运动轨迹对抛光误差的影响分析和轨迹优化研究

针对现有光学加工抛光头运动方式由于光栅形或螺旋形等对称扫描方式带来的运动轨迹间的迭代误差,提出随机轨迹抛光运动方式.随机轨迹方法通过随机轨迹算法随机生成镜面离散点的抛光顺序和抛光轨迹,采用随机轨迹驻留时间补偿方法控制镜面离散点的驻留时间,对各个点进行相应大小的材料去除.实验结果显示,随机轨迹方法产生的抛光运动轨迹表现为...     

基于环摆式双面抛光法加工预测模型的去除均匀性研究

针对环摆式双面抛光难以建立稳定去除函数并进行加工面型预测这一问题,提出了基于磨粒运动学的环摆式双面抛光加工预测模型,并通过预测模型分析不同参数影响下元件表面去除均匀性,针对不同特征面型给出优化策略以指导加工实验。首先,根据环摆式双面抛光机理,探究了环摆式双面抛光中影响去除均匀性的主要因素,提出了元件上、下表面磨粒运动学模型,结合Preston方程给出了基于磨粒运动学的环摆式双面抛光去除均匀性预测模型。根据实际加工工况,分析了不同抛光均匀性影响因素下的磨粒轨迹分布与抛光去除非均匀性,最后通过加工实验验证环摆式双面抛光加工预测模型。实验结果表明：环摆式双面抛光加工预测模型的预测结果与实际加工结果基本吻合,其面型去除特征相同。元件上表面是元件去除非均匀性的主要来源,通过改变中心偏心距、径向摆动距离等参数能改变元件上表面的去除非均匀性,从而影响元件整体面型特征,并实现基于预测模型指导下元件表面面型的快速收敛。     

非固定环带随机双面抛光技术研究

提出了一种基于平移偏摆运动的非固定环带随机双面抛光的方法,通过设计平移偏摆装置使得工件运动方式脱离固定环带的限制,借助随机性运动进行迭代,解决了行星式双面抛光等固定环带抛光过程中产生的周期性轨迹问题;通过优化运动方式组合,在随机性运动叠加情况下实现了大口径超薄元件面形稳定收敛控制。与行星式双面抛光相比,不仅面形精度更好,而且没有明显的周期性加工痕迹。该方法可以应用到对表面激光损伤阈值有特殊要求的超薄件批量生产当中。     

平面光学元件研磨抛光磨粒运动轨迹曲率研究

为提高研磨抛光加工表面质量,利用Matlab软件编制程序对不同参数下轨迹曲线曲率进行计算分析。结果表明,转速比对磨粒运动轨迹曲线曲率影响很大;相同转速比下的曲线曲率呈现周期性变化,曲率变化幅值很小;磨粒径向距离越大,曲率变化越剧烈,工件边缘处容易产生曲率突变;考虑到对磨粒径向距离的影响,偏心距不宜太大或太小。同时,磨粒初始角度对磨粒轨迹曲线曲率形状没有影响。该研究可为研磨抛光设备的设计提供理论指导。     

3mm厚大口径超薄元件双面抛光工艺北大核心CSCD

基于环摆双面抛光技术,研究了3mm厚大口径超薄元件的双面抛光加工工艺。通过对双面抛光原理的分析,对转速比、抛光垫面形、抛光液等工艺参数上作了优化,并通过加工模拟进行验证。通过工件环分离器减薄技术解决了3mm厚超薄元件的装夹问题。在SYP152双面主动抛光机上进行了加工工艺实验,通过调节转速比实现3mm厚大口径超薄元件面形的高效收敛,验证了加工的可行性,并且达到了面形精度优于1.5λ(λ=632.8nm)、表面粗糙度优于1nm的技术水平。     

足球异常运动与其实际应用的MATLAB模拟

模拟并研究了马格努斯效应对足球的运动轨迹和进球概率的影响.首先通过受力分析建立起飞行中足球的质心运动方程,利用MATLAB模拟得到弧线球的运动特点:相比于理想的抛物线轨迹,弧线球的轨迹是一条不共面且不对称的弧线.然后基于蒙特卡罗算法,分析了利用弧线球进球的出射速度分布情况,并进一步得到了本文所考虑区域的有无马格努斯效应作用时进球概率的分布及差值分布,发现这两种情况下进球概率的相对大小呈现以球门为中心的交替辐射带状分布.     

在双抛机上实现板材单面抛光的加工技术

目前在光学冷加工市场有一定量的单面抛光板材的需求量,由于这种零件大多在要求只有一个面抛光的同时,对抛光面的面型有较高的要求,采用传统的粘接剂上盘在单轴抛光机上进行单面抛光的方法,由于拆胶后零件的应力变形,无法得到要求较高的面型。双面抛光技术由于两个面同时加工,可以很好地消除抛光面的应力问题,因此在薄板型零件加工中可以得到较好的面型,但只能得到双面同时抛光的零件。介绍了几种在双面抛光机上实现高面型精度要求的单面抛光板材的加工方法。     

双轴式研磨抛光中抛光盘相对位置对去除量的影响研究

为了了解在抛光过程中抛光盘位置对光学元件面形的影响,对一种双轴式平面研磨抛光运动过程进行了分析。从Preston方程出发,推导了去除函数的表达式,研究了抛光盘的摆幅及偏心距离对元件的去除量分布的影响。通过定量计算得知,在加工转速不变的情况下,增大抛光盘的摆幅,元件不同圆周上的去除量也不同。增大偏心距,元件的去除量增大,不论抛光盘相对元件的位置如何改变,回转中心的去除量总是最大。     

激光驻波场中Cr原子运动轨迹与汇聚沉积的分析

利用半经典模型，从铬原子在激光驻波场中的运动方程出发，通过数值解方法模拟了铬原子在驻波场中的运动轨迹，并分析了原子的纵向速度分布和准直程度及球差对沉积条纹结构的影响，同时也讨论了基片摆放位置对沉积条纹结构的影响，并通过实验得到了纳米光栅条纹结构. 关键词： 激光驻波场 原子沉积 运动轨迹 沉积分布     

自动化控制下机械手臂运动轨迹研究

对机械手臂运动轨迹进行优化控制,能改善机械手臂的自动控制性能。为了提高机械臂的控制稳健性,提出一种基于变结构模糊PID控制的机械手臂运动轨迹优化控制模型。首先采用末端效应逆运动学模型构建机械手臂的运动规划约束参量数学模型,采用七自由度运动空间重构方法建立机械手臂运动的动力学方程。然后通过纵向定常运动,分析建立机械手臂整定控制目标函数,求解机械臂在抓取作业过程中的最佳导引控制律,采用变结构模糊PID控制方法进行运动轨迹的误差修正,实现机械臂自动控制优化。最后通过仿真实验进行控制性能测试,结果表明,采用该方法进行机械手臂运动轨迹控制的精度较高,对机械臂位形变化轨迹的预测准确性较好。     

光学镜片平面行星式研磨加工关键技术研究

在平面行星式研磨加工过程中,研磨盘磨损的均匀性与光学镜片的研磨质量有密切关系。通过对光学镜片在平面行星式研磨加工过程中的运动规律进行分析,建立了差动轮系条件下工件运动的轨迹和速度计算模型,开发了Matlab仿真程序。结合生产实际,对行星轮系条件下工件运动的轨迹和速度进行了仿真,确定了研磨机速比对研磨盘磨损均匀性的影响规律:当速比I1-1.5时,镜片的运动轨迹在较短时间内遍布研磨盘各处,研磨盘得到均匀磨损,加工质量和加工效率较高。基于仿真结果,通过优化工艺参数,获得了厚度一致性小于0.002 mm,平行度小于0.002 mm的高质量光学镜片。     

抛光垫磨损非均匀性研究

抛光垫是化学机械抛光的重要组成部分,其磨损的非均匀性对被加工工件面型精度和抛光垫修整有重要影响。基于直线摆动式抛光方式,研究了抛光过程中抛光垫与工件的相对运动,建立了抛光垫磨损模型,分析了抛光工艺参数对抛光垫磨损及均匀性的影响。研究结果表明,工件与抛光垫的转速比为1.11,正弦偏心直线摆动形式,摆动幅度系数为2,摆动频率系数在0.1~0.2之间,抛光垫表面磨损更均匀,并根据抛光垫表面磨损特性优化了抛光垫形状。优化的抛光垫具有更好的面型保持性,延长了修整间隔,为抛光工艺设计提供理论指导。     

抛光工艺参数对熔石英元件低频面形精度的影响

根据工件与抛光盘的相对运动关系及熔石英元件抛光加工材料去除模型,系统分析了转速比和偏心距等参数对材料去除函数的影响。通过理论分析和抛光加工实验,研究了不同工艺参数对低频段面形精度的影响规律。利用高分辨率检测仪器对熔石英元件低频面形误差进行了检测,优选出较佳的抛光工艺参数组合,并进行了相应的实验验证,提出了提高光学元件抛光加工低频面形质量的相应措施。     

Simulation of ball motion and energy transfer in a planetary ball mill

A kinetic model is proposed for simulating the trajectory of a single milling ball in a planetary ball mill, and a model is also proposed for simulating the local energy transfer during the ball milling process under no-slip conditions. Based on the kinematics of ball motion, the collision frequency and power are described, and the normal impact forces and effective power are derived from analyses of collision geometry. The Hertzian impact theory is applied to formulate these models after having established some relationships among the geometric, dynamic, and thermophysical parameters. Simulation is carried out based on two models, and the effects of the rotation velocity of the planetary disk and the vial-to-disk speed ratio ω/Ω on other kinetic parameters is investigated. As a result, the optimal ratio ω/Ω to obtain high impact energy in the standard operating condition at = 800 rpm is estimated, and is equal to 1.15.     

Dynamic characteristics of the herringbone planetary gear set during the variable speed process

In this study, a dynamic model for herringbone planetary gears is proposed which can be applied in the dynamic analysis of variable speed processes (including acceleration, deceleration, and large speed fluctuation process, etc.). The dynamic responses of the acceleration process of an example of a herringbone planetary gear set are simulated in cases where the profile error excitations are ignored and included. The phenomenon of tooth separations can be observed as the rotating speed increases in the simulation, and the effect of the profile error excitations on the phenomenon is also investigated. Furthermore, the effects of the profile error excitations on the vibrations and dynamic meshing forces are investigated before and after the appearance of tooth separations. Moreover, the dynamic characteristics of the herringbone planetary gear set are also compared with that of the spur/helical herringbone planetary gear set briefly. Finally, some advice for the design of planetary gear sets is given to avoid the phenomena of tooth separation and tooth back contacts and suppress the vibrations and dynamic meshing forces.     

环带抛光技术材料去除理论模型研究

为了更加完善环带抛光技术并指导加工,根据Preston方程建立了材料去除量的理论模型。考虑到环带抛光技术中的诸影响因素,如抛光盘与工件之间的转速比、偏心距及压强分布等参数,建立材料去除量与各影响因素之间的相互关系的数学模型。理论分析和实验结果表明：材料的去除效率随转速比和偏心距增加而增大,转速比越接近于1时,磨削越均匀;工件露边时,工件露出部分材料的去除效率急剧下降。通过对该理论模型中的相关技术参数研究来完善环带抛光技术,有效地提高抛光的效率及稳定性。     

Effect of different heating methods on deformation of metal plate under upsetting mechanism in laser forming

In a laser forming process, different forming mechanisms have different deformation behaviors. The aim of laser forming is to acquire plane strain under an upsetting mechanism, while a plate undergoes a small bending deformation. In some industrial applications, the bending strain should not occur. To achieve high-precision forming, the deformation behaviors of a metal plate when an upsetting mechanism plays a dominant role are studied in the paper. Several heating methods are proposed to reduce the plane strain difference along the thickness direction and little bending deformation resulting from a small temperature difference between the top and bottom surfaces of the plate. The results show that negligible bending deformation and a uniform plastic plane strain field can be obtained by simultaneously heating the top and bottom surfaces with the same process parameters. A conventional scanning method needs a larger spot diameter and slower scanning speed under the upsetting mechanism, but a smaller spot diameter and quicker scanning speed may be selected using the simultaneous heating method, which can greatly widen the potential scope of process parameters.     

Complex signal analysis for wind turbine planetary gearbox fault diagnosis via iterative atomic decomposition thresholding

The vibration signals from complex structures such as wind turbine (WT) planetary gearboxes are intricate. Reliable analysis of such signals is the key to success in fault detection and diagnosis for complex structures. The recently proposed iterative atomic decomposition thresholding (IADT) method has shown to be effective in extracting true constituent components of complicated signals and in suppressing background noise interferences. In this study, such properties of the IADT are exploited to analyze and extract the target signal components from complex signals with a focus on WT planetary gearboxes under constant running conditions. Fault diagnosis for WT planetary gearboxes has been a very important yet challenging issue due to their harsh working conditions and complex structures. Planetary gearbox fault diagnosis relies on detecting the presence of gear characteristic frequencies or monitoring their magnitude changes. However, a planetary gearbox vibration signal is a mixture of multiple complex components due to the unique structure, complex kinetics and background noise. As such, the IADT is applied to enhance the gear characteristic frequencies of interest, and thereby diagnose gear faults. Considering the spectral properties of planetary gearbox vibration signals, we propose to use Fourier dictionary in the IADT so as to match the harmonic waves in frequency domain and pinpoint the gear fault characteristic frequency. To reduce computing time and better target at more relevant signal components, we also suggest a criterion to estimate the number of sparse components to be used by the IADT. The performance of the proposed approach in planetary gearbox fault diagnosis has been evaluated through analyzing the numerically simulated, lab experimental and on-site collected signals. The results show that both localized and distributed gear faults, both the sun and planet gear faults, can be diagnosed successfully.