基于运动学和动力学模型的无人驾驶路径跟踪控制器设计

设计了一种应用于无人驾驶控制的基于车辆运动学和动力学模型的路径跟踪控制器,包括运动学和动力学模型、路径跟踪控制模型、地图匹配模型和执行命令融合模型,使用实时车辆姿态信息进行转向角度预测,使用实时车辆定位信息进行反馈控制以消除系统干扰和模型误差。系统硬件包括车辆平台、嵌入式Mbed开发平台、Ubuntu系统运行平台和惯性导航系统,软件框架使用robotic operation system(ROS),使用rosserial服务连接嵌入式Mbed开发板与ROS。实车测试表明控制器系统达到设计目的。     

考虑超级街区的城市路网边界控制策略研究

为缓解城市中心区交通拥堵状况,提出基于超级街区的路网多子区边界控制策略. 将城市区域路网划分为中心区、郊区及超级街区3个子区,结合宏观基本图(MFD)建立各子区交通流动态平衡方程;以中心区车辆出行完成率最高为目标,以边界收费费率和出、入口数量为控制变量,建立考虑车辆通道选择行为的路网多子区边界控制优化模型;并以实际路网数据为算例验证模型有效性.结果表明：边界控制策略下的中心区服务能力比无边界控制提高 7%;利用超级街区实现路网边界控制能够有效改善区域交通密度分布均衡性,提升路网服务效率;通过改变超级街区出、入口数量,实现边界控制兼备有效性和实践性.     

Multi-scale simulation for the forming of a heavy vessel head considering the evolution of defects and microstructure

The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production, due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.     

A new fractal model of elastic,elastoplastic and plastic normal contact stiffness for slow sliding interface considering dynamic friction and strain hardening

The deflection properties of elastic stage, elastoplastic stage and plastic stage of elastomer were analyzed. Taking account of the kinetic friction force in friction interface and strain hardening in slow sliding interface, the elastic, elastoplastic and plastic normal contact stiffness model for harsh surface was established, which revised the Majumdar-Bhushan fractal model and made it more perfect. In the combination of macro and micro perspective, the effects of coarse surface fractal variables, kinetic friction force in the friction interface, material characters of the friction couples on the contact status and contact property were discussed by the study of digital analysis. Results imply that the normal contact stiffness improves with the increasing real contact area and normal contact load, and reduces with the augment of kinetic friction coefficient. When the kinetic friction coefficient is smaller than 0.3, the normal contact stiffness comprises a linear decrease with the increment of kinetic friction coefficient. When the kinetic friction coefficient is bigger than 0.3, the normal contact stiffness has an exponential decrease with the increasing kinetic friction coefficient.     

考虑地域差异的柴油汽车排放清单建立方法研究

柴油汽车排放是目前城市大气污染的重要组成部分,如何结合区域差异建立柴油汽车排放清单是制定相关减排政策的基础工作.首先按照使用用途将柴油汽车划分为7种车型,选择国Ⅲ 、国Ⅳ、国Ⅴ共3种排放标准的车辆得到基础排放因子;具体分析不同区域的柴油汽车排放相关影响因素及修正权值,包含环境参数、车速分布、载重系数及劣化系数;结合修正参数建立柴油汽车综合排放因子计算公式及城市柴油汽车排放清单计算模型,以淄博市为例完成了城市柴油汽车排放清单的建立.研究结论表明,本文提出的柴油汽车排放清单建立方法,适用于结合不同城市的环境特征、车辆特征和道路特征定量评价柴油汽车污染排放状况,并为制定具体的柴油汽车污染物排放控制政策奠定基础.     

考虑腐蚀与疲劳损伤的船体总纵极限强度与可靠性分析

本文定量考虑了腐蚀与疲劳两类损伤对船体结构随时间变化的情况,并建立了船体总纵极限强度与时变可靠性的计算方法。对一条实船的分析说明,腐蚀和疲劳损伤虽然短时间内的破坏并不显著,但积累到一定程度,对船体结构的影响相当大。采用可靠性评估的方法,对船体总纵强度的安全水平可作出合理的评价。     

以泡沫金属为吸液芯的纳米流体热管传热性能试验研究

从热管的吸液芯对传热性能的影响出发,分别对以铜材泡沫金属和丝网为吸液芯的热管进行了传热性能试验研究,两种热管的工质都为质量浓度为1％的Al2 O3纳米流体。试验结果显示泡沫金属吸液芯热管在等温性、换热系数和传热极限等方面都要比丝网吸液芯热管更好,泡沫金属吸液芯热管的传热性能要优于丝网吸液芯热管。     

沥青混凝土与连续配筋混凝土复合式路面承载力分析

为了防止公路的早期破坏,为长寿命路面结构研究提供理论依据与技术支持,应用有限元方法对沥青混凝土与连续配筋混凝土复合式路面进行了温度场与疲劳应力分析。分析结果表明:小于4cm的沥青混凝土面层主要用于改善路面使用性能;大于4cm的沥青混凝土面层可以有效改善路面的温度场,每增加2cm,可满足15%～20%的超载要求。可见该复合式路面能够承受重载和一定程度的超载而不发生疲劳破坏。     

软土地基上硬壳层效应分析及其工程应用

分析了外加荷载(如路堤)作用下软土地基上硬壳层的工程效应包括壳体效应、封闭作用以及对沉降的滞后作用。针对硬壳层上述的工程效应,讨论了硬壳层在工程应用中应该注意的问题。     

土石混合料的工程分类研究

现行工程土石混合料多从颗粒粒径和各粒组含量进行分类,无法从分类上判断其强度指标。结合室内击实试验和剪切试验,以岩性、含石量和混合料颗粒组成的分形指标,将土石混合料按不同层次分为不同的类别,并由试验指出各类别土石混合料的强度差异,其综合分类法指标简单,易于应用,并可根据分类预测混合料的强度指标。