In the context of parallel collaborative lane-changing control for drivers and intelligent systems, issues such as human-machine conflict and driving discomfort arise due to frequent or substantial changes in the authority of the front wheel steering angle input. This paper proposes a lateral human-machine driving authority allocation strategy that combines pre-allocation with real-time allocation to achieve a reasonable allocation of vehicle control authority. Initially, to characterize the driving style of the driver, a single-point preview driver model is constructed, which includes decision functions for the tracking error and the lateral acceleration. Concurrently, a model predictive controller (MPC) is established as a co-driving control system, and a vehicle lane-changing trajectory is designed based on a quintic polynomial. Subsequently, a pre-allocation method for driving authority is designed, incorporating style coefficients, preview time, and road adhesion coefficients. Principles for real-time authority allocation are designed based on risk level and human-machine conflict, with adjustments introduced to prevent frequent changes in authority. Joint simulation results indicate that when human-machine intentions are consistent, this strategy significantly reduces the driver’s burden. When driving risk is high, control authority shifts toward the system, allowing timely intervention to ensure driving safety. When human-machine intentions are inconsistent, and driving risk is low but human-machine conflict is high, authority is transferred to the driver at a fixed value, allowing the vehicle to operate according to the driver’s intention, and the overall control effect is superior to fixed authority control strategies. Driver-in-the-loop platform tests have shown that this strategy can provide personalized lane-changing assistance for drivers of different styles, demonstrating superior performance compared to both fuzzy control and human-machine game control approaches.
The position deviation of the underwater manipulator generated by vortex-induced vibration (VIV) in the shear flow increases relative to that in the uniform flow. Thus, this study established an experimental platform to investigate the vibration characteristics of the underwater manipulator under shear flow. The vibration response along the manipulator was obtained and compared with that in the uniform flow. Results indicated that the velocity, test height, and flow field were the main factors affecting the VIV of the underwater manipulator. With the increase in the reduced velocity (Ur), the dimensionless amplitudes increased rapidly in the in-line (IL) direction with a maximum of 0.13D. The vibration responses in the cross-flow (CF) and IL directions were concentrated at positions 2, 3 and positions 1, 2, with peak values of 0.46 and 0.54 mm under Ur = 1.54, respectively. In addition, the vibration frequency increased with the reduction of velocity. The dimensionless dominant frequency in the CF and IL directions varied from 0.39-0.80 and 0.35-0.64, respectively. Moreover, the ratio of the CF and IL directions was close to 1 at a lower Ur. The standard deviation of displacement initially increased and then decreased as the height of the test location increased. The single peak value of the standard deviation showed that VIV presented a single mode. Compared with the uniform flow, the maximum and average values of VIV displacement increased by 104% and 110% under the shear flow, respectively.
When the global navigation satellite system(GNSS)signal is unavailable,the performance of GNSS/inertial navigation system(INS)integrated navigation system significantly degrades,which leads to the rapid divergence of INS errors of UAV swarms.At present,the neural network model is used to predict the position and speed instead of GNSS navigation information to correct the positioning error of the INS.However,this method suffers from high positioning errors and a sharp decline in prediction accuracy when the trajectory changes suddenly.Therefore,a position and velocity prediction method based on convolution neural networks(CNN)-bidirectional long short-term memory network(BiLSTM)joint residual compensation model is proposed to compensate for inertial navigation errors and improve position and velocity positioning accuracy.Firstly,aiming at the problem of high positioning error of GNSS/INS integrated navigation system after GNSS denial,a time series prediction network is formed by fusing CNN and BiLSTM to train and establish the relationship between inertial measurement unit(IMU)dynamics measurement and GNSS information,so as to realize position and speed prediction.Secondly,aiming at the problem that the prediction effect drops sharply when the trajectory changes abruptly,CNN-BiLSTM is used again to mine the relationship between the IMU dynamics measurement,prediction value and prediction residual,and to predict and compensate the prediction residual.Simulation results show that the proposed model outperforms traditional CNN-LSTM and LSTM network models in terms of prediction accuracy,effectiveness,and stability.
Aiming at the environmental pollution of the polishing solution in chemical mechanical polishing,a single-crystal SiC chemical mechanical polishing method based on metal electrochemical corrosion is proposed.The Si surface of single-crystal SiC corrosion performance and wear performance of electrochemically corroded were investigated by corrosion experiments and wear experiments.By comparing the corrosion performance of Al,Cu,and Fe metals on the Si face in a Na2SO4 electrolyte solution,it was found that only Al can generate a noticeable corrosion layer.The EDS and XPS analyses of the Si face confirmed that the corrosion is due to the formation of the SiO2 layer.Frictional wear experiments were conducted to investigate the influence of solution composition on the wear behavior of Si face.Increasing the concentration of the Na2SO4 electrolyte solution resulted in higher wear,with a maximum wear value of 7.19 µm2 obtained in 1.00 mol/L Na2SO4 electrolyte solution.In an acidic corrosive solution,the Si face exhibited the highest material removal,with a wear value of 11.97 µm2 achieved at pH=3.The material removal mechanism of single-crystal SiC via metal electrochemical corrosion involved the corrosive reaction involving Al at the cathode,which generated a corrosion current,and the subsequent oxidation of the SiC surface at the anode,thereby forming a SiO2 oxide layer leading to material removal.
为了在离散频域内求出由非零初始条件与外加荷载共同作用引起的结构的动力响应,基于傅里叶变换(FT)和有限差分公式,推导出了狄拉克 δ函数及其一阶导数的离散傅里叶变换(DFT),构建了一类新频域算法.利用这一算法,有效克服了传统的频域算法中由非零初始位移导致的动力响应数值发散.用三个数值算例来研究算法性能,分别是单自由度(SDOF)线性系统、4000个自由度的桁架结构、顶端具有集中质量的悬臂梁;它们均具有非零初始位移和初始速度.计算结果表明:改进后的频域算法与传统的数值算法算得的结果一致,且精度与效率更高,适用于求解各种类型的线性结构振动的动力响应.
为了制定提升高速公路网交通韧性的策略,提出一种基于组合赋权-云模型的路网韧性评价方法.首先,选取结构熵、边介数、聚类系数、路网密度4个路网拓扑结构指标和行程时间指数、路网流量非均匀指数2个交通运行状态指标,从路网拓扑结构与功能两方面对路网韧性进行综合评价.其次,对路网韧性等级进行划分,确定各评价指标在不同韧性等级的阈值,并基于逆向云发生器计算云参数特征值及确定度.随后,采用层次分析法和熵值法对指标进行组合赋权,通过加权平均得到不同韧性等级的隶属度,根据隶属度最大原则判定高速公路网韧性等级.最后,以某高速公路网为例进行实证研究,将所提出的组合赋权-云模型评价方法与综合模糊评价法进行对比.研究表明,二者的评价结果相近,但组合赋权-云模型评价方法克服了综合模糊评价法中随机性的缺陷,能更客观地反映路网的真实运行状态.
为实现IFC构件精确、高效分类,提出一种改进的多视图卷积神经网络(Multi-view Convolutional Neural Network,MVCNN)模型,该模型引入了自注意力模块和长短期记忆(Long Short-term Memory,LSTM)网络,针对MVCNN模型特征融合的局限性,设计了LSTM_ATT模块;通过对各视图数据特征关系的自适应调整,并结合注意力权重对输入的各视图数据进行融合,得到一个更具辨识性的3D形状描述符,从而提高模型对各相似IFC构件的分类检测性能.使用IFCNet数据集对建筑领域20个主要类别的IFC构件进行训练并在测试集上对改进MVCNN模型与MVCNN模型进行实验对比.实验结果表明,改进模型的分类准确率和F1值分别达到了88.27%、86.72%,相比改进前准确率提高了9.46%,对相似构件之间的分类识别效果明显.
为研究火灾下不锈钢构件的局部稳定性能及其破坏机理,介绍了8个奥氏体型焊接工字形截面短柱的轴心受压试验,其中包括6个高温试验和2个常温对照试验.分析试验构件的失稳模态和局部稳定承载力,利用有限元模型对影响构件局部稳定性能的重要因素做了参数分析.结合试验与数值分析结果,对现有欧洲规范设计方法进行了评估.结果表明:随着温度升高,构件的刚度下降,屈曲变形增大,局部稳定承载力降低幅度增大;初始缺陷对构件承载力影响较小,截面宽厚比是影响局部承载力的关键因素;现有欧洲规范设计方法预测结果较为准确.
通过大涡模拟对屋顶槽式聚光器组的风压分布规律展开研究,并将数值模拟结果和风洞试验结果进行对比,验证了大涡模拟结果的准确性.对9个平屋顶聚光器组成的镜群在0°仰角工况下的风压分布进行模拟,得到平屋顶聚光器组在不同风向角下的最不利位置及其风压系数的分布规律.结果表明,正风向下,屋顶靠近来流风上游的一排聚光镜承受了绝大部分的风荷载,中间及后排的聚光镜风压系数为前排的8.75%;斜风向下,后排聚光镜的最大风压系数为前排聚光镜的17.6%;屋顶的角落位置为聚光器组的最不利位置,所得结论可为平屋顶槽式聚光器的群组结构抗风设计提供理论依据.
通过节段模型风洞试验,研究雷诺数Re=307～906时圆杆正方形塔架的阻力系数,分析密实比、湍流度及风速等因素的影响.在试验研究的基础上,对比3种雷诺平均模型在圆杆正方形塔架气动力CFD数值模拟中的适用性,分析Re=300～2.5×104时阻力系数变化规律及影响因素.试验结果表明:圆杆正方形塔架的平均阻力系数在45°风向角时最大,0°和90°最小,并随密实比和风速的增大而减小,随湍流度的增大而增大;脉动阻力系数受密实比和风向角的影响不大,但随风速和湍流度的增大而增大.CFD数值结果显示:SST k-ω湍流模型在Re≤2.5×104时更适用于计算圆杆正方形塔架的平均阻力系数;随雷诺数的增大,塔架平均阻力系数在Re=300～585时急剧减小,Re=585～1 090时减小趋势少许放缓,Re=1 090～2.5×104时基本保持不变;完全处于上游杆件尾流区的下游杆件阻力系数相比于上游杆件减小50%左右.
提出一种在试件损伤过程中,以数字图像方法所得应变场为基础,采用机器视觉识别快速获得对应损伤状态下试件表面裂缝分布的裂缝自动识别检测(Automated Crack De-tection and Measurement,ACDM)方法.采用三点弯曲试验,以夹式位移计测量裂缝口张开位移(Crack Mouth Opening Displacement,CMOD)作为参考用真实值,对ACDM的精度进行分析.结果显示,CMOD小于0.05 mm时,ACDM识别的误差小于0.01 mm,ACDM方法可用于分析微裂缝尺度的混凝土损伤情况.通过3组不同强度混凝土立方体试件的压缩试验,采用ACDM方法所得裂缝面积直接表征损伤指标来反映试件的损伤演化情况.结果表明,在宏观裂缝出现之前,在不同损伤阶段下由ACDM方法所得损伤指标,对应数值变化均大于10-3,与目前表征损伤应变场的不均匀性变异系数(Cv)相比更为灵敏和准确.
针对预制钢管-混凝土组合柱的连接可靠性问题,提出了预应力增强的芯管连接方案,其采用锚入柱预埋钢管内部的Q420高强芯管连接,并通过结构通高设置的后张无黏结预应力筋进行压接增强.为探讨该新型连接组合结构柱的抗震性能,对1个现浇对比试件和3个采用不同规格芯管连接的装配式试件进行低周反复水平荷载试验,通过对比各试件的破坏形态、滞回曲线与骨架曲线、承载力、刚度、位移延性等,综合评价其抗震性能.基于试验结果,开展了芯管直径及壁厚、芯管长度、连接盖板厚度、预应力筋张拉控制应力等有限元参数分析.试验及参数分析结果表明,装配式试件总体上可实现"等同现浇"的抗震性能,但应考虑刚度提高导致结构地震力效应增大的不利影响;随着芯管截面规格的增大,其承载力、刚度及延性性能逐渐提高,采用D152 mm×16 mm芯管的装配式试件为推荐方案;芯管连接件截面积相当时,建议选用惯性矩更大的截面,黏结长度可按3倍直径设计,连接盖板厚度可按构造确定;对于本次设计试件,预应力筋张拉控制应力建议在0.3～0.6倍预应力筋屈服强度标准值范围内确定.
为研究两边连接内加劲双钢板剪力墙的抗剪承载力,采用ABAQUS程序进行36个不同宽高比、不同高厚比的两边连接内加劲双钢板剪力墙的有限元分析.分析结果表明,采用厚板或宽高比较大的钢板均可以使钢材达到较高的平均应力水平;峰值平均剪应力与屈服平均剪应力的比值随高厚比或宽高比变化的规律不明显,强屈比随高厚比变化介于1.17～1.21之间,随宽高比的变化介于1.16～1.21之间,平均值均为1.19;给出了宽高比为0.33～2.00、高厚比为200～750的两边连接内加劲双钢板剪力墙屈服平均剪应力计算公式;采用结构力学位移计算原理推导的理论计算公式可准确计算内加劲双钢板剪力墙的初始刚度和初始等效剪切模量.建立了两边连接内加劲双钢板剪力墙的等效交叉杆模型,验证了等效交叉杆模型可以精准地模拟不同宽高比、不同高厚比两边连接内加劲双钢板剪力墙的屈服平均剪应力和初始刚度,表明可以采用等效交叉杆模型简化两边连接内加劲双钢板剪力墙的设计与分析.
基于无人机摄影测量及随机振动测试的方法,探索在不封闭交通条件下进行桥梁状态评估的方法.以长沙市某大桥为例,通过采用结构识别理论与无人机倾斜摄影技术分别对桥梁线型、桥梁病害、动力特性进行研究.利用无人机三维倾斜摄影技术重建目标桥梁三维实景模型并通过点云模型提取桥梁线型,将无人机测量线型与水准测量线型以及设计线型进行对比,研究发现线型差值的平均值为0.034 m,平均相对挠度值为L/12705(L为桥梁跨度),标准差为0.035 m,两者结果较为接近,验证了无人机测量桥梁线型的可靠性,也验证了运营桥梁期间外观尺寸无显著改变.利用小型无人机技术对目标桥梁辅助进行外观质量调查,调查桥墩病害和支座损伤特征,结果表明桥梁无结构性损伤.通过对结构进行环境振动测试,以行车、风等荷载作为激励,利用复模态指示函数(Complex Modal Indicator Function,CMIF)法捕捉结构模态参数(频率、振型、阻尼比),对比10 年前历史基线模态数据并综合考虑环境温度影响,判断该桥结构刚度无明显下降.研究表明采用"无人机三维建模线型测量+无人机病害调查+随机振动测试"的桥梁健康状态的综合评估技术具有可行性、经济性及实用性.
为研究不同参数的螺旋线对斜拉索涡激振动特性和气动力的影响规律,进行了针对表面无螺旋线斜拉索和缠绕不同参数螺旋线斜拉索的节段模型风洞试验,螺旋线参数包括根数、直径和缠绕间距.结果表明:斜拉索表面缠绕1根螺旋线的涡激振动振幅远大于2根或3根螺旋线;在亚临界雷诺数区,缠绕螺旋线斜拉索的平均气动阻力系数均小于无螺旋线斜拉索,最多可减小10.9%;缠绕2根螺旋线的斜拉索平均阻力系数整体比3根螺旋线小.斜拉索表面缠绕间距s=8D(D为斜拉索直径)的2根螺旋线时,缠绕直径d<15 mm螺旋线的斜拉索涡激振动现象明显;d≥15 mm的螺旋线可显著降低斜拉索涡激振动响应幅值,其脉动升力系数相较于无螺旋线斜拉索有明显降低,证明缠绕大直径螺旋线对涡激振动响应控制的有效性.螺旋线的缠绕间距对斜拉索涡激振动的影响与螺旋线直径有关,当螺旋线直径较小时,缠绕间距对涡激振动的影响并不明显;当螺旋线直径较大时,间距的大小直接影响涡激振动的抑制效果.
为研究输电塔在土结相互作用(Soil Structure Interactions,SSI)和塔-线耦合作用影响下的抗震可靠度,提出了考虑SSI效应的输电塔-线耦合系统抗震可靠度分析方法.建立考虑SSI效应的输电塔-线耦合系统简化力学模型,推导其在随机地震作用下的运动方程.基于随机函数-谱表示方法模拟随机地震动加速度时程,对耦合系统进行随机地震动力响应分析.以基于GF-偏差点集的样本分数矩最大熵法估计随机地震响应极值分布,并求解耦合系统抗震可靠度.选取工程中某特高压输电塔-线体系作为研究对象,对本文方法的有效性进行验证.结果表明,当塔底地基土为软弱土时,考虑SSI效应后,塔顶位移响应极值增大约46.59%,加速度响应极值增大约17.43%,结构失效概率增加约70.32%.考虑塔-线耦合作用后,塔顶位移响应极值减小约0.51%,加速度响应极值增大约1.74%,结构失效概率减小约15.71%.对于考虑SSI效应的输电塔-线耦合系统,塔底地基土越软,塔顶位移与加速度响应极值越大.与蒙特卡洛法相比,本文方法求解的结构失效概率最大误差仅为9.97%,具有较高的精度和计算效率.
根据锌铝合金镀层的电化学腐蚀原理,结合锌铝合金镀层微观组织试验、镀层均匀性试验、中性盐雾腐蚀试验数据,建立适用于锌铝合金镀层的二维腐蚀元胞自动机模型,模拟锌铝合金镀层的腐蚀演化过程,分析镀层金属氧化反应、水化反应、水化物溶解反应和镀层不均匀性对腐蚀过程的影响规律.研究结果表明,二维腐蚀元胞自动机模型能够准确模拟锌铝合金镀层的腐蚀演化过程;在镀层腐蚀过程中,金属的氧化反应起主导作用,金属的水化反应和金属水化物的溶解反应是次要因素;同一时刻,氧化概率大小与单位面积金属腐蚀量呈非线性正比关系,溶解概率大小与单位面积金属腐蚀量呈非线性正比关系,水化概率大小与单位面积金属腐蚀量呈反比关系;镀层金属含量的不均匀分布对镀层腐蚀演化过程影响较小,镀层厚度的不均匀性会导致局部区域铁基体过早发生腐蚀,引起蚀坑的出现.
采用工程水泥基复合材料(Engineered Cementitious Composite,ECC)沿水平灰缝对砖砌墙体进行嵌缝加固,几乎不改变其外观,符合文物建筑修旧如旧原则.为研究ECC水平嵌缝加固砖砌体的剪切性能,以聚乙烯纤维(PE)、聚乙烯醇纤维(PVA)和混杂纤维(PVA与PE)等不同纤维类型、PE纤维掺量、嵌缝间距和单双面加固为变量,开展砖砌体在剪压作用下的对角剪切试验.对比分析ECC加固砖砌体墙的破坏模式、荷载-位移曲线、剪切强度和延性,探究ECC与砖砌体的协同工作性能.试验结果表明:ECC水平嵌缝加固减缓了砖砌体内部裂缝的开展,提升了试件的抗剪承载力和破坏时的整体性,加固试件的抗剪强度最大提升了44.5%,加固面的最大抗剪刚度约为未加固面的5倍.
对是否设置加强环板、不同节点板宽度和钢管轴压力的6组共12个Q460钢管管板连接节点进行受弯承载力试验研究.结果表明:无加强环板试件在节点板两端由于应力集中,承载力较低,有加强环板试件的节点板两端应力分布均匀,试件承载力显著提高.当节点板宽度与钢管直径之比由2.5增大到3.0时,无加强环板、1/4加强环板、1/2加强环板试件的承载力分别提高6.10%～16.07%、13.36%～20.68%、9.61%～12.34%.与无加强环板试件相比,1/4加强环板试件的承载力提高 102.86%～130.73%,1/2 加强环板试件的承载力提高 129.88%～166.33%.当钢管轴压比由0.10增大到0.23时,无加强环板、1/4加强环板、1/2加强环板试件的承载力分别降低10.05%～17.77%、10.79%～16.20%、4.74%～7.05%.现有规范对于无加强环板节点的承载力计算偏于保守.考虑加强环板和钢管轴力对节点受弯承载力的影响,提出了Q460钢管管板连接节点的受弯承载力计算公式,与试验结果吻合较好.
为研究附加攻角效应对分离式三箱梁颤振性能的影响,结合节段模型风洞试验和理论计算方法获得初始风攻角下的附加攻角,并通过计算流体动力学(Computational Fluid Dy-namics,CFD)数值模拟方法求解初始风攻角下的颤振临界风速.结果表明,分离式三箱梁的初始风攻角及箱梁之间的横梁对附加攻角有较大影响,节段模型在0°～+7°风攻角下存在十分显著的附加攻角效应,且表现为扭转振幅快速增大的硬颤振.节段模型自由振动风洞试验难以直接获得分离式三箱梁在小风攻角下的准确颤振临界风速.对于主跨3 300 m的悬索桥,0°初始风攻角下在颤振失稳前的静风附加攻角达到+7°以上,颤振临界风速大大降低,气弹稳定性得不到充分发挥.因此,对于采用分离式三箱梁断面的超大跨径桥梁,在抗风设计中应对其附加攻角效应予以重视.
