基于零相位误差跟踪控制器的轮廓误差交叉耦合控制

针对高精密轮廓加工，在分析系统轮廓误差的基础上，通过减小跟踪误差来间接减小轮廓误差，提出了将交叉耦合控制器和零相位误差跟踪控制器相结合的控制策略。交叉耦合控制器用以增加各轴之间的匹配程度，以减小轮廓误差；零相位误差跟踪控制器作为前馈跟踪控制器，提高了快速性，使系统实现准确跟踪。仿真结果表明所提出的控制方案是有效的，能达到良好的轮廓跟踪效果，从而提高了轮廓加工精度。     

基于MPC和CCC的XY平台鲁棒跟踪控制

针对XY平台伺服系统在位置定位过程中由于扰动、摩擦等因素造成的轮廓误差的问题,提出将模型预测控制器(MPC)和交叉耦合控制器(CCC)相结合的控制方法.预测控制器通过多步测试、滚动优化和反馈校正等方法对XY平台单轴的定位精度进行优化,减小XY平台系统的跟踪误差.同时采用交叉耦合控制器对系统进行解耦,以解决两轴之间的耦合问题,进而减小系统的轮廓误差,提高系统的轮廓精度.最后通过仿真实验,验证所提出的控制方案是可行的,既保证了系统的鲁棒性,又提高了系统的跟踪精度,进而改善系统的轮廓加工精度.     

通过直线伺服鲁棒跟踪控制方法提高轮廓加工精度

为了减小零件加工的轮廓误差,提出了一种采用直线伺服驱动的零相位跟踪控制器(ZPETC)和干扰观测器 (DOB)相结合的鲁棒跟踪控制策略。零相位误差跟踪控制器作为前馈跟踪控制器,提高了快速性,使系统实现准确跟踪;基于干扰观测器的鲁棒反馈控制器补偿了外部扰动、未建模动态、系统参数变化和机械非线性等不确定因素,并根据预测到的干扰信息对各轴进行补偿以消除干扰对系统的影响,从而保证了系统的强鲁棒性能。仿真结果表明所提出的控制方案是有效的,既能实现完好跟踪,又有较强的鲁棒性能,从而提高了轮廓加工精度。     

基于动态轮廓误差估计的三轴运动平台NNLARC控制

在直线电动机驱动三轴运动平台中,为提高轮廓加工精度,需要解决两个主要问题,即轮廓误差估计和轮廓误差控制。采用基于牛顿极值搜索算法的动态轮廓误差估计的方法,建立更为精确的轮廓误差模型。由于永磁同步直线电动机(PMLSM)易受外部扰动和摩擦力等因素影响,为使系统具有良好的跟踪性能和抗干扰性能,采用神经网络学习的自适应鲁棒控制(NNLARC)进行单轴位置控制器的设计,削弱各种因素对于系统性能影响。另外,采用位置环交叉耦合控制器,解决三轴间的动态特性不匹配问题,进一步减小轮廓误差。仿真结果表明,所设计的方法能有效提高系统的加工精度和鲁棒性。     

基于交叉耦合与迭代学习的伺服系统运动控制研究

针对数控机床进给伺服系统各轴动态响应不一致,导致零件加工精度降低的问题,对数控机床进给伺服系统运动控制进行了研究。采用了迭代学习控制与交叉耦合结构相结合的控制方法,设计了进给伺服系统单轴位置环的迭代学习控制器,抑制了单轴跟随误差,设计了多轴的变增益交叉耦合迭代学习控制器,来抑制多轴轮廓误差;利用在MATLAB/SIMULINK环境中搭建的仿真模型,对三叶玫瑰曲线轨迹进行了跟踪验证;将所设计的控制器与其他控制方法进行了对比分析。研究结果表明:与其他控制方法相比,所设计的控制器跟踪曲线的最大轮廓误差和平均轮廓误差都得到了降低,证明所设计的单轴和多轴运动控制器能够实现降低轮廓误差,提高零件加工精度的目的。     

基于双NURBS参数混合插补算法的五轴联动交叉耦合控制器研究

针对零件复杂曲面高速高精度数控加工的需求,分析五轴联动数控加工系统刀具运动轨迹中的轮廓误差和方向误差,建立了该轮廓误差和方向误差的实时计算模型,从而得出系统跟踪误差计算模型;在此基础上设计出一种基于双NURBS参数混合插补算法的五轴联动数控系统交叉耦合控制器,并对其进行仿真,仿真结果表明,使用该交叉耦合控制器能有效提高五轴联动数控系统的零件加工精度。     

伺服运动控制轮廓误差补偿技术研究

针对单轴的定位精度问题提出了迭代学习控制方法来减小跟踪误差,并在传统PID-CCC控制器的基础上提出了模糊自适应算法在线自动调整交叉耦合的PID参数。实验证明将该方法应用于轮廓误差补偿,能够提高两轴的协调性能,可以快速地跟踪轮廓参考轨迹,不但很大程度上减小了系统跟踪误差与轮廓误差,还提高了控制系统的鲁棒性。     

X-C直驱平台平面曲线轮廓磨削廓形误差非线性耦合控制

为提高X-C平台的曲线轮廓加工精度,引入了双轴联动耦合控制思想。根据切点跟踪加工原理,提出X,C轴跟踪误差耦合形成廓形误差的计算模型,在此基础上设计了X-C直驱加工耦合控制系统。为削弱曲线轮廓X-C磨削过程中轮廓轨迹、加工速度变化、磨削力变化、控制参数等因素对轮廓精度的影响,研究非线性PID调节的控制策略来补偿控制X,C轴跟踪误差引起的廓形误差。建立了直线电机与力矩电机构成的X-C直驱加工平台仿真模型,并以凸轮加工为例进行非线性交叉耦合廓形误差补偿控制仿真实验。结果表明:与常规加工相比,所设计的非线性交叉耦合控制器能够在一定程度上提高X-C直驱平台曲线轮廓的加工精度。     

参数自调整交叉耦合的轮廓补偿关键技术的研究

针对许多CNC两轴联动存在进给负载扰动、机械系统延迟、轮廓误差协调增益控制环的参数不匹配等问题,通过参数自调整就可以达到交叉耦合的轮廓补偿的目的,进而可以提高CNC加工精度。采用CNC机床参数自调整交叉耦合的轮廓补偿方法,调整p进行交叉耦合变增益控制,设计变增益交叉耦合增量C,抑制曲线多轴交叉耦合轮廓控制,使用MATLAB进行仿真。仿真结果表明:采用CNC机床参数自调整交叉耦合的轮廓补偿,可以最大可能地消除了交叉耦合的轮廓,使得自调整交叉耦合的轮廓补偿显著性的提高,该方法有效地提高轮廓精度,满足高速、高精度的插补误差补偿。     

面向伺服动态特性匹配的轮廓误差补偿控制研究

在多轴数控加工中,轮廓误差直接决定零件最终加工精度。交差耦合控制和任务坐标系法通过估计轮廓误差,并设计轮廓跟踪控制器来提高轮廓精度。这两种方法存在大曲率位置轮廓误差估计精度差,轮廓控制增益整定依赖于工程经验等问题。为此,从伺服轴动态特性匹配出发,提出了一种基于轮廓误差精确计算的轮廓误差补偿控制方法。根据足点定义,采用解析方法快速准确计算轮廓误差。将轮廓误差分量分别补偿到各伺服轴的速度环和转矩环,提高各伺服轴动态特性的匹配程度。采用两维和三维NURBS曲线开展轮廓跟踪试验。试验结果表明:所提出的轮廓误差计算方法可以精确求解轮廓误差;所提出的轮廓误差补偿控制方法不需要建立轮廓误差与伺服跟踪误差间的映射关系,且可通过调整控制器增益定量显著减小轮廓误差。     

基于齿隙的新型圆弧独立轮廓误差交叉耦合控制

在高精密轮廓加工中,线性轮廓误差控制精度是非常重要的指标,它决定了最终产品的加工精度。在建立基于齿隙的线性轮廓误差模型的基础上,利用众所周知的交叉耦合控制,提出了一种新的独立轮廓误差控制(Independent Contour Error Control,ICEC)策略,即驱动轴之间不需要任何交叉进给信号就能够减少线性轮廓误差。仿真的结果表明所提出的控制方案是有效的,在线性和圆形轮廓的双轴驱动系统上也得到证明,能够明显地提高轮廓误差控制精度。     

Robust iterative learning contouring controller with disturbance observer for machine tool feed drives

In feed drive systems, particularly machine tools, a contour error is more significant than the individual axial tracking errors from the view point of enhancing precision in manufacturing and production systems. The contour error must be within the permissible tolerance of given products. In machining complex or sharp-corner products, large contour errors occur mainly owing to discontinuous trajectories and the existence of nonlinear uncertainties. Therefore, it is indispensable to design robust controllers that can enhance the tracking ability of feed drive systems. In this study, an iterative learning contouring controller consisting of a classical Proportional-Derivative (PD) controller and disturbance observer is proposed. The proposed controller was evaluated experimentally by using a typical sharp-corner trajectory, and its performance was compared with that of conventional controllers. The results revealed that the maximum contour error can be reduced by about 37% on average.     

Precision tracking control of a horizontal arm coordinate measuring machine in the presence of dynamic flexibilities

One of the major sources that affect measurement accuracy and limit the use of high motion speeds in coordinate measuring machines (CMM) is the position error. In fact, static and dynamic probe errors are more direct factors in measuring machine accuracy, but are not the subject of this research. However the accuracy of acquisition of component position errors using a CMM in motion is also of importance, hence the dynamics of a CMM need to be considered. Therefore, this research aims to model the dynamics of a horizontal arm CMM by considering drive flexibility at joints and evaluates the characteristics of the system for fine motion control purposes. Design of a precision tracking controller (PTC) to perform superior tracking for enhancing the measurement accuracy and the probing speed in providing less inspection time at high motion speeds is carried out. A dynamic model for the CMM is developed including drive flexibilities represented with lumped springs at the joints. Due to the non-collocated nature of the control scheme in the flexible CMM dynamics, a non-minimum phase system is observed in the proposed CMM model. Using the derived CMM model with joint flexibilities, tracking motion control simulations are conducted at different probing speeds for the cases where a PI controller and a feedback PTC are employed. A comparison of the PI controller with the feedback PTC is also performed. Results demonstrate that the effects of joint flexibilities on the contour error and probing speeds are significant and the PI controller is not capable of providing good accuracy during challenging tasks such as corner tracking. However, the simulation results indicated that by using the proposed feedback precision tracking controller, contour errors in corner tracking that are caused by joint flexibilities can be reduced effectively .     

Milling contour error control using multilevel fuzzy controller

Machining contour error plays important roles in product quality. This paper presents an implementation of multilevel fuzzy controller in controlling contour errors while maintaining the desired feed rate of milling processes. The orthogonal global task frame was used to transform the tool positions from the Cartesian coordinate system to the curvilinear coordinate system. Contour error and tracking lag error calculated from the curvilinear coordinate system were used by the multilevel fuzzy controller to drive the machining axis on the Mazak VQC-15/40 vertical machining center. The contour error of the machined work piece measured by the coordinate measuring machine showed that the contour error were significantly reduced and the feed rate were regulated at the desired speed.     

优化840D数控系统参数实现机床的高精度加工

以使用西门子840D数控系统、611D驱动装置的机床为例,通过调试机床参数,改善提高伺服系统动态响应,减小轮廓误差,提高加工精度,达到驱动与机械传动间的最佳匹配.     

Contouring controller design for biaxial feed drive systems considering compliance of transmission mechanism

Contouring control is an effective method for computer numerical controlled machining, and various such designs have been proposed to date. However, the compliance of the transmission mechanism is not considered in most existent contouring controller designs. This paper presents a new contouring control system design considering the compliance of a transmission mechanism based on a fourth-order model of feed drive dynamics. First, we present a controller design that enables the controller gain assignment for reducing the error component orthogonal to the desired contour curve, independent of the tangential error component. Although this design provides better control performance with small control input variance, there exists an inherent contour error because of the difficulty in calculating the exact contour error for any contour curve in real time. To address this problem, a reference adjustment method is used to estimate the actual contour error. The effectiveness of the proposed design is experimentally verified by comparing the control performance with a design based on a plant model that neglects the compliance.     

Adaptive nonlinear contour coupling control for a machine tool system

The quality of products from a machine tool system is largely determined by the tolerances maintained, which is a function of how well the desired contour is tracked. To mitigate contour errors in a three-axis machine tool feed drive system, the control development in this paper is based on an error system that is transformed into tangential, normal, and binormal components to the desired contour (i.e., a cross-coupling controller (CCC)). Unlike previous CCCs, the controller developed in this paper does not assume exact knowledge of the inertia and friction matrices. Specifically, an adaptive estimate is developed to compensate for uncertain friction and inertial parameters. Lyapunov-based methods are used to craft the adaptive estimate and to prove global asymptotic contour tracking. Experimental results of the proposed controller on the x–y-axes of the high speed milling machine showed improvement of the contouring accuracy compared to proportional-derivative controller and a benchmark CCC.