非确定因素下汽车半主动悬架的智能控制

以含磁流变阻尼器的1/4 车辆非线性半主动悬架模型为研究对象,在充分考虑该非线性系统未建模动态的基础上提出了具体的神经网络与滑模变结构控制相结合的智能控制策略,有效抑制了悬架系统的振动,使车辆行驶的平顺性与舒适性得以提高.应用神经网络的在线学习能力对非线性动力学模型的不确定部分及外界未知扰动进行了神经网络估计,确定了未知函数的上确界,构造了控制系统的滑模变量并且合理设计神经网络的自适应规律使状态变量快速接近原点.通过稳定性分析证明了此种控制方法是全局渐近收敛的,并且对未建模动态具有强鲁棒性.数值仿真结果验证了该种控制方法的有效性,得到了阻尼器两端控制电压的变化规律.     

一种基于图像处理的万能工具显微镜测量新方法

在分析传统万能工具显微镜及现代数字化仪器优缺点的基础上,提出了一种基于图像处理的万能工具显微镜的测量方法。该方法将图像处理技术与基于FPGA和单片机的光栅测量技术相结合,在保证原有仪器的准确度高、抗干扰能力强、稳定性好、应用范围广优点的基础上,运用AutoCAD二次开发技术实现对长度、角度、圆直径等几何量的精密测量,提高了测量效率和精度,降低了操作人员的劳动强度。经过与双频激光干涉仪的测试结果进行比较,证明提出的方法具有较高的重复性和测量精度。     

Grinding force modelling for ductile-brittle transition in laser macro-micro-structured grinding of zirconia ceramics

Laser ablation accomplishes high geometrical adaptability by the use of pulsing lasers and permits the manufacture of macro-micro-structures. In this paper, a systematic approach with a laser structuring technology was devised and utilized to generate macro-micro-structured patterns on the diamond wheel surface. An experiment on zirconia ceramic grinding was performed by the macro-micro-structured wheel. The grinding force and the surface morphology were investigated. The forming mechanism of the three grinding stages was analyzed, including ductile-stage grinding, ductile-to-brittle-transition-stage grinding and brittle-stage grinding. A theoretical grinding force model was presented by taking into account the three grinding stages in laser macro-micro-structured grinding (LMMSG). In addition, the mean grinding depths were defined in grinding force modelling for the ductile area, the ductile-to-brittle-transition area and the brittle area, separately. The amount of effective diamond grains was proposed for the final grinding force model. The model revealed the connection between the grinding force and the grinding parameters. Finally, the model was verified by experiments, and the experimental results were coincided with model predictions. It was obvious that the theoretical grinding force model may be available to predict the grinding force of zirconia ceramics under the LMMSG condition. Meanwhile, the influence between the grinding parameters and the surface morphology were discussed. The experimental results verify that the three grinding stages were existed and the theoretical model was proved to be reliable.     

Optimization method to select temperature based on chemorheological and exothermal reaction of RTM

Heating mold and resin have been widely used in resin transfer molding (RTM) to improve injection and manufacturing efficiency. The unreasonable mold/resin temperatures sometimes lead to excessive viscosity of resin and premature curing, which will result in failure of the filling process. Selection of optimal mold and resin temperature has become a source of concern in the polymer industry. This article presents an optimization method to select mold and injection resin temperatures by using numerical simulation based on chemorheological and exothermal reaction of the RTM process. The results show that the optimization method has high computational efficiency for three-dimensional parts with different shapes. The selected mold/resin temperature ensures the smooth filling process, which provides a powerful tool for parameter design in polymer industry. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48245.     

TiAl合金表面激光重熔MCrAlY涂层热腐蚀性能

采用等离子喷涂技术在TiAl合金表面制备了MCrAlY涂层,并用激光重熔工艺对涂层进行处理,研究了TiAl合金、等离子喷涂MCrAlY涂层及激光重熔MCrAlY涂层850℃下75%Na₂SO₄+25%NaCl(质量分数)混合盐浸泡热腐蚀性能,分析了不同试样的热腐蚀破坏机理,并讨论了激光重熔处理对涂层热腐蚀性能的影响.结果表明,等离子喷涂MCrAlY涂层能显著提高TiAl合金的耐热腐蚀性能,经过激光重熔后可进一步提高其耐热腐蚀性能.MCrAlY涂层在高温熔盐中的热腐蚀发生的是表面氧化反应和内部硫化反应,主要生成Al₂O₃,Cr₂O₃,NiO,NiCr₂O₄,Ni₃S₂及CrS等腐蚀产物.     

基于多目标遗传算法的摆线液压马达摆线副基本参数优化

针对摆线马达摆线副基本参数优化问题,提出了基于多目标遗传算法的优化方法。并根据模糊隶属度函数从Pareto最优解集中选取最优折衷解作为摆线马达摆线副基本尺寸参数。结果表明,该方法能使马达排量提高2114%,流量脉动率降226%。     

成形砂轮超高频感应加热温度分布均匀性分析

针对单层钎焊超硬磨料成形砂轮感应加热时存在的温度分布不均匀问题,文中提出将砂轮成形面简化为相应特征成形面进行研究,借助FLUX有限元仿真软件,重点分析了线圈与导磁体的结构尺寸对凹、凸两类特征面感应加热时温度分布的影响规律,进而以燕尾槽形单层超硬磨料成形砂轮为对象,优化了钎焊用感应器结构.采用优化的感应器结构对燕尾槽型成形砂轮进行感应加热试验,利用红外热像仪测量成形面的温度分布.结果表明,该方法得到的感应器结构能够有效提高成形面超高频感应加热温度分布的均匀性,成形面各处温差在50℃以内.     

基于CAN总线和OPC技术的多轴运动控制系统

设计了一套基于CAN总线和OPC技术的柔性夹具系统。该系统采用上位机+微控制器的主从结构,上位机负责采集机床OPC服务器数据,并经过分析处理后将控制指令发送给各微控制器,微控制器接收到相应指令后执行,从而完成控制动作。系统采用分布式控制,组网灵活,可扩展性强。     

SiCp/Al复合材料超精密车削切屑形成机制及形成过程模型

通过观察切屑根部和切屑的形态及金相微观组织,采用细观分析法和金属切削理论分析法相结合,研究、分析了天然单晶金刚石（SCD）和聚晶金刚石（PCD）刀具超精密车削SiC_p/2024Al和SiC_p/ZL101A复合材料时的切屑形成机制,并建立了这两种材料的切屑形成过程模型。结果表明：切屑呈厚度准周期性变化的锯齿状;切削变形时工件材料中微裂纹的动态形成和扩展、剪切角周期变化是形成这种切屑形态的两种主要机制;该材料微观上的不均匀性、材料本身的各种缺陷以及大量不可变形增强颗粒的存在,使得切削时剪切区材料产生大量的微裂纹和微空洞,而其微观组织特性、力学性能特性以及切削时周期性的滑-停现象决定了剪切角周期变化;增强颗粒体分比、切削速度、进给量、刀具刃口半径是影响切屑形成的主要因素。     

金刚石丸片与固结磨料抛光垫研磨硅片的比较研究

采用金刚石丸片和固结磨料抛光垫两种方式研磨加工硅片,以硅片的材料去除率(MRR)和表面粗糙度(Sa)为指标对金刚石丸片和固结磨料抛光垫的研磨性能进行了评价.结果表明:固结磨料抛光垫研磨硅片的材料去除率高于金刚石丸片;研磨后硅片的表面粗糙度也优于金刚石丸片,且表面粗糙度(Sa)在中部和边缘相差不大.最后分析了研磨硅片的产物-磨屑的形状特征,得出固结磨料抛光垫研磨硅片时的塑性去除量远高于金刚石丸片.