Vehicle distance estimation using a mono-camera for FCW/AEB systems

For robust vision-based forward collision warning (FCW) and autonomous emergency braking (AEB) systems, not only reliable detection performance including high detection rate and low false positives but also accurate measurement output of a target vehicle is required. Especially, in order to reduce false alarm or activation of FCW/AEB systems, the systems require the precise measurement output of a target object, such as position, velocity, acceleration, and time-to-collision (TTC). In this study, we developed a measurement estimation algorithm of a target vehicle using a monocular camera. This method estimates two cases of vehicle widths for a target vehicle by using the detected lane information and a pin-hole camera model. After that, the position, velocity, acceleration, and TTC of a target vehicle are estimated by using a Kalman filter for the each estimated vehicle width. To improve robustness, the both estimation results using the detected lane information and the pinhole camera model are fused. This estimation algorithm was evaluated and compared with the state-of-the-art technology. As a result, the proposed measurement output estimation method can improve the performance of the FCW/AEB systems.     

Effects of Injection Timing on Transient Performance of A Regulated Two-Stage Turbocharged Diesel Engine with Turbine Bypass Valve

The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NO_X emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance.     

软土地层顶管法地下通道近接桥梁施工保护方案研究

为顶管施工中既有桥梁结构的保护提供合理可行的方案,以昆明市轨道交通4 号线菊华站地铁车站过街通道矩形顶管近接高架桥施工为背景,采用数值模拟的方法,对软土地层顶管法地下通道近接桥梁施工的地层注浆预加固及不同触变泥浆减摩等保护方案的应用效果进行研究。研究结果表明: 1)对桥桩桩侧土进行预加固可以明显减小顶管施工过程中桥桩的水平横向变形,减小比例达34%; 2)采用超灌触变泥浆减摩方案,可有效降低顶管顶进时管土摩擦力对桥桩的影响,其中桥桩纵向变形的最大值在采用超灌触变泥浆减摩方案时,相较于常规触变泥浆减摩方案减小28%; 3)采用桥桩桩侧土预加固结合超灌触变泥浆减摩的方案,可保证顶管施工过程中近接桥梁结构的安全。     

应对突发大规模流行病的城市常规公交管控策略

公共交通内部相对狭小和密闭的空间，使得乘客间频繁发生近距离接触，是流行病扩散的高危环境。面对诸如新型冠状病毒肺炎这类突发大规模流行病时，交通管理者通常采取的方案是全部公交线路停运，彻底阻断流行病通过公共交通系统传播这一个途径，但是对于公交乘客而言，如果缺乏替代的出行方式，将严重降低其移动性，甚至会影响其基本的生活条件。利用北京市公交IC卡刷卡数据，挖掘乘客的个人出行特征和相互之间的接触特征，构建公交乘客动态接触网络，试验数据统计显示北京公交乘客单次出行与他人的平均接触时间为17 min，通勤乘客工作日与他人平均累计接触123次。利用理论传播模型（SEI和SIS）模拟流行病在公共交通系统内的扩散，对比随机网络分析其特征，发现公交乘客间接触的周期性发生规律显著促进了流行病的快速传播。将乘客传播影响力集计至公交线路，针对常规公交网络设计停运部分线路的运营方案，使用站点间平均邻接距离作为指标，衡量部分停运方案导致的常规公交系统可达性损失。研究对比了停运方案实施前后的流行病扩散规模。研究结果表明，只需要停运小部分线路就能使流行病暴发得到遏制，同时公交系统的整体可达性没有明显下降。     

Iterative Learning Control Algorithm for Feedforward Controller of EGR and VGT Systems in a CRDI Diesel Engine

The modern diesel engines equip the exhaust gas recirculation (EGR) system to suppress the NOx emissions. In addition, the variable geometric turbocharger (VGT) system is installed to improve the drivability and fuel efficiency. These EGR and VGT systems have cross-coupled behavior because they interact with the intake and the exhaust manifolds. Furthermore, the turbocharger time delay, gas flow dynamics through EGR pipe cause the nonlinearity characteristics. These nonlinear multi-input-multi-output characteristics cause the degradation of control accuracy, especially during the transient condition. In order to improve the control accuracy, this study proposes an iterative learning control (ILC) algorithm for feedforward controller of EGR and VGT systems. The feedforward controller obtains the values about EGR and VGT actuators using the previous control results in predefined transient states. The ILC algorithm consists of a PD-type learning function and a low-pass filter. The control gains of learning function are determined to guarantee the convergence of learning results. In addition, the low-pass filter is designed for robustness against plant disturbance. The proposed control algorithm was validated by engine experiment which repeated predefined transient states. The error was reduced by 15 % according to the gain. As a result, the proposed algorithm is affordable for improving the transient control performance.     

Structural Optimization for Roof Crush Test Using an Enforced Displacement Method

A roof crush test has been utilized to reduce passengers’ injuries from a vehicle rollover. The Federal Motor Vehicle Safety Standards (FMVSS) 216 and the Insurance Institute for Highway Safety (IIHS) perform actual vehicle tests and evaluate the vehicle’s ratings. Nonlinear dynamic response structural optimization can be employed not only for achievement of a high rating but also minimization of the weight. However, the technique needs a huge computation time and cost because many nonlinear dynamic response analyses are required in the time domain. A novel method is proposed for nonlinear dynamic response structural optimization regarding the roof crush test. The process of the proposed method repeats the analysis domain and the design domain until the convergence criteria are satisfied. In the analysis domain, the roof crush test is simulated using a high fidelity model of nonlinear dynamic finite element analysis. In the design domain, a low fidelity model of linear static response structural optimization is utilized with enforced displacements that come from the analysis domain. Correction factors are employed to compensate the differences between a nonlinear dynamic analysis response and a linear static analysis response with enforced displacement. A full-scale vehicle problem is optimized with a constraint on the rigid wall force from the analysis in the design domain.     

基于VW-PCA的盾构刀盘驱动液压系统故障诊断

为提高盾构刀盘液压系统故障诊断的快速性和准确性,引入权值向量来改进传统主元分析法（PCA）,并推导变量加权主元分析法（VW-PCA）公式。通过AMESim仿真软件建立6 450 mm土压平衡盾构刀盘驱动液压系统模型,选取12个测试变量,模拟仿真6种故障状态; 运用仿真故障数据得到每一类故障的加权向量,建立变量加权主元分析模型（VW-PCA）,并使用该模型对测试故障样本进行研究。结果表明： 变量加权(VW) 能够增强各系统变量对不同故障类型的贡献程度,变量加权主元模型（VW-PCA）能够显著提高系统诊断的正确率,最大可提高50%以上。     

软岩隧道初期支护沉降机理及其工程措施研究

为解决软岩隧道开挖过程中初期支护整体下沉普遍较大的工程难题,依托郑州至西安高速铁路大断面黄土隧道及成昆铁路第三系昔格达地层软弱围岩隧道工程,通过理论计算及现场实测,对软弱围岩隧道初期支护普遍沉降较大的原因以及采取的工程措施的可靠性进行分析,得到以下成果： 1）软弱围岩隧道下沉量往往超过20 cm,现场实测的拱脚承受最大荷载为897.4 kN,初期支护整体下沉大的主要原因是拱脚压力较承载力大一个数量级; 2）锁脚锚杆靠近钢架位置的轴力最大,为55 kN。大拱脚的承压特性显著,其压力极值达到0.9～1.7 MPa; 3）增设锁脚锚杆（管）、扩大拱脚和及时闭合仰拱是控制软岩隧道初期支护沉降的关键措施。     

基于玻璃纤维锚杆微应变测试的软岩隧道松动圈测试技术及应用

为解决软弱破碎围岩地层隧道松动圈测试的难题,分析现有松动圈测试技术现状,以全长黏结型玻纤锚杆为载体,提出一种适用于破碎软岩隧道的围岩松动圈测试技术。该测试技术以锚杆微应变变化趋势为基础,结合锚杆中性点理论,可大致确定围岩松动圈范围。将该技术应用在大（理）临（沧）铁路杏子山隧道破碎炭质板岩大变形地段进行验证,结果表明： 全长黏结型玻璃纤维锚杆在松动区可与软弱破碎围岩有效协调变形,锚杆微应变变化趋势与中性点理论相符,采用锚杆微应变变化趋势表征围岩松动圈范围合理可行。同时该技术测试精度可通过调整沿锚杆长度粘贴应变片的密度来控制,有效弥补传统物探松动圈测试技术对岩体要求高的问题,在软弱破碎围岩地层中具有较好的操作性和适用性。