预加速在汽车冲模中的应用与行程图设计

通过预加速在斜楔滑块中的应用分析,提出了预加速设计的必要性,从结构特点,应用情况,参数设计,预加速行程图设计等方面进行详细阐述,让模具设计者对预加速在滑块中的应用有更深的理解与掌握,供设计者与同行参考。

基于最优预瞄加速度决策的汽车自适应巡航控制系统

从驾驶员操作汽车的行为特性建模的角度出发,将驾驶员建模理论———稳态预瞄动态校正假说应用于汽车自适应巡航控制系统的理论研究中,构建了基于驾驶员最优预瞄加速度模型的车辆ACC系统结构。并在此基础上建立了相应的ACC系统控制算法。理论分析与仿真计算结果表明:基于驾驶员操纵行为特性的分析,应用驾驶员操纵行为建模理论来研究汽车ACC系统的理论过程为车辆ACC系统的开发提供了一个可行的研究途径。

最优预瞄加速度驾驶员模型参数试验辨识方法研究

研究通过试验辨识获得最优预瞄加速度驾驶员模型物理参数的方法。采用时域辨识方法确定模型传递函数,采用非线性最小二乘法确定传递函数中所包含的物理参数,利用已知目标函数优化预瞄时间和反应时间,针对仿真数据进行了辨识分析。结果表明,该方法对驾驶员模型物理参数的辨识具有良好的效果。

基于MCU的Flash预取加速控制器设计与实现

为了解决低成本低功耗微处理器(Micro Control Unit,MCU)中嵌入式Flash读取速度的问题,基于预取和缓存原理,采用位宽扩展技术和改进预取技术相结合的方式,设计了具有预取加速功能的Flash控制器。实现Flash特定接口协议与高级高性能总线(Advanced High-performance Bus,AHB)协议的转换,提高处理器取值效率,提升系统性能。设计了完善的读写保护机制,以保护用户程序。同时搭建片上系统(System on Chip,So C)仿真实验平台验证设计的正确性,实验结果表明,本设计最多提高了16.3%的取指效率,并在实际样片中得以验证。

VVER型核电机组反应堆控制保护系统加速预保护信号执行回路逻辑研究与设计优化

针对反应堆控制保护系统加速预保护信号执行回路逻辑设计不合理,存在单一设备故障导致机组降功率问题,开展加速预保护信号执行回路逻辑优化改造,避免单一设备故障造成的重大影响及后果,提高系统的可靠性。

ISO 362-1:2007中M1类车加速方法研究

标准ISO 362-1:2007提出了新的测试限值和方法,但其中试验的加速入线方法尚未明确,给测试机构带来了较高的测试难度。针对此问题,基于理论分析,通过试验建立Simulink数学模型对M1型汽车进行研究,考虑距离和起始速度的耦合,对车辆的预加速距离和加速起始车速进行了两种不同加速方法下的预测。经试验验证,符合率为80%,平均准确度为0.612 km/h,最低误差可达到0.2%,具有较高的准确度。该模型对于标准的执行,降低了试验的准备难度和复杂程度,一定程度填补了标准中对于加速方法的空缺。

不同预燃室结构对甲烷湍流射流点火燃烧的影响

基于光学定容燃烧弹试验平台,通过高速纹影摄像系统在相同甲烷燃料初始温度、压力及混合气浓度下,定量分析了不同结构预燃室湍流射流点火(turbulent jet ignition,TJI)的燃烧特性,包括火焰传播速度、火焰面积、火焰形态及燃烧压力等参数。研究结果表明,预燃室孔径越小,相同时间内火焰传播得越远,火焰传播速度和火焰面积增长速度越快,燃烧压力峰值越高。随着预燃室孔径减小,着火机理会由射流中带有火焰的火焰点火转变为火焰过孔时熄灭的喷射点火。喷射点火着火时刻延迟,初始火焰速度减慢,但燃烧压力峰值受影响不大。多级加速预燃室压力升高率与压力峰值与单孔预燃室相比变化不大。虽然火焰出口时速度较慢,但是火焰出口时刻提前且速度衰减较弱,因此多级加速预燃室火焰速度在短时间内超过单孔预燃室,并且压力和火焰面积也更早达到最大值。

ISO 362—1:2007在M1类车辆试验中的应用

阐述了M1类车辆依据ISO362-1:2007《道路车辆加速行驶噪声测量工程法》的试验过程及数据处理方法,并结合实例进行验证。阐述了目标加速度值和参考加速度值的内涵。针对测试过程中存在的挡位初步选择、入线速度及预加速距离估算等技术难点,提出了一种实用方法:在噪声测试前采用速度、加速度、位移数据采集设备及触发装置对样车进行加速试验,通过对车辆加速特性进行分析,即可快速解决上述技术问题。

试模液压机发展现状简介

随着全球经济一体化及产业分工的日益加深,我国作为典型的新兴国家代表,汽车产业发展迅速。汽车行业的快速发展离不开压机行业的助力,试模压力机是必不可少的关键设备。试模液压机除了具备普通液压机的功能与配置外,还有满足试模工艺要求的辅助功能部件及控制。经过专业工作者的不懈努力,开发了许多新技术,使试模液压机的功能更强大、更完善,例如:液压垫的预加速功能,多曲线液压机,以及配套齐全的试模中心。试模液压机的发展影响着汽车制造业的前进步伐。

大型汽车冲压生产线伺服拉伸垫的发展现状

介绍了伺服拉伸垫的基本功能。对几家高端汽车钣金冲压生产线的伺服拉伸垫的工作原理、结构、技术特点进行分析、比较。希望给伺服拉伸垫的选型和开发提供参考。

液气式数控拉伸垫的若干计算

汽车工业中大型覆盖件冲压生产对冲压设备提出了越来越高的要求,促进了大型压力机技术迅速发展。数控拉伸垫是大型压力机的关键部件。在压力机拉延工件时,依据板料成形工艺要求,通过拉伸垫实时控制压边力。本文在研究产生压边力的方案基础上,对应液气式数控拉伸垫的控制曲线,对其工作原理进行了分析,着重分析了预加速运动和压边力控制过程。对液压系统进行了静态计算以便主要元件选型,并对辅助动力系统和系统产生的热量进行了计算。

关于投掷的两个力学原理及其运用

田径运动的投掷有铅球、铁饼、标枪、手榴弹、链球等。这些项目虽然所用的器械和方法各不相同,但投掷技术都要符合力学原理,才能投掷得更远。因为,投掷的成绩决定于投掷物的出手速度、角度、空气阻力三个要素。那么,它的出手速度是怎样形成的呢?它与人体有何运动关系?这是我们着重要研究的两个问题,也是改进教学、提高训练水平和投掷成绩的关键.

The bound weighted average method(BWAM)for predicting S-wave velocity

The shear-wave velocity is a very important parameter in oil and gas seismic exploration, and vital in prestack elastic-parameters inversion and seismic attribute analysis. However, sheafing-velocity logging is seldom carried out because it is expensive. This paper presents a simple method for predicting S-wave velocity which covers the basic factors that influence seismic wave propagation velocity in rocks. The elastic modulus of a rock is expressed here as a weighted arithmetic average between Voigt and Reuss bounds, where the weighting factor, w, is a measurement of the geometric details of the pore space and mineral grains. The S-wave velocity can be estimated from w, which is derived from the P-wave modulus. The method is applied to process well-logging data for a carbonate reservoir in Sichuan Basin, and shows the predicted S-wave velocities agree well with the measured S-wave velocities.

Prediction of preheating conditions for inclined laser assisted machining

For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.

Direct reduction of carburized pre-reduced pellets by microwave heating

A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 ℃ in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperatttre carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 ℃ in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet, respectively.

Simulation of the Microphysical Processes and Effect of Latent Heat on a Heavy Rainfall Event in Beijing

An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.

Material Removal Rate Prediction of Electrical Discharge Machining Process Using Artificial Neural Network

This article presents an Artificial Neural Network （ANN） architecture to model the Electrical Discharge Machining （EDM） process. It is aimed to develop the ANN model using an input-output pattern of raw data collected from an experimental of EDM process, whereas several research objectives have been outlined such as experimenting machining material for selected gap current, identifying machining parameters for ANN variables and selecting appropriate size of data selection. The experimental data （input variables） of copper-electrode and steel-workpiece is based on a selected gap current where pulse on time, pulse off time and sparking frequency have been chosen at optimum value of Material Removal Rate （MRR）. In this paper, the result has significantly demonstrated that the ANN model is capable of predicting the MRR with low percentage prediction error when compared with the experimental result.

通过噪声新标准试验因素结果差异分析及应对办法

GB 1495《汽车加速行驶车外噪声限值及测量方法(中国第三、四阶段)》(报批稿)相对于GB 1495—2002现行标准,试验工况更为复杂,限值要求也相对更为严格。通过对不同车型开展测试,从预加速距离和不同驾驶模式两种情况导致的试验结果差异进行举例介绍并对其产生原因进行分析,同时提出了应对办法及建议。

基于任务坐标系的液压机四角调平控制

针对液压机滑块的四角调平电液系统,提出了一种基于空间任务坐标系的控制方法。分析滑块与调平缸的运动关系与空间位置关系,从而建立坐标转换矩阵,将液压机滑块四角的直线位移坐标转换为滑块中心位移与倾角组成的任务坐标,在任务坐标空间内设计了基于调平力偏置非线性前馈补偿的滑块跟踪运动PID控制器,并且直接针对滑块的倾角设计了调平PID控制器,针对不同控制目标的控制参数是独立调节、互不影响的。设计了基于调平力偏置的预加速过程,以缓解滑块与调平缸接触时的冲击。最后,在25000 kN玻璃钢液压机上对所提控制方法的有效性进行实验验证。实验中,调平缸分别定位于平面矩形的四角,矩形尺寸为3550 mm×2900 mm。实验结果表明:使用基于任务坐标系的四角调平控制方法后,液压机滑块绕坐标轴x、y的旋转倾角分别被控制在0.0032°和0.0045°以内,各调平缸的位移偏差不超过0.45 mm。