Target Vehicle Selection Algorithm for Adaptive Cruise Control Based on Lane-changing Intention of Preceding Vehicle

To improve the ride comfort and safety of a traditional adaptive cruise control(ACC)system when the preceding vehicle changes lanes,it proposes a target vehicle selection algorithm based on the prediction of the lane-changing intention for the preceding vehicle.First,the Next Generation Simulation dataset is used to train a lane-changing intention prediction algorithm based on a sliding window support vector machine,and the lane-changing intention of the preceding vehicle in the current lane is identified by lateral position offset.Second,according to the lane-changing intention and collision threat of the preceding vehicle,the target vehicle selection algorithm is studied under three different conditions:safe lane-changing,dangerous lane-changing,and lane-changing cancellation.Finally,the effectiveness of the proposed algorithm is verified in a co-simulation platform.The simulation results show that the target vehicle selection algorithm can ensure the smooth transfer of the target vehicle and effectively reduce the longitudinal acceleration fluctuation of the subject vehicle when the preceding vehicle changes lanes safely or cancels their lane change maneuver.In the case of a dangerous lane change,the target vehicle selection algorithm proposed in this paper can respond more rapidly to a dangerous lane change than the target vehicle selection method of the traditional ACC system;thus,it can effectively avoid collisions and improve the safety of the subject vehicle.

Modelling of vehicle interaction behavior during discretionary lane-changing preparation process on freeway

In order to increase the accuracy of microscopic traffic flow simulation,two acceleration models are presented to simulate car-following behaviors of the lane-changing vehicle and following putative vehicle during the discretionary lanechanging preparation( DLCP) process, respectively. The proposed acceleration models can reflect vehicle interaction characteristics. Samples used for describing the starting point and the ending point of DLCP are extracted from a real NGSIM vehicle trajectory data set. The acceleration model for a lanechanging vehicle is supposed to be a linear acceleration model.The acceleration model for the following putative vehicle is constructed by referring to the optimal velocity model,in which optimal velocity is defined as a linear function of the velocity of putative leading vehicle. Similar calibration,a hypothesis test and parameter sensitivity analysis were conducted on the acceleration model of the lane-changing vehicle and following putative vehicle,respectively. The validation results of the two proposed models suggest that the training and testing errors are acceptable compared with similar works on calibrations for car following models. The parameter sensitivity analysis shows that the subtle observed error does not lead to severe variations of car-following behaviors of the lane-changing vehicle and following putative vehicle.

The Effect of Lateral Offset Distance on the Aerodynamics and Fuel Economy of Vehicle Queues

The vehicle industry is always in search of breakthrough energy-saving and emission-reduction technologies.In recent years,vehicle intelligence has progressed considerably,and researchers are currently trying to take advantage of these developments.Here we consider the case of many vehicles forming a queue,i.e.,vehicles traveling at a predetermined speed and distance apart.While the majority of existing studies on this subject have focused on the influence of the longitudinal vehicle spacing,vehicle speed,and the number of vehicles on aerodynamic drag and fuel economy,this study considers the lateral offset distance of the vehicle queue.The group fuel consumption savings rate is calculated and analyzed.As also demonstrated by experimental results,some aerodynamic benefits exist.Moreover,the fuel consumption saving rate of the vehicle queue decreases as the lateral offset distance increases.

Adaptive Backstepping Control for Hypersonic Vehicles with Actuator Amplitude and Rate Saturation

This paper presents a constrained control strategy for the hypersonic vehicle with actuator amplitude,rate constraints and aerodynamic uncertainties.First,a vehicle-actuator control model is derived in consideration of actuator dynamics properties explicitly.Second,a nonlinear disturbance observer is designed to estimate the aerodynamic uncertainties,and then an adaptive backstepping control technique is adopted with a modified first-order-filter to eliminate the“explosion of terms”problem.Next,for handling the actuator amplitude and rate constraints,a novel auxiliary compensation system is constructed to generate quickly compensating signals to ensure tracking performance of command signal.By the Lyapunov stability proof,the proposed control scheme can enssure that the tracking errors converge to an arbitrarily small neighborhood around zero when the actuator constraints and aerodynamic uncertainties exist.Finally,numerical simulations are implemented to illustrate the effectiveness of the proposed control method.

Nonlinear instability suppression of closed-loop pilot-vehicle system with rate-limiting actuator based on anti-windup compensation

To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensation method to avoid category II PIOs is investigated. Firstly, the AW compensation method originally used for controlling input magnitude limited system is introduced, then this method is extended for controlling input rate-limiting system through a circle criterion theorem. Secondly, the establishment of the AW compensator is transformed into the solving of linear matrix inequalities. Finally, an AW compensator establishment algorithm for the closed-loop pilot-vehicle system with the rate-limiting actuator is obtained. The effectiveness of the AW compensation method to avoid category II PIOs is validated by time-domain simulations,and compared with rate-limited feedback（RLF） command rate compensation method. The results show that the AW compensation method can effectively suppress category II PIOs and maintain the nominal performance when the closed-loop pilot-vehicle system is normal. Unlike the command rate compensator which works upon system uninterruptedly, the AW compensation method affects the closed-loop pilot-vehicle system only when the rate-limiting of actuator is activated, so it is a novel PIO avoidance method.

Effects of the profile of a supercavitating vehicle's front-end on supercavity generation

The authors designed three different front profiles for supercavitating vehicles based on cavity theory and the Granville streamlined equation are designed. Experiments were done using these front profiles in the Northwestern Polytechnical University high-speed water tunnel. The experiments indicated that the critical volume of gas required for supercavitation is affected by the axial distribution of the front-end＇s slope. The experimental data showed critical gas flow rates required for the three designs were less than rood-l, with the greatest decrease 24%. The experimental results also showed the supercavitation generation speeds of the models were faster than mod-1 by up to 32.4%. This verifies that the front profile of a supercaviting vehicle effects supercavity generation speed and critical gas flow rates. The smaller the changes in axial distribution of pressure, the higher the supercavity generation speed. The smaller the changes in curvature distribution of axial, the smaller the critical gas flow rates.

Prescribed performance neural control to guarantee tracking quality for near space kinetic kill vehicle

A prescribed performance neural controller to guarantee tracking quality is addressed for the near space kinetic kill vehicle (NSKKV) to meet the state constraints caused by side window detection. Different from the traditional prescribed performance control in which the shape of the performance function is constant, this paper exploits new performance functions which can change the shape of their function according to different symbols of initial errors and can ensure the error convergence with a small overshoot. The neural backstepping control and the minimal learning parameters (MLP) technology are employed for exploring a prescribed performance controller (PPC) that provides robust tracking attitude reference trajectories. The highlight is that the transient performance of tracking errors is satisfactory and the computational load of neural approximation is low. The pseudo rate (PSR) modulator is used to shape the continuous control command to pulse or on-off signals to meet the requirements of the thruster. Numerical simulations show that the proposed method can achieve state constraints, pseudo-linear operation and high accuracy.

A remote sensing system of vehicle emissions based on tunable diode laser technology

As being an effective real-time method of monitoring vehicle emissions on-road, a remote sensing system based on the tunable diode laser （TDL） technology was presented, and the key technologies were discussed. A field test in Guangzhou（Guangdong, China） was performed and was found that the factors, such as slope, instantaneous speed and acceleration, had significant influence on the detectable rate of the system. Based on the results, the proposal choice of testing site was presented.

Research on TDM approach of sharing BRT-lane supported by vehicle-infrastructure integration

In order to increase the availability of the part-time idle bus rapid transit lane(BRT-lane),a time division multiplexing(TDM) method to share BRT-lane with the vehicles besides BRT buses is proposed based on vehicle-road collaboration. The TDM control strategy is established under the circumstance of vehicle-infrastructure integration(VII). The algorithm is given to forecast the segmented BRT travel time. According to the real time traffic information,a comprehensive model is given to estimate the vehicles' lane-changing time from/to the BRTlane to/from its neighbor lane and determine the timing sequence for vehicles collaboration. Finally,the experiment demonstrates that the predicted value of the travel time and lane-changing time is much close to the true value. The control strategy of the vehicles collaboration could promise the non-BRT vehicles to share BRT-lane without disturbing BRT's priority.

Localization and Evaluation of Motor Vehicle Emission Simulator (MOVES) Model for Predicting the Emissions of Private Cars:a Case Study of Shenzhen City,China

Motor Vehicle emission simulator(MOVES)model was localized by changing the base emission rates in MySQL database of the model,and using the actual measured data for private cars in Shenzhen City,China.The performances of localized MOVES model and non-localized MOVES model were evaluated by comparing the predicted emission factors to the measured ones.The results showed that by localization of the base emission rates,the prediction accuracy of the localized MOVES model for hydrocarbon(HC)and nitrogen oxides(NO x)was significantly improved.The accuracy of the localized MOVES model simulations in the Opmode increased by 86%,88%and 71%for HC,76%,42%and 72%for NO x on arterial roads,expressways and highways.For carbon monoxide(CO),however,the simulation performance based on the average velocity mode on expressways and highways became poor after localization,with the decrease of 28%and 8%respectively.Overall,by the localization of the base emission rates,the relative errors of the simulated emission factors of HC,CO and NO x of private cars were less than 37%.

Carbon dioxide levels and ventilation for running vehicle

Factors contributing to ventilation quantity of the vehicle are ventilation modes, cabin characteristics and vehicle speeds. CO2 levels were investigated under different speeds and ventilation modes. Four modes were selected： A： vent closed and fan shut, B： vent closed and fan started, C： vent opened and fan shut, D： vent opened and fan started. In vent closed modes, CO2 levels reached several thousands of ppm in few minutes at any speeds. For mode C, CO2 levels exceeded the guideline at low speeds 50 km/h, while it reduced below one at higher speeds 80 km/h. Fan has no significant impact on ventilation during vent closed. The ventilation efficiency in each mode increased with the speed raising. To determine the ventilation rate of running vehicle, the experiment was implemented by using CO2 emitted from driver and passengers as tracer gas. Ventilation rate for the different modes and speeds were calculated.

Optimal trajectory and heat load analysis of different shape lifting reentry vehicles for medium range application

The objective of the paper is to compute the optimal burn-out conditions and control requirements that would result in maximum down-range/cross-range performance of a waverider type hypersonic boost-glide(HBG) vehicle within the medium and intermediate ranges,and compare its performance with the performances of wing-body and lifting-body vehicles vis-a-vis the g-load and the integrated heat load experienced by vehicles for the medium-sized launch vehicle under study.Trajectory optimization studies were carried out by considering the heat rate and dynamic pressure constraints.The trajectory optimization problem is modeled as a nonlinear,multiphase,constraint optimal control problem and is solved using a hp-adaptive pseudospectral method.Detail modeling aspects of mass,aerodynamics and aerothermodynamics for the launch and glide vehicles have been discussed.It was found that the optimal burn-out angles for waverider and wing-body configurations are approximately 5° and 14.8°,respectively,for maximum down-range performance under the constraint heat rate environment.The down-range and cross-range performance of HBG waverider configuration is nearly 1.3 and 2 times that of wing-body configuration respectively.The integrated heat load experienced by the HBG waverider was found to be approximately an order of magnitude higher than that of a lifting-body configuration and 5 times that of a wing-body configuration.The footprints and corresponding heat loads and control requirements for the three types of glide vehicles are discussed for the medium range launch vehicle under consideration.

Study on the Impact of Heavy Transport Vehicles Braking System Requirements on Road Safety in Costa Rica

Accidents involving heavy vehicles might show high mortality rates, so it is important to study ways of reducing them. in this research, it was carried out an analysis of the regulations concerning heavy vehicle braking systems in Costa Rica. And some opportunities of improving road safety regarding heavy vehicle braking systems were identified. The analysis showed several regulatory weaknesses, among which were found： lack of regulatory controls of vehicles importation, the friction coefficient associated to maximum braking distance is not specified, the use of technologies that guarantee a stable braking is not compulsory, the measuring procedure of braking efficacy in vehicle inspection shows some deficiencies, and little controls have been established on maintenance practices of heavy vehicle fleets.

An enhanced eco-driving strategy based on reinforcement learning for connected electric vehicles:cooperative velocity and lane-changing control

Purpose–This study aims to propose an enhanced eco-driving strategy based on reinforcement learning(RL)to alleviate the mileage anxiety of electric vehicles(EVs)in the connected environment.Design/methodology/approach–In this paper,an enhanced eco-driving control strategy based on an advanced RL algorithm in hybrid action space(EEDC-HRL)is proposed for connected EVs.The EEDC-HRL simultaneously controls longitudinal velocity and lateral lane-changing maneuvers to achieve more potential eco-driving.Moreover,this study redesigns an all-purpose and efficient-training reward function with the aim to achieve energy-saving on the premise of ensuring other driving performance.Findings–To illustrate the performance for the EEDC-HRL,the controlled EV was trained and tested in various traffic flow states.The experimental results demonstrate that the proposed technique can effectively improve energy efficiency,without sacrificing travel efficiency,comfort,safety and lane-changing performance in different traffic flow states.Originality/value–In light of the aforementioned discussion,the contributions of this paper are two-fold.An enhanced eco-driving strategy based an advanced RL algorithm in hybrid action space(EEDC-HRL)is proposed to jointly optimize longitudinal velocity and lateral lane-changing for connected EVs.A full-scale reward function consisting of multiple sub-rewards with a safety control constraint is redesigned to achieve eco-driving while ensuring other driving performance.

A New Methodology for Reducing Yaw Rate Estimation Error

The dependency of the steady-state yaw rate model on vehicle weight and its distribution is studied in this paper. A speed-dependent adjustment of the yaw rate model is proposed to reduce the yaw rate estimation error. This new methodology allows the calibration engineer to minimize the yaw rate estimation error caused by the different weight conditions without going through the calibration process multiple times. It is expected that this modified yaw rate model will improve the performance of Electronic Stability Control (ESC) systems such as response time and robustness.

Lane-changing decision rule with the difference of traffic flow's variation in multi-lane highway for connected and autonomous vehicles

Drivers are not far-sighted when they execute lane-changing manipulation.To address this issue,this study proposes a rule to improve vehicles'lane-changing decisions with accurate information of surrounding vehicles(e.g.time headway)-More specifically,connected and autonomous vehicles(CAVs)change lanes in advance if they find severer flow reducing in the lanes,while CAVs should maintain the car-following state if the variations of traffc flow in all lanes have a similar trend.To ilustrate the idea,this study frst calibrates two classic car-following models and a lane-changing model,and then conducts numerical simulations to illustrate the short-sighted decision of drivers.The study incorporates the idea into a lane-changing decision rule by changing the lane-changing model's pa-rameter,and conducts numerical tests to evaluate the effectiveness of the lane-changing decision rule in a multi-lane highway with a bottleneck.The results of this study indicate that the new lane-changing decision rule can substantially improve the throughput of the traffic flow,especially when the inflow exceeds the remaining capacity of the road.The lane-changing rule and results can bring insights into the control of CAVs,as well as the driver assistance system in connected vehicles.

9号道岔区铺设减振垫浮置板的行车安全性及舒适性研究

地铁道岔区在基本轨、尖轨处以及道岔钢轨接头处存在大量钢轨不连续地段,轮轨相互作用强烈,轨道系统振动明显,减振垫浮置板轨道作为一种高等减振措施已应用于地铁线路道岔区。为探究减振垫浮置板应用于9号道岔的适用性,并作为减振地段与普通无砟轨道的过渡段的可行性,以某地铁高架9号道岔为研究对象,建立桥上道岔三维有限元模型,仿真分析地铁B型车在120 km/h直向过岔和30 km/h侧向过岔的情况下,列车的行车安全性、舒适性以及轨下结构形变。对比在9号单开道岔区域设置的2种刚度过渡方式的优劣及其减振效果,较为系统地论证了在9号道岔区域铺设减振垫浮置板的可行性。研究结果表明:1)列车通过铺设减振垫浮置板的9号道岔区域时,浮置板位移极值出现在转辙区域和心轨区域,最大位移出现在尖轨位置,可增大尖轨处单板橡胶垫支承刚度,以保证轨道结构变形均匀;2)列车逆向侧向通过设置过渡段的减振垫浮置板道岔区时,2级过渡方式的车体最大垂向加速度、最大横向加速度、最大脱轨系数、最大轮重减载率、轨道刚度变化率以及减振效果等指标均优于1级过渡方式;3)在道岔区铺设减振垫浮置板,列车直向和侧向通过时的行车安全性和舒适性均能满足相关评价指标,且2级过渡方式更优。研究结果可为后续道岔区减振设计研究提供一定的理论参考。

车用液氢气瓶快充过程数值研究

车用液氢气瓶加注过程中,因加注速度快且气瓶容积小,极易造成过充现象,导致安全事故发生。针对设有气包防过充装置的车载液氢气瓶建立三维对称模型,采用CFD方法对气瓶快速加注过程开展数值仿真。分析了开孔孔径、加注速率、初始充满率和防过充装置容积对防过充装置性能的影响规律。结果表明:开孔孔径是影响防过充装置性能的主要因素,其限制了液体的流通能力;采用6 mm孔径和初始充装量为50%的状况下,充装结束后气瓶都将过充,最大充装率可达98.4%;采用大容积的防过充装置可以为气瓶预留更多的气相安全空间,但同时也会导致充装量不足等问题,当防过充装置容积为100 L时,最终充装量仅有77.2%。

冷轧方式与退火温度对无取向硅钢组织、织构及磁性能的影响

以连续式和可逆式冷轧无取向硅钢为研究对象,对其进行退火实验,采用金相显微镜、X射线衍射仪(XRD)表征分析不同冷轧方式无取向硅钢在不同退火温度(920~1070℃)下的组织和织构,探讨轧制方式与退火温度对无取向硅钢磁性能的影响。结果表明:在920~1070℃退火后,连续式冷轧样品平均晶粒尺寸分布在20.7~134.4μm范围,可逆式冷轧样品平均晶粒尺寸分布在17.3~155.5μm范围,随退火温度的提升,2种冷轧方式退火板晶粒总体上均在不断长大;冷轧板织构主要由强的旋转立方织构组成,可逆式和连续式冷轧样品退火板织构以γ纤维和α纤维织构为主,γ纤维织构主要聚集在{111}<112>处,α纤维织构主要聚集在{111}<110>处,γ纤维织构强度随退火温度升高而显著降低,α纤维、Goss和旋转立方织构强度变化很小;可逆式与连续式冷轧板{111}<110>织构强度相近,可逆式冷轧退火板{111}<112>织构强度始终高于连续式冷轧退火板。1040℃退火时,可逆式和连续式冷轧退火板的P_(1.5/50)(50 Hz下,磁感应强度为1.5 T时的损耗)均达最低,分别为2.512,2.445 W/kg;1070℃退火时,可逆式与连续式冷轧退火板的P_(1.5/50)有所增长,最终分别为2.625,2.494 W/kg。随退火温度升高,2种冷轧方式退火板的P_(1.5/50)均先降后升,且连续式冷轧退火板的P_(1.5/50)始终更低、B_(50)更高(磁场强度为5000 A/m时的磁感应强度)。

电动汽车行驶稳定性模型预测控制仿真研究

为了提高电动汽车行驶的稳定性,提出了一种集成的汽车和车轮稳定性控制系统,并对汽车行驶的稳定性控制效果进行仿真。创建电动汽车模型简图,给出电动汽车动力学方程式。采用模型预测控制技术,设计了一种集成的汽车和车轮稳定性控制器。采用MATLAB软件对电动汽车横摆角速度、行驶速度和侧滑角进行仿真,与无模型预测控制器输出结果进行对比。结果显示:采用无模型预测控制器,电动汽车横摆角速度、行驶速度跟踪误差较大,振动幅度较大,产生的侧滑角较大。采用模型预测控制器,电动汽车横摆角速度、行驶速度跟踪误差较小,振动幅度较小,产生的侧滑角较小。采用模型预测控制器,能够提高电动汽车行驶的稳定性,避免汽车在突然转弯时发生侧翻现象。