Comparison of two suspension control strategies for multi-axle heavy truck

Two simple and effective control strategies for a multi-axle heavy truck, modified skyhook damping (MSD) control and proportional-integration-derivative (PID) control, were implemented into functional virtual prototype (FVP) model and compared in terms of road friendliness and ride comfort. A four-axle heavy truck-road coupling system model was established using FVP technology and validated through a ride comfort test. Then appropriate passive air suspensions were chosen to replace the rear tandem suspensions of the original truck model for preliminary optimization. The mechanical properties and time lag of dampers were taken into account in simulations of MSD and PID semi-active dampers implemented using MATLAB/Simulink. Through co-simulations with Adams and MATLAB, the effects of semi-active MSD and PID control were analyzed and compared, and control parameters which afforded the best comprehensive performance for each control strategy were chosen. Simulation results indicate that compared with the passive air suspension truck, semi-active MSD control improves both ride comfort and road-friendliness markedly, with optimization ratios of RMS vertical acceleration and RMS tyre force ranging from 10.1% to 44.8%. However, semi-active PID control only reduces vertical vibration of the driver’s seat by 11.1%, 11.1% and 10.9% on A, B and C level roads respectively. Both strategies are robust to the variation of road level.     

Selection model of trip time for rural population

Referring to the 1 248 survey data of rural population in 14 provinces of China, the influencing factors of trip time choice were analyzed. Based on the basic theory of disaggregate model and its modelling method, nine grades were selected as the alternatives of trip time, the variables affecting time choice and the method getting their values were determined, and a multinomial logit (MNL) model was developed. Another 1 200 trip data of rural population were selected to testify the model’s validity. The result shows that the maximum absolute error of each period between calculated value and statistic is 3.6%, so MNL model has high calculation accuracy.     

改性HZSM-5催化合成异丙醇胺

利用等体积浸渍法和离子交换法对硅铝摩尔比38的HZSM-5进行硝酸钾、硝酸钠和磷酸氢二铵离子改性,并采用XRD、BET、NH₃-TPD等表征方法对催化剂结构和酸性进行表征。在自制微型固定床反应器上对离子改性前后的HZSM-5分子筛上进行环氧丙烷的开环氨解反应活性评价,考察离子改性对催化剂晶体结构、酸性、孔结构以及催化剂性能的影响。结果表明：离子改性不会破坏分子筛的晶体结构,改性前后均具有较高的比表面积、孔容积、孔径,不同离子改性对分子筛的酸性影响较大,强酸密度均有所降低,有效提高了一异丙醇胺的选择性,延长催化剂使用寿命。相比未处理的HZSM-5分子筛,K⁺离子改性后的分子筛强酸性位点完全消失,相同反应条件下一异丙醇胺选择性由42.29%提升至73.72%,连续运转120 h转化率仍保持在90%以上,表现出良好的催化性能。     

半主动磁流变阻尼器悬架的一种ANFIS-PID控制策略

针对磁流变阻尼器现象模型的逆模型建立问题和PID参数整定问题,提出了基于自适应神经模糊推理系统(ANFIS)建立的逆向模型和ANFIS-PID控制器。对1/4车辆半主动磁流变阻尼器悬架和控制系统进行联合仿真,仿真结果表明,与PID控制相比,ANFIS-PID控制有效的改善了簧载质量加速度、悬架动行程和轮胎动变形,表明提出的控制策略是有效的,为半主动磁流变阻尼器悬架的研究提供了一种可行途径。     

综合客运多枢纽协调布局优化模型

考虑综合交通枢纽场站协调优化布局,在传统客运枢纽规划模型中增加用户对运输模式的选择与枢纽中转能力两个约束条件,提出基于容量限制与运输模式选择的综合客运多枢纽布局非线性整数规划模型,设计了改进的遗传算法对其进行求解。应用LINGO软件对布局优化模型进行有效性检验,对8节点Solomon标准测试数据进行计算,得出LINGO平均运算时间为5 102s,最优成本为1 899 782元;遗传算法MATLAB编程平均运算时间为59s,最优成本为1 948 796元。对50节点数据进行运算,平均运算时间为569s,最优成本为8 497 602元;使用25节点规模的AP数据集合,取枢纽数量为3时得出的最优成本为154 932元,应用传统枢纽规划模型进行求解,平均运算时间为607s,最优成本为155 098元,比经典算法降低了166元。可见,与传统枢纽规划模型相比,该模型与算法最优成本更少,说明改进的枢纽布局优化模型有效。     

中小企业对数控机床的日常管理

介绍了中小企业对数控机床的日常管理内容。通过中小企业的规范管理,督导管理者认真履行日常管理职责,保持数控机床处于良好的工作状态,使其发挥出最大效能。     

照度与视觉敏感度对驾驶辨识行为的影响研究

为分析环境照度对驾驶人辨识目标物的影响,以视觉对比敏感度和机动车行车制动过程为理论基础,通过设计照度和目标物色彩变化实验,获取驾驶人在静态环境下辨识目标物时间相关数据,对颜色、照度和辨识时间数据进行拟合与分析,得出了照度变化下驾驶人辨识不同组合色彩目标物的时间差异性规律,并构建了跟车安全距离模型,在模型中引入上述辨识时间参数,建立了驾驶人辨识时间模型,综合考虑各照度条件下的视力水平变化和辨识时间长短,提出了基于交通安全最优的交通标志最佳配色方法。