and pressure distortion at the AIP section decreases rapidly with the increase of the slip-jump distance. After the slip-jump distance is greater than 6m, the total temperature and total pressure distortion almost disappeared. The increase in aircraft height, the velocity magnitude of relative wind velocity, and the distance from the take-off point to the Jet Blast Deflector decreased the inlet distortion of the aero-engine. The relative wind from the left wing (α<0°) brought more inlet distortion to the right engine while the relative wind from the right wing (α>0°) brought more inlet distortion to the left engine. The results obtained in this study are significant because they provide the physical mechanism of inlet distortion of aero-engine and can be used for the guidance of the operational safety of carrier-based aircraft.

Calculation and analysis of fluid-solid coupling of rocket sled supersonic water bucket braking process

In order to solve the problem of structural damage during the braking process of a rocket sled supersonic water bucket, which affects the braking effect, it is proposed to use the FEM fluid-solid coupling calculation technology to analyze the process of the water bucket entering the water brake. The fluid-solid coupling calculation results show that the limit braking state After the water bucket enters the water brake for 0.06ms, the stress at the entrance position exceeds the yield limit of the material, and the structure is severely deformed and damaged; under normal braking conditions, the water bucket enters the water brake for 0.4ms, the plate at the entrance of the bucket bends, and the structure is seriously deformed at 2ms, The structure is destroyed at 3ms. Using the penalty function fluid-structure coupling method, the numerical analysis of the model water bucket was carried out under two working conditions. Due to the unreasonable design of the bucket, the bucket entrance deformed and destroyed during braking. It is recommended to increase the structural strength of the water inlet side plate.

The transitional states of a floating wind turbine during high levels of surge

With the deployment of floating offshore wind turbines, the effect of their wind- and wave-induced platform motion on the turbine’s performance and life is of concern and requires low-order models to develop appropriate control strategies. This work focusses on platform surge as one of the main additional degrees of freedom. The aerodynamic behaviour during the rotor’s transition into propeller state is explored by assessing the spanwise and rotor-integrated aerodynamic forces on the rotor of the NREL 5 MW turbine through a 3D URANS CFD simulation. The CFD findings are compared with a modified actuator disk (AD) theory and 2D Blade-Element Momentum (BEM) approach. In addition to propeller state, where both rotor torque and thrust are negative, two other states were observed with opposite signs of torque and thrust: a braking state, with negative torque but positive thrust, and the second a quasi-windmill state with thrust negative yet torque positive. The results demonstrate that BEM coupled with AD can reliably predict the transitions to these states during such high levels of platform surge and give hints to how the underpinning force balances are affected by temporal perturbations.

A Dynamic Load Simulation Algorithm Based on an Inertia Simulation Predictive Model

In this study, an electric dynamic load simulation system (EDLSS) algorithm was proposed based on an inertia simulation predictive model to mitigate strong-coupling torque disturbance and load torque fluctuation caused by the change in the motion state of a bearing system. First, the inertia simulation model was proposed by combining the dynamic equations of both the EDLSS and the target system. The aforementioned inertia simulation model converted the conventional realisation method of the inertia simulation into the tracking of the motion characteristics for the target system under the same working conditions. Next, based on the aforementioned inertia simulation model while considering the strong-coupling torque effect and motor braking state disturbance as two influential factors, an inertia simulation predictive model and a load simulation algorithm were proposed. The predicted speed calculated by the predictive model was consistent with the dynamic characteristics of the target system under the same working conditions and input into the control loop. Based on the analysis of the braking state and power model of the permanent magnet synchronous motor, an energy feedback control method was proposed to improve EDLSS stability caused by the braking state of the loading motor. Finally, the experimental data revealed that the maximum speed fluctuation range of the loading motor was approximately 7.5, which was 84% lower than the range before the application of the aforementioned algorithm, which was about 46.8. Furthermore, the maximum range of the torque ripple was close to 1.5, which was 75% lower than before, which was roughly 6. All experimental data were consistent with simulation data.

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.

Control strategy of hybrid energy storage in regenerative braking energy of high-speed railway

Regenerative braking energy (RBE) will be generated when high-speed train is in braking state, but the utilization rate of RBE is generally low. To solve this problem, based on the hybrid energy storage system (HESS), a scheme for energy storing and utilizing high-speed train RBE is proposed. In this scheme, the HESS is connected to the railway traction power supply system through the railway power conditioner (RPC) as the interface circuit. The control strategy of energy storage RPC is proposed by analyzing the compensation principle, then the power of two energy storage media is allocated. The effectiveness of the scheme is verified by simulation. The findings of the research suggest that the control strategy of energy storage RPC can not only effectively utilize RBE generated by high-speed train, but also improve the power quality and extend the service life of energy storage system.

Stability analysis of the anti-lock braking system with time delay

A time delay exists between driver input and vehicle braking state response during the working process of the anti-lock braking system (ABS), and the braking performance of vehicles will be further reduced due to the delay of controllers. This paper investigates a systematic method of stability analysis for time delay ABS, and the analysis focuses on the stability and critical delay algorithm of ABS with delay time. Firstly, the dynamic structure and modelling process of ABS are briefly introduced, and PD control algorithm is adopted to improve the control performance. Then, dynamic models of ABS with time delay are derived, and the full delay stability interval and critical time delay algorithm of ABS are deduced by using the generalized Sturm criterion method. Finally, the validity of the critical delay algorithm by the proposed method and the stability and accuracy of ABS with time delay, different road conditions, vehicle speeds and control parameters are illustrated by numerical simulations, and the results show that the critical time delay algorithm of ABS can be verified under different conditions.

Research on control strategy of electric vehicle under braking state based on fuzzy control

Aiming at how to improve the efficiency of pure electric vehicles in the process of braking energy recovery and security problems, this paper takes brake laws ECER13 curve and ideal braking force distribution curve as constraint conditions, to design a kind of input is braking intensity z, battery SOC charge ratio, output for mechanical brake than kp, electric braking is larger than that of ki fuzzy control strategy, and with the fuzzy control strategy as the core to establish the model of regenerative braking, this model embedded in the ADVISOR of pure electric vehicles in the model, and the simulation under the condition of circulating CYC_UDDS. The results show that under the fuzzy control strategy, the effective recovery rate of regenerative braking energy increases by 5.4%, and the energy utilization rate of the vehicle increases by 1.9%.

Structural simulation analysis of a certain vehicle type disc brake based on ANSYS Workbench

Taking the disc brake as the research object, the three-dimensional model established by Solidworks is imported into ANSYS Workbench, and its strength and modal simulation analysis are carried out. Taking the disc brake as the research object, the 3D model established by SolidWorks is imported into ANSYS Workbench, and the strength and modal simulation analysis are carried out then. Using the maximum stress point and maximum deformation position under the emergency braking state, combined with the results of modal analysis cloud chart, the resonance range is verified by comparing with the natural frequency, which provides reference for the actual tests and structural improvement.

A traffic prediction model based on multiple factors

Traffic prediction is a vital part of intelligent transportation systems. The ability of traffic risk prediction is of great significance to prevent traffic accidents and reduce the damages in a proactive way. Because of the complexity, uncertainty and dynamics of spatiotemporal dependence of traffic flow, accurate traffic state prediction becomes a challenging issue. Most neural networks are compute intensive and memory intensive, making them hard to deploy on embedded systems with limited hardware resources. A real-time and high-compressed video object detection structure is proposed. For traffic prediction, many previous studies only explore the utility of a single factor in their prediction and a few multi-factor researches are conducted. Other studies focus on the temporal distribution of traffic flow, ignoring the spatial correlation. And some methods based on graph convolutional networks (GCNs) do not consider the dynamics of graph structure which is a crucial factor to traffic prediction. In this paper, we analyze and process the onboard video captured by the dashboard camera real time. A high accurate deep learning model called varying spatiotemporal graph-based convolution model (VSTGC) is proposed to express the spatiotemporal structures and forecast future traffic safety trends from previous traffic flow. The traffic detailed features (such as vehicle type, braking state, whether changing lanes or not) and external variables (such as weather, time and road condition) are extracted from our big datasets. We conduct extensive experiments to evaluate the VSTGC model on real-world traffic datasets. Experiments on our real traffic dataset show that the proposed model performs competitive performances over the other state-of-the-art approaches.

STMAG: A spatial-temporal mixed attention graph-based convolution model for multi-data flow safety prediction

Spatiotemporal safety forecasting has various applications in the neuroscience, climate and transportation domains. It is challenging due to (1) the complex spatial dependency on networks, (2) non-linear temporal dynamics with changing conditions and (3) the inherent difficulty of long-term forecasting. To address these challenges, a safety prediction model called the Spatial-Temporal Mixed Attention Graph-based Convolution model (STMAG) is proposed. Specifically, STMAG captures spatial dependency using graph convolutional networks (GCN), and temporal dependency using the sequence-to-sequence (Seq2Seq) architecture with the mixed attention mechanisms. A case study on the implementation of this model in traffic safety prediction is given as an example. Traffic safety forecasting is one canonical example of such a learning task, which is also a crucial problem to improving transportation and public safety. A number of detailed features (such as vehicle type, braking state, whether changing lanes or not) and exogenous variables (such as weather, time and road condition) are extracted from our big datasets. Finally, we conduct extensive experiments to evaluate the STMAG framework on real-world large-scale road network traffic datasets. Extensive experiments on our dataset show that the STMAG framework makes reasonably accurate predictions and significantly improves the prediction accuracy over baseline approaches.

A roller-skating/walking mode-based amphibious robot

An amphibious spherical robot capable of motion on land as well as underwater is developed to implement the complicated underwater operations in our previous research. In order to improve the speed performance of the spherical robot on a slope or comparatively smooth terrains, we propose a new roller-skating mode for the robot by equipping a passive wheel on each leg to implement the roller-skating motion in this paper. A braking mechanism is designed to transform the state of each passive wheel between free rolling and braking states by compressing and releasing the spring, which is controlled by the vertical servo motor on each leg. Besides, in order to improve the walking stability of the wheeled robot in longitudinal direction, a closed-loop control method is presented to control the stability of the direction of movement while walking. Therefore, we conduct the experiments on smooth terrains and down a slope to evaluate the performance of the roller-skating motion, including gait stability and velocity. Finally, plenty of walking experiments are conducted to evaluate the ability of directional control. We describe a roller-skating/walking mode-based quadruped amphibious robot.The new wheeled robot has two on-land actuating modes: walking and roller-skating.A braking mechanism installed on each leg is proposed to apply brake for the robot.The mechanism is also used as a transformation mechanism for mode switching.We present a closed-loop control method to control the direction of movement.

Research on switched reluctance machine drive topology and control strategies for electric vehicles

The electric drive system is one of the key technologies for electric vehicles. First, the energy flow of an electric vehicle is analyzed in the driving, braking, and charging working states. After that, a drive topology that can achieve 3 working states is proposed based on the driving characteristics of a switched reluctance machine. In the driving state, the boost mode of a front-end converter is used to achieve different operating conditions, including low speed with a light load or high speed with a heavy load. In the braking state, the front-end converter is used to implement smooth switching between initial excitation and braking energy feedback. In the charging state, a new power factor correction circuit is proposed, and the motor windings and power converter constitute the onboard charger, whose power factor is correctable. According to the proposed drive topology, the control strategies for 3 working states are put forward. Finally, an experimental platform is built to verify the correctness of the control strategies as well as the flexibility of the whole system.