鼓式制动器结构振动噪声研究

本文阐述了制动器制动噪声发生的一般机理,给出了鼓式制动器低频(发啃)和高频(尖叫)振动噪声的实际结构闭环耦合模型,较为完善地考虑了各种结构系数的影响。模型的仿真分析结果和试验结果取得良好一致。提高了对制动噪声的定量分析,证明了通过改变结构的特性参数匹配可有效地抑制制动噪声的发生。     

The Methodology Research on the Test and Evaluation of Static Stiffness of Elastic Pads in Elastic Separated FastenerEI北大核心

Research purposes: In order to explore the reasonable test and evaluation methods of the static stiffness of the elastic pads in elastic separated fastener, the influences of various factors on the static stiffness of the elastic pads were tested and analyzed by single factor test, a reasonable static stiffness test plan for the elastic pads was proposed. Besides, the evaluation suggestions for static stiffness of rail pad and baseplate pad were analyzed in terms of the installation state of the elastic separated fastener. Research conclusions:(1) The test of the static stiffness of elastic pad should include two stages: preloading stage and formal loading stage. Firstly, the elastic pad shall be preloaded with no less than 2 times at a loading rate of 3-5 kN/s, and the preloaded maximum load shall be at least 10 kN higher than the static stiffness test load range of the elastic pad. Then, formal loading is supposed to be carried out at least 3 times with a loading rate of 1~2 kN/s, and at both ends of the load range the load should be maintained for 90 s, which could be shortened to 60 s in special case when the load is less than 100 kN. Finally, the static stiffness of the elastic pad is calculated by the average value of the three test results. (2) The evaluation methods of static stiffness of rail pad and baseplate pad are dissimilar. The static stiffness of the rail pad could be evaluated by the secant stiffness in the range of 20~70 kN, while the evaluation of static stiffness of baseplate pad should be processed in terms of the reasonable static stiffness test load range of baseplate pad determined by the installation torque of anchored bolt. (3) This research results can be applied in the test and evaluation of static stiffness of rail pad and baseplate pad in elastic separated fastener. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

Test Analysis of the Vibration Response of Trough Girder Bridge in the Small Radius CurveEI北大核心

Research purposes: The bridge in circinate line of Hefei Railway Hub was built in the curve with radius of 300 m. In order to reduce structural height of the bridge across the Huainan railway, the single-line simple trough girder bridge with 32 m span was applied. The lateral vibration of the vehicle and bridge is intensified under the action of centrifugal force, and the torsion effect is obvious when the train running on the bridge in the small radius curve. On the other hand, the torsional rigidity of the trough girder with open section is lower than that of the closed box girder. Moreover, the wheel lateral force and the derailment coefficient is increased, and the reduction rate of wheel load is also increased owing to centrifugal force caused by unbalanced superelevation. In order to ensure the safe and smooth operation of the train and reveal the dynamic performance of the trough girder bridge in the small radius curve, the vibration response of the single-line trough girder bridge is tested and analyzed. Research conclusions:(1) The measured vertical and horizontal fundamental frequencies of the trough girder bridge are obviously larger than the vertical self-vibration frequency limit given by the relevant specification and the normal value of the measured transverse minimum natural vibration frequency. The lateral stiffness of the bridge is mainly controlled by its foundation stiffness. (2) The stiffness of the bridge can meet the requirements of C62 freight train safe running on the trough girder bridge in the curve with radius of 300 m at a speed of not more than 40 km/h. (3) The transverse vibration response of the bridge consists of the transverse static response of the structure caused by the centrifugal force and the lateral dynamic response caused by the coupling vibration of the vehicle-bridge system. (4) The research results can be referenced in the design of the railway bridge in the curve and coupled vibration analysis of trains and bridge in the small radius curve. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.     

北京轨道交通一体化 开发案例分析

结合目前北京轨道交通上盖一体化、沿线地下空间一体化、站域综合体一体化开发、沿线土地一体化开发的典型案例,对其相关政策、体制、投资、开发模式等问题进行深入探讨,总结出一套“统一主体,统一规划,同步设计,同步实施”的开发模式,提出需要大力进行政策、体制、立法的创新,进一步助推北京轨道交通一体化事业的健康持续发展.     

玄武岩纤维/铝合金层合板低速冲击性能及应用研究

制备一种玄武岩纤维/铝合金层合板复合结构,通过试验和仿真,探讨该复合结构的拉伸、压缩、剪切、弯曲和抗冲击特性。采用连续壳单元模拟纤维层,建立低速冲击仿真模型,从能量吸收、接触力和层合板损伤程度3个方面,研究铺层结构和冲击载荷角度对纤维金属层合板抗冲击性能的影响。最后,将纤维金属层合板应用于发动机罩外板,进行发动机罩静态刚度和行人头部碰撞仿真分析。结果表明,与原发动机罩相比,纤维金属层合板发动机罩的弯曲刚度和扭转刚度均有不同程度提高,行人头部保护性能得到改善。     

驾驶员PO预瞄模型参数的时域辨识

本文通过斜坡响应不变法实现离荼到连续传递函数间的转换，运用Ｍａｒｑｕａｒｄｔ阻尼最小二乘法辨识驾驶员ＰＯ预瞄模型的物理参数。辨识结果中，当信噪比为２０ｄＢ、４ｄＢ时，最大偏差分别为１．６％及１０％，从而表明斜坡响应不变法具有很高的辨识精度，且因采用阻尼最小二乘法致使物理参数识精度进一步提高。     

点火与燃油喷射相结合的电控汽油喷射系统

介绍了一种点火与燃油喷射相结合的电控汽油喷射系统及其点火子系统、喷油子系统、电控单元的结构及工作原理，并阐述了该系统的主要优点。论述了在冷起动工况、暖车工况、加速工况、全负荷工况以及怠速工况时，系统的点火控制功能和混合气匹配情况。     

Optimal design of three-planetary-gear power-split hybrid powertrains

Many of today’s power-split hybrid electric vehicles (HEVs) utilize planetary gears (PGs) to connect the powertrain elements together. Recent power-split HEVs tend to use two PGs and some of them have multiple modes to achieve better fuel economy and driving performance. Looking to the future, hybrid powertrain technologies must be enhanced to design hybrid light trucks. For light trucks, the need for multi-mode and more PGs is stronger, to achieve the required performance. To systematically explore all the possible designs of multi-mode HEVs with three PGs, an efficient searching and optimization methodology is proposed. All possible clutch topology and modes for one existing configuration that uses three PGs were exhaustively searched. The launching performance is first used to screen out designs that fail to satisfy the required launching performance. A near-optimal and computationally efficient energy management strategy was then employed to identify designs that achieve good fuel economy. The proposed design process successfully identify 8 designs that achieve better launching performance and better fuel economy, while using fewer number of clutches than the benchmark and a patented design.     

Novel stability control strategy for distributed drive electric vehicle based on driver operation intention

In this paper, a novel direct yaw control method based on driver operation intention for stability control of a distributed drive electric vehicle is proposed. It was discovered that the vehicle loses its stability easily under an emergency steering alignment (EA) problem. An emergent control algorithm is proposed to improve vehicle stability under such a condition. A driver operation intention recognition module is developed to identify the driving conditions. When the vehicle enters into an EA condition, the module can quickly identify it and transfer the control method from normal direct yaw control to emergency control. Two control algorithms are designed. The emergency control algorithm is applied to an EA condition while the adaptive control algorithm is applied to other conditions except the EA condition. Both simulation results and real vehicle results show that: The driver module can accurately identify driving conditions based on driver operation intention. When the vehicle enters into EA condition, the emergent control algorithm can intervene quickly, and it has proven to outperform normal direct yaw control for better stabilization of vehicles.     

Combustion and emission characteristics of a lean burn natural gas engine

Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings, spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio, spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results in high cyclic variations.