五轴龙门数控铣床转动轴联动中的动态轨迹误差仿真分析

针对刀具两摆的五轴龙门数控铣床,对一转动轴与一平动轴联动及两转动轴联动加工圆弧时的动态轨迹误差分别进行了分析。采用D-H(Denavit-Hartenberg)法对轴的输入的进给指令位置计算公式进行了推导,并将进给指令位置输入到由动态仿真工具Simulink构建的进给伺服系统仿真模型中,得到了圆弧上动态轨迹误差的分布曲线。通过对转动轴联动加工圆弧的动态轨迹误差分析,可为五轴龙门数控铣床转动轴动态误差的检测提供指导,使得机床的检测与调整更加快速和便捷。     

空间凸轮廓面侧铣加工及最小二乘优化刀位方法

通过对空间凸轮非等价加工方式下理论刀轴轨迹曲面微分几何特性的研究，表明加工空间凸轮工作廓面必然存在法矢异向误差。为寻求加工误差最小的最佳刀轴矢量，提出了数控侧铣加工空间凸轮廓面的方法。根据实际刀轴轨迹面是直纹面的性质，以NURBS直纹面重构理论刀轴轨迹面，采用最小二乘优化方法确定侧铣加工刀位，给出了理论加工误差模型，并通过实例的数值计算和加工实验结果证明了该方法的有效性。     

Cutting-force measurement on the basis of the shaping trajectory

A new method is proposed for measuring the cutting force in a lathe. The method is based on the change in trajectory of the blank’s axis when the cutting force is applied.     

基于遗传算法的多主轴头加工空行程轨迹规划

针对多主轴头五轴机床加工时需手动规划空行程的问题,提出一种空行程轨迹自动规划方法。在机床运动学建模的基础上,针对刀位点轨迹和刀轴矢量,分别提出基于最短路径的刀位点轨迹规划和无碰撞刀轴矢量规划,将空行程规划问题转化为参数优化问题。为了简化碰撞检测,提出两级相交检测算法。通过加权系数法建立空行程规划的目标函数,并采用遗传算法求解,规划出一条无碰撞、运动时间最短、旋转轴角度变化量最小、末端轨迹最短的具有柔性的理想轨迹。在Vericut建立的仿真平台上,验证了该方法的可行性和有效性。所提方法具有拓展性,通过多次分解轨迹求取棱交点能够实现复杂工件的空行程规划。     

虚拟轴机床刀具运动轨迹的直接控制

本文提出了虚拟轴机床刀具运动轨迹的直接控制方法,该方法可根据可信息和加工工艺信息,直接生成刀具希望轨迹和虚轴运动指令,并通过虚实变换对实轴的联动控制,从而有效保证刀具轨迹与希望轨迹一致,所得结果为开发新型虚拟轴机床控制系统奠定了基础。     

四足机器人腿部运动空间和足端运动轨迹研究

机器人的单腿的运动空间及足端点运动轨迹决定了所设计的机器人的应用范围。为了研究四足步行机器人摆动腿在一定参数条件下的运动空间大小及足端的运动轨迹,通过对机器人摆动腿正运动学方程,足端点轨迹在y、z轴上对时间的函数进行计算,并将计算结果运用MATLAB软件进行仿真,不仅直观地观测到机器人的运动情况,还得到所需的数据,且以图形的形式显示出来,达到了预期目的。     

基于压电型薄膜式差动节流阀的静压主轴轴心轨迹理论研究与仿真*

提出一种压电型薄膜式差动节流阀,实现出油口压力的差动控制,并建立节流阀的数学模型,得出了流量公式。静压主轴前端采用静压轴承支撑,后端采用滚动轴承支撑,建立了静压主轴的动力学模型,且忽略静压轴承的动压效应,得到了静压轴承的油膜力以及流量公式。利用压电型薄膜式差动节流阀的差动效应,使节流阀的两个出油口分别连接静压轴承的对置油腔以期实现期望轴心轨迹,且仿真分析了期望轴心轨迹与压电陶瓷位移之间的关系,并得到了初始节流间隙与压电陶瓷位移间的关系。     

Diagnostics of metalworking machines

Diagnostics of machine-tool damage on the basis of the change in trajectory of the blank’s axis and the cutter trajectory is considered.     

圆锥刀侧铣非可展直纹面刀轴轨迹规划的特征线方法

针对圆锥刀侧铣加工非可展直纹面中复杂的刀轴轨迹规划问题,提出一种直观简便的刀轴轨迹生成方法。利用圆锥面的性质,给出法向映射曲线的定义即刀具轴线上诸点在设计曲面上的法向投影点的集合,将刀具包络面向设计曲面的逼近问题转化为每个刀位下法向映射曲线与特征线的最小二乘逼近问题,并给出刀具包络面尚未形成时单刀位下理想特征线的生成方法。用两点偏置法生成初始刀位,以此为基准,利用刚体运动学方法将刀轴位姿描述为3个回转与3个平移运动参数的函数,从而建立单刀位优化条件与6个运动参数的非显性的函数关系。采用拉丁超立方的试验设计方法求解,分析并优选计算过程中的影响因素,得到最优刀位,进而获得优化后的刀轴轨迹面。实例计算可知,刀轴优化后的包络误差显著降低,并且计算结果稳定。该方法可为非可展直纹面的圆锥刀侧铣加工提供一定的理论依据。     

Kinematical performance prediction in multi-axis machining for process planning optimization

This paper deals with a predictive model of kinematical performance in 5-axis milling within the context of high-speed machining. Indeed, 5-axis high-speed milling makes it possible to improve quality and productivity thanks to the degrees of freedom brought by the tool axis orientation. The tool axis orientation can be set efficiently in terms of productivity by considering kinematical constraints resulting from the set machine tool/NC unit. The capacities of each axis as well as NC unit functions can be expressed as limiting constraints. The proposed model relies on each axis displacement in the joint space of the machine tool and predicts the most limiting axis for each trajectory segment. Thus, the calculation of the tool feedrate can be performed, highlighting zones for which the programmed feedrate is not reached. This constitutes as an indicator for trajectory optimization. The efficiency of the model is illustrated through examples. Finally, the model could be used for optimizing process planning.     

基于显式有限元的转子不平衡与轴承故障耦合分析

为分析转子不平衡与轴承故障耦合振动特征及产生机理,在对转子不平衡与轴承故障耦合状态下受力分析的基础上,基于虚位移原理的增广拉格朗日法建立轴承运动控制方程,运用LS-DYNA建立转子-轴承系统二维显式动力学有限元模型,分析了故障耦合状态下轴承振动加速度、转子轴心运动轨迹,探明了转子不平衡-轴承缺陷耦合故障冲击响应特征及转...     

关节空间样条的连续点位运动规划算法

为了提高工业机器人的运动平稳性和快速性,保证机器人在走曲线时能够准确到达各示教点并且实现平滑过渡,提出一种基于关节空间样条的连续点位运动规划算法。以关节空间的单个轴为例,从一般三阶S曲线轨迹出发,为了保证规划得到的加速度不跳变以及样条曲线能够保形,在两个相邻示教点之间插入n个中间点,将一段轨迹分为n+1段,根据该关节起点和终点的位置、速度和加速度以及插入点位置、速度、加速度连续的边界条件,可以得到新的规划轨迹。最后通过实验比较验证,该规划算法能够快速实现过程点的准确到达并且加速度没有跳变、曲线能够保形,具有实际推广价值。     

Short note on parallel illumination in the TEM

Parallel illumination conditions are required for several experiments in the transmission electron microscope (TEM). The image rotation induced by the helical trajectory of electrons passing through the magnetic field of the TEM lenses inevitably induces an inclination of the beam relative to the optical axis in the object plane--even for an electron which travels parallel to the optical axis in the far field. This angle (shear angle) is vectorially added to the convergence angle; it depends both on the distance to the optical axis and the magnetic field. By using a beam tilt compensation method, the minimum shear angle is found to be of the order of 1 mrad for a field of view of 2 microm in a 200 kV TEM. In practice, "parallel illumination" can only be obtained for fields of view 1 microm.     

基于往复压缩机轴心轨迹特征的故障诊断方法研究

往复压缩机的故障诊断一直以来都是研究工作的重点问题,对其关键运动部件的监测诊断更是研究的热点之一.当往复压缩机发生运动部件磨损、撞缸等故障时,活塞杆的运行状态会发生改变,进而引起活塞杆轴心轨迹的变化.因此,提出了一种基于活塞杆轴心轨迹的往复压缩机智能诊断方法.首先,文章利用改进的离散点轮廓包络方法提取活塞杆轴心轨迹特征...     

供气压降下气体轴承-转子系统瞬态特性流固耦合分析

为研究供气压力波动对气体轴承-转子系统瞬态特性的影响,采用一种流固耦合仿真与实验相结合的方法,对空载及加载下气体轴承-转子系统在不同转速和供气压力下降时的转子下端偏移、轴心轨迹等变化规律进行了研究。结果表明：供气压力以斜坡形式下降时转子下端偏移理想轨迹的距离呈现波浪式变化,且工频条件下的轴心轨迹重复性变差;加载时供气压降前后转子下端偏移差值明显高于空载状态;供气压降前后转子下端偏移差值随着加载力和转速的增大而增大。     

Optimal curvature-smooth transition and efficient feedrate optimization method with axis kinematic limitations for linear toolpath

In industrial areas, the machining performance with linear G01 code is a crucial indicator to evaluate the computer numerical control (CNC) systems and many researchers have presented various methods to deal with the corner tracking issue. However, the axis jerk limitations are not satisfied well and the different axis kinematic limitations are not considered in most researches, which will reduce the machining efficiency and machining quality simultaneously. In this paper, a novel method including trajectory planning, feedrate scheduling, and interpolating is proposed to obtain better machining quality and higher machining efficiency. In trajectory planning, a B-spline curve is utilized to smooth the linear toolpath and obtain a curvature-smooth trajectory, which is third-order geometry continuous. Thereby, a time-optimal method for the geometric continuous trajectory is proposed based on linear programming algorithm in the feedrate scheduling and the bounded multi-constraints, including axis velocity, axis acceleration, axis jerk, and feedrate. Moreover, it can be seen that the proposed method is near Bang-bang control. To reduce the computation time of the optimal numerical method, an efficient method with a look-ahead window around the transition B-spline curve is applied. In the interpolation stage, a novel interpolation method about arc-length is proposed to improve computation efficiency. Finally, simulation and experiment are conducted to show superiorities of the proposed method to the already existing approaches. The results show that the cycling time of the proposed method is reduced by more than 7% than G² method and 20% than G³ method with better contour performance.     

柴油加氢装置循环氢压缩机振动故障原因分析

通过对410Mt／a柴油加氢装置循环氢压缩机K102振动故障原因分析,从机组振动频谱、轴心轨迹入手,详细阐述了离心式压缩机组振动的形成机理以及各种振动现象下的频谱特征,对该机组振动原因做出了较为准确的判断,快速顺利地解决了该设备故障。     

Indirect Adaptive Robust Trajectory Tracking Control of Hard Rock TBM with Load Variation of Tunneling Face

Posture adjustment of open-type hard rock tunnel boring machine(TBM) can be achieved by properly adjusting the hydraulic pressure of gripper cylinder and torque cylinders. However, the time-varying inhomogeneous load acting on tunneling face of TBM and complex stratum working condition can cause the trajectory deviation. In this paper,the position and posture rectification kinematics and dynamics models of TBM have been established in order to track the trajectory. Moreover, there are uncertain parameters and uncertain loads from complex working conditions in the dynamic model. An indirect adaptive robust control strategy is applied to achieve precise position and posture trajectory tracking control. Simulation results show when the position deviation only occurs in Y-axis and the current orientation is parallel with the designed axis, the deviation can be corrected by controlling the pressure of gripper cylinder and the actual trajectory meets the designed axis when TBM is pushed forward 0.14 m in X-axis. If the deviation only occurs in Z-axis, then the deviation can be corrected by controlling torque cylinders. If the position deviation occurs both in Y-axis and Z-axis at the same time, the pressure of gripper cylinder and torque cylinders should be controlled at the same time to rectify the deviation. Simulation results are shown to illustrate the e ectiveness and robustness of the proposed controller. This research proposes an indirect adaptive robust controller that can track the planned tracking trajectory smoothly and rapidly.     

基于球杆仪的直线轴位置相关误差辨识研究

针对多轴机床空间误差检测及辨识方法成本高、时间长等问题,提出一种新的基于球杆仪测试的直线轴位置相关几何误差辨识方法。分别建立各平面内轴运动误差模型,并采用多项式对误差元素预拟合,以常规的三平面圆弧轨迹测量获取误差数据,并基于最小二乘法求解拟合系数,替代直接对误差元素具体数值求解的传统方法,实现对各直线轴位置相关误差元素的辨识。通过实验验证了辨识结果的正确性和有效性,该方法对机床直线轴误差辨识、补偿具有参考价值。     

考虑控制电信号中间量的机床运动控制误差数据驱动建模方法

现有数据驱动的机床运动控制误差建模方法通常使用端到端的模型,即通过机器学习算法直接构建参考轨迹信息(速度、加速度等)与伺服误差之间的模型,以降低建模复杂度。然而,该方法忽视了控制电信号对运动控制系统非线性扰动的反映,而导致建立的模型精度受限。为解决此问题,提出了一种使用控制电信号作为中间量的数据驱动运动控制误差建模方法。该方法采集参考轨迹信息(速度、加速度、急动度等)、控制电信号、跟踪误差以及构造的换向特征,构建并训练基于参考轨迹信息的控制电信号预测网络,以及基于电信号和参考轨迹信息的运动控制误差预测网络,利用控制电信号这一中间量有效反应系统所受非线性扰动的特点,实现了高精度的运动控制误差数据驱动建模。在实际验证测试时,将参考轨迹信息输入电信号预测网络,而后将得到的预测控制电信号和参考轨迹信息输入跟踪误差预测网络,即可实现运动控制误差的预测。通过实验对所提出的建模方法进行了验证,所提出方法相对于传统的端到端建模方法,运动控制误差的预测精度在X轴和Y轴分别提升16.33%和20.42%,误差补偿后运动控制轮廓精度相较于未补偿提升85.59%,验证了所提出方法的可行性。