基于直线逼近的曲线插补算法研究

插补算法是数控技术的核心。文中研究了插补算法中三种典型的基于直线逼近的曲线插补算法,通过其在MATLAB上进行分析,得出等直线逼近的插补算法和等步长逼近插补算在误差上优于等误差逼近插补算法,等误差逼近插补算法在走刀次数优于等直线逼近的插补算法和等步长逼近插补算,同时它们在算法在运算上也比较简单,更加具有普遍意义。     

插补算法的误差及实时性研究

插补计算是数控系统最重要的运算工作，如何正确地选用插补算法，以保证插补运算的实时性和精度是开发数控系统的关键；通过对插补误差的分析，提出一种计算插补误差的算法——均差法，建立了均差法的数学模型，并利用均差法计算出DDA插补和时间分割插补的误差及插补计算时间。     

逐点比较插补法的改进

透点比较法是目前数控机床上用得比较多的一种插补方法，但因每一次插补计算只有一个坐标进给，插补的阶梯状比较明显，插补误差比较大。为了减小插补误差、提高插补精度和速度，对传统的插补方法进行了改进。     

参数曲线的恒速通用插补原理与实例分析

阐述了参数曲线恒速插补的通用原理,同时讨论了廓误差近似计算方法。以摆线为例推导了相庆的插补公式和轮廓误差近似计算公式。最后通过VISUAL LISP编程进行插补模拟,表明该插补原理具有无累计误差、恒速进给以及轮廓误差易于控制的特点,而且该算法插补功能的开发和应用前景十分广阔。     

三点圆法参数自适应插补算法

以三点定圆替代传统的二点定线,以圆弧插补替代直线插补,以参数中间点替代极值点,简化插补误差的计算,通过控制最大插补误差来修正插补参数,实现参数的自适应.解决了三点圆法插补过程中圆弧顺逆判断、插补误差的计算.编写算法流程框图,并以椭圆曲线为例进行程序的编制和验证.通过分析可知,该算法能减少插补节点,提高插补质量和插补效率,具有较好的应用性、通用性和推广性.     

五坐标数控加工插补误差的刀触点加密控制方法

对五坐标数控加工插补误差的产生原理进行了深入分析,探讨了在各种加工允差条件下插补误差的产生原理,并提出了刀触点自适应加密的插补误差控制方法,为减小五坐标数控加工的插补误差、提高加工精度和质量提供了参考。     

平面和空间螺线的恒速插补算法

基于参数曲线恒速插补机理分析,建立了平面和空间螺线的恒速插补算法,讨论了插补误差及其有效近似计算,通过AutoLISP编程进行实例插补模拟。结果表明该插补算法无累计误差,具有恒速进给、插补精度易于控制等特点,便于现代通用PC微机数控系统进行开发和应用。     

复杂曲面加工中等距双NURBS刀具路径高效插补方法

为降低复杂曲面加工中采用相同节点向量生成等距双非均匀有理B样条(NURBS)刀具路径的插补误差并提升插补实时性,提出一种基于改进协同进化遗传算法及三阶导出Newton型参数计算的双NURBS刀具路径插补方法。基于误差控制选取部分刀具中心点和刀轴点离散数据,并采用同一节点向量构造双NURBS曲线,利用协同进化遗传算法调整刀轴点曲线的权重值,以降低曲线的拟合误差从而提高插补精度。实际插补时,采用三阶导出Newton方法提高插补参数的计算精度,以进一步降低插补误差,减少参数计算时间。仿真实验表明,与其他方法相比,该算法能够有效降低插补误差、提升插补实时性。     

新型并联机床数控系统插补算法的研究

提出一种用于新型并联机床的粗、精插补策略和算法 ,粗插补采用直接对加工曲面进行插补的方法。以NURBS曲线为例 ,运用合理计算方法推导出粗插补计算公式 ,并对粗、精插补进行了误差分析。插补实例结果表明 ,该插补算法具有恒速进给、加工表面轮廓误差易于控制等特点     

最小误差插补方法的研究

在传统的逐点比较插补方法的基础上,介绍了一种新的插补方法———最小误差插补方法,这种插补方法可使插补误差控制在±２／２ｔ 范围内,对于数控加工有着实际的意义,文中给出了相应的简单易实现的算法。     

基于Stewart平台的六轴并联机床的研究

分析了国内外并联机床的研究现状,并阐述了并联机床相对于传统机床的优势。从总体上介绍了研究并联机床所涉及的主要内容。基于Stewart平台模型,提出改进的运动平台机构;根据平台初始位姿和目标位姿,通过逆向解法,计算杆件的伸缩长度;借鉴成熟控制算法,基于“PC＋运动控制卡”控制系统,设计控制规则,综合逆向求解参数,编写控制系统程序代码。     

面向新型并联机床的NURBS曲面直接插补算法研究

提出了以四自由度空间并联机构作为主进给机构 ,辅以双向移动工作台实现多坐标数控加工的一种新型并联机床的配置方案。推导了并联机床位置、速度逆解模型 ,设计了面向该并联机床的CNC系统方案。构造了由刀具轨迹计算、位置与速度逆解模型和PVT细插补模式相结合的NURBS曲面直接插补算法 ,并讨论了CNC系统方案实施中的关键技术     

Implementation of frequency-shaped tip reference in conjunction with learning controller for improved tip-tracking control

In the flexible manipulator control, tip-tracking control of flexible manipulator results in non-colocated control problem, which has a non-minimum phase dynamic characteristic. The level of tip-tracking performance in the non-colocated control system depends on the characteristics of the tip reference trajectory to be followed, as well as on the characteristics of the flexible manipulator system itself. In a previous research the use of a tip reference trajectory, filtered by a properly designed time-delay command shaping filter, has been proposed and a multirate repetitive learning control (MRLC) has been used as the tip-tracking controller. The practical implementation of this approach, however, requires estimation of the tip position, which is not easy to obtain. In this paper, a practical implementation of the approach is considered and the tip position is estimated with a fourth-order Kalman filter. The experimental results show that, with the use of Kalman filter, the proposed scheme results in a drastic reduction in residual tip vibrations and the required actuation effort. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Joo Han Park received his B.S. and M.S. degrees in mechanical engineering from the Kyung Hee Univ., Korea, in 2005 and 2007, respectively. He is currently a Ph.D. candidate in Kyung Hee Univ., Korea. His research interests include robotics and vibration control. Soon Geul Lee received his B.S. degree in Mechanical Engineering from Seoul National Univ. in 1983 and M.S. degree from KAIST in 1985. He received his Ph.D. degree in mechanical Engineering from U. of Michigan, Ann Arbor in 1992. He is currently a Professor at the Dept. of Mechanical Engineering in Kyung Hee Univ., Korea. Sungsoo Rhim received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National Univ., Korea, in 1990 and 1992, respectively. He received his Ph.D. degree in mechanical engineering from Georgia Institute of Technology in 2000. He is currently an Assistant Professor at the Dept. of Mechanical Engineering in Kyung Hee Univ., Korea.     

一种新型运动副及其在并联机床上的应用

提出了一种基于新型运动副——复合球铰的虚拟轴机床,它是由5-SPS分支组成的并联机构,其中3个分支汇交于一个三重球铰,另2个分支汇交于一个二重球铰,两个球铰固接在一起形成一个复合球铰,代替了并联机构的活动平台,而且机床主轴位于复合球铰中心线上。这种基于复合球铰的5个分支新型虚拟轴机床与基于Stewart平台机构的6个分支的虚拟轴机床相比具有同样多的实用自由度,并且机床结构简单、解耦,其正反解计算及控制亦相对简单。探讨了5分支机床的结构形式,尤其对关键结构——复合球铰的结构,机构位置反解,以及一定姿态下的可达工作空间进行了分析和计算。这种新型虚拟轴机床在空间曲面加工领域将有着广泛的应用前景。     

一种并联机器人误差综合补偿方法

针对并联机器人轨迹规划和轨迹跟踪过程中,同时存在机构误差引起的期望轨迹与理想轨迹之间的偏差和非线性摩擦、负载变化等扰动因素引起的动态误差,提出一种并联机器人误差综合补偿方法:在轨迹规划过程中,基于并联机器人位姿误差模型将位姿误差补偿转化为驱动杆参数组合优化问题,进而利用粒子群算法寻优驱动杆参数,修正并联机器人期望轨迹;在轨迹跟踪过程中,设计基于自适应迭代学习控制算法的动态误差补偿策略,实现对期望轨迹的有效跟踪。在Stewart平台下基于ADAMS和Matlab进行仿真试验,在轨迹规划和轨迹跟踪过程中,分别修正期望轨迹偏差并补偿轨迹跟踪动态误差,实现并联机器人误差综合补偿。进一步,基于混联机床进行工件加工试验,验证方法对于提高并联机器人工作精度的有效性。     

Prototyping a robotic dental testing simulator

A parallel robot based on the Stewart platform is being developed to simulate jaw motion and investigate its effect on jaw function to test the wearing away of dental components such as individual teeth, crowns, bridges, full set of dentures, and implant-supported overdentures by controlling chewing motion. The current paper only describes the comparison between an alternative configuration proposed by Xu and the Stewart platform configuration. The Stewart platform was chosen as an ideal structure for simulating human mastication as it is easily assembled, has high rigidity, high load-carrying capacity, and accurate positioning capability. The kinematics and singularities of the Stewart platform have been analysed and software developed to (a) test the control algorithms/strategy of muscle movement for the six degree of freedom of mastication cycle and (b) simulate and observe various design options to be able to make the best judgement in product development. The human replica skull has been analysed and reverse engineered with further simplification before integration with the Stewart platform computer-aided design (CAD) to develop the robotic dental testing simulator. Assembly modelling of the reproduced skull was critically analysed for good occlusion in CAD environment. A pulse-width modulation (PWM) circuit plus interface was built to control position and speed of the chosen actuators. A computer numerical control (CNC) machine and wire-electro-discharge machining (wire EDM) were used to manufacture the critical parts such as lower mandible, upper maxilla, and universal joints.     

一种新颖的6自由度并联机床结构型式及其局部各向同性分析

针对以Stewart平台为原型的6自由度并联机床各项同性和工艺性差等问题,提出一种新颖的6－DOF并联机床结构,应用并联机器人机构学理论,论证了该种结构型式的并联机床在其工作空间内存在速度和力各向同性位姿,具有最佳的运动和力传递性能,选择各向同性位姿为机床初始装配位姿,改进了机床的结构,改善了装配工艺性。     

一种串并联式Stewart平台机构的误差分析

设计了一种由双级并联机构组成的位姿精调试验平台 ,分析了平台上每个铰链点的位置误差和各支链的长度误差对试验平台末端执行器运动精度的影响 ,建立了试验平台末端误差的数学模型。仿真结果表明 ,该机构的位姿误差具有线性叠加性 ,这种串并联平台末端误差的相对变化量很小 ,基于该构型的试验平台可达到较高运动精度。     

A Cutter Orientation Modification Method for the Reduction of Non-linearity Errors in Five-Axis CNC Machining

In the machining of sculptured surfaces, five-axis CNC machine tools provide more flexibility to realize the cutter position as its axis orientation spatially changes. Conventional five-axis machining uses straight line segments to connect consecutive machining data points, and uses linear interpolation to generate command signals for positions between end points. Due to five-axis simultaneous and coupled rotary and linear movements, the actual machining motion trajectory is a non-linear path. The non-linear curve segments deviate from the linearly interpolated straight line segments, resulting in a non-linearity machining error in each machining step. These non-linearity errors, in addition to the linearity error, commonly create obstacles to the assurance of high machining precision. In this paper, a novel methodology for solving the non-linearity errors problem in five-axis CNC machining is presented. The proposed method is based on the machine type-specific kinematics and the machining motion trajectory. Non-linearity errors are reduced by modifying the cutter orientations without inserting additional machining data points. An off-line processing of a set of tool path data for machining a sculptured surface illustrates that the proposed method increases machining precision.     

数控机床运行可靠性控制技术方案分析

可靠性是评估数控机床运行效率和经济性的关键性指标,因此,要结合数控机床运行情况建立多元控制方案,利用对比分析的方法,从保养、运行状态以及工作环境等关键点出发,全面阐释影响数控机床运行可靠性的因素,并通过建模的方式全面解读数控机床运行可靠性控制要求,打造实时性监控平台,以便于能全面了解数控机床运行情况,提高数控机床应用运...