超精密平面磨削0.1μm微量进给装置的实验研究

微量进给可满足可延性磨削的要求,微量进给装置采用压电陶瓷作为控制元件,通过调节空气轴承供气压力,实现超精密平面磨削０．０１μｍ的微进给量,实验表明该装置可用于磨床导轨误差的缓进给补偿控制中。     

超精密平面磨削0.01μm微量进给装置的实验研究

微量进给可满足可延性磨削的要求,微量进给装置采用压电陶瓷作为控制元件,通过调节空气轴承供气压力,实现超精密平面磨削０．０１μｍ的微进给量,实验表明该装置可用于磨床导轨误差的缓进给补偿控制中。     

模糊自学习误差补偿方法及其在位置误差补偿中的应用

提出了一种新的模糊自学习误差补偿方法，根据伺服机构的位置误差和位置的变化率，利用模糊规则和推理得出位置误差初始校正值，采用自学习、自校正技术生成位置误差校正表。该方法成功应用于开环数控系统的位置误差补偿。     

数控直线电机进给定位误差补偿技术研究

介绍了应用双频激光干涉仪测试数控直线电机进给的定位误差方法,并利用最小二乘法分别建立定位误差的线性模型、分段线性模型、样条拟合模型,并对数控直线电机进给的定位误差进行补偿。研究结果表明,采用软件补偿的方法可以较大地提高直线电机进给的定位精度。     

应用潜变量回归在线补偿双直接进给轴热误差

为了提高直线电机驱动的双直接进给轴的运动精度,对该类进给轴的热误差进行了建模并研究了误差补偿方法。分析了双直接进给轴进给过程中热误差产生的原因及其补偿的复杂性,给出一种基于潜变量回归的双直接进给轴热误差在线补偿方法。该方法应用激光干涉仪测量进给轴的热变形量,使用热电偶和红外测温仪测量进给轴关键点的温度变化;通过时间匹配变形和温度数据得到统计样本并建立基于潜变量回归的热误差识别模型。以模型的在线计算确定误差补偿量,给出了与数控系统兼容的补偿控制输出策略及补偿系统构建方案。在自构建的龙门双直线电机驱动进给轴平台上进行了在线补偿实验。结果表明:应用潜变量回归方法对双直接进给轴进行热误差补偿可使双直接进给轴的热误差减小75%。     

高速精密数控进给伺服系统摩擦误差的研究

针对一个实际的X—Y高速精密数控工作台，建立了一种考虑摩擦影响的PID控制下的进给伺服系统的数学模型。伺服机构中的摩擦力大小通过二维混合摩擦模型实现精确预测。通过MATLAB仿真模拟和使用球杆仪实际测量，在不同的工况下，分析了工作台做圆运动换象限时出现尖峰突起的误差现象，并因此得到了进给速度及进给半径对摩擦所造成的轮廓误差的影响曲线。     

高速、高精度数控伺服工作台摩擦误差的研究

建立了一种考虑摩擦影响的PID控制下的高速、高精度进给伺服工作台的数学模型。伺服机构中的摩擦力是采用一种“两维混合摩擦模型”来描述的。该模型可以根据滑动速度、表面接触物体的油膜厚度等计算摩擦力。通过数值仿真与实际测量 ,在大范围的工况下 ,研究了圆运动过象限时出现凸起的误差现象。通过计算与试验结果的比较 ,证明了提出的考虑摩擦影响的数学模型能够精确地模拟PID控制下的高速、高精度进给伺服工作台的动力学过程 ,能够正确地预测进给运动过程中摩擦误差大小及特征。     

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。     

基于车削加工工件测量的误差补偿技术

提出两种基于车削工件测量的误差补偿方法 ,即误差反向叠加的微进给补偿法与逆变刀具路线的软件补偿法 ,介绍这两种方法的原理与实现方法     

混合KPLS与模糊逻辑的双直接进给轴全行程热误差建模及补偿

为了提高双直线电动机驱动的同步直接进给轴的运动精度,对该类直接进给轴的全行程热误差在线补偿方法进行了研究。分析了双直接进给轴全行程热误差的影响因素,提出一种基于核偏最小二乘法(Kernel partial least squares,KPLS)和模糊逻辑相结合的双直接进给轴全行程热误差的在线补偿方法。应用激光干涉仪测量其热变形量,使用热电偶和红外测温仪测量进给机构关键点的温度,以时间匹配温度和变形量数据建立统计样本,在均匀离散点位置建立热误差KPLS识别模型,通过在线计算得到离散点热误差补偿量,再根据任意位置与离散点的模糊关联程度,综合计算全行程任意位置处热误差补偿量。以此理论为基础,建立补偿决策函数和补偿系统,依据补偿决策函数智能推断补偿值,通过向数控系统发送补偿码实现在线补偿。在自构建的龙门双直线电动机驱动的直接进给轴平台上,进行全行程热误差在线补偿试验研究,结果表明:混合KPLS与模糊逻辑可以有效的对双直接进给轴全行程热误差在线补偿,经过随机测试验证,补偿后的进给精度提高了50%。     

线性不确定性电液位置伺服系统的前馈补偿滑模鲁棒跟踪控制研究

针对线性不确定性系统的鲁棒跟踪控制问题,提出了一种前馈补偿滑模鲁棒跟踪控制方法,并证明了采用该方法所构成的闭环系统是李亚普诺夫意义下渐近稳定的,将该控制器设计方法应用于某结构疲劳试验机电液位置伺服控制系统,验证了所设计控制器的有效性。仿真和实时控制结果均证明：对存在不确定性的结构疲劳试验机电液位置伺服系统,应用该研究所提出的具有前馈补偿的滑模鲁棒跟踪控制器,能较有效地削弱常规VSC所固有的抖振现象,在不同的负载条件下跟踪不同频率的正弦信号均能获得良好的跟踪精度,控制器对系统的不确定性呈现较强的鲁棒性。     

Real-time inverse hysteresis compensation of piezoelectric actuators with a modified Prandtl-Ishlinskii model

This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model.     

Sliding-mode repetitive learning control with integral sliding-mode perturbation compensation

This paper proposes a sliding-mode repetitive learning control (SMRLC) scheme with an integral sliding-mode perturbation observer (ISMPO) for repetitive tracking control tasks. The three control strategies which are synthesized to yield excellent tracking performance are: (1) the pole-placement feedback control to specify the desired error dynamics; (2) ISMPO-based feedback compensation as the robust part; and (3) a feedforward learning component that refines the control to improve system performance through repetitive trials. The ISMPO-based feedback compensation ensures that there is only small tracking error during initial learning trials and enhances system insensitivity to exceptional and aperiodic disturbances. The feedforward learning compensation is updated according to a certain switching signal that is equivalent to the compensation error of the feedforward control, yielding fast convergence of the learning process from trial to trial. Experimental results demonstrate the feasibility of the proposed scheme.     

SVD-based Preisach hysteresis identification and composite control of piezo actuators

In this paper, the singular value decomposition (SVD) based identification and compensation of the hysteretic phenomenon in piezo actuators are addressed using a Preisach model. First, this paper presents an SVD-based least squares algorithm and a revision approach of the identification through updating the SVD. With the identified parameters and a log of the memory curve, a Preisach-based inversion compensator is constructed which is complemented with a feedback controller to address the inevitable and residual modeling errors. Experimental results are furnished for both the identification and compensation approaches. The Preisach-based feedforward controller significantly improves the tracking performance and reduces the root-mean-square (RMS) tracking error of a PID controller by 76.7% and 89% at 1 Hz and 25 Hz, respectively. With the proposed composite controller, the percent-RMS errors at 1 Hz and 25 Hz are reduced to 0.035% and 0.31%, respectively.     

复合前馈补偿的超磁致伸缩执行器精密伺服控制

研究了一种内嵌超磁致伸缩执行器(GMA)的智能镗削装置,针对GMA迟滞非线性,给出了一种基于复合前馈补偿的精密伺服控制方法。简要介绍了经典Preisach迟滞数值模型的实现方法,给出了一种基于迭代的迟滞非线性补偿方法以避免直接求取Preisach逆模型。讨论了迭代算法的实现步骤,验证了算法的可行性。分析了异圆销孔的镗削加工特点,在迭代补偿的基础上设计了重复控制补偿器,并结合两种补偿方法,给出了一种基于复合前馈补偿的PID控制方法,最后通过实验检验了方法的有效性。实验结果表明:在开环情况下,所给的迭代算法可以将GMA的迟滞非线性由补偿前的-15.7%~+11.8%减小到-4.6%~+5.2%,而基于复合前馈补偿的PID控制则可将误差进一步减小到±1 μm以内。实验表明,迭代补偿算法是有效的,该算法在补偿迟滞非线性的同时可避免直接求取Preisach逆模型,而基于复合前馈补偿的PID控制方法还可进一步提高GMA的控制精度。     

STUDY ON THE FEEDFORWARD COMPENSATION OF THE MOTIONERRORS OF NC MACHINE TOOLS

ＳＴＵＤＹＯＮＴＨＥＦＥＥＤＦＯＲＷＡＲＤＣＯＭＰＥＮＳＡＴＩＯＮＯＦＴＨＥＭＯＴＩＯＮＥＲＲＯＲＳＯＦＮＣＭＡＣＨＩＮＥＴＯＯＬＳＹｕＷｅｎｈｕａ；ＷｕＺｈａｏｔｏｎｇ（ＺｈｅｊｉａｎｇＵｎｉｖｅｒｓｉｔｙ）ＡｂｓｔｒａｃｔＡｆｅｅｄｆｏｒｗａｒｄ...     

Feedforward coefficient identification and nonlinear composite feedback control with applications to 3-DOF planar motor

Due to modeling errors, accurate feedforward coefficient of the controller cannot be obtained with the standard method on the basis of the nominal model. Meanwhile, the system is uncertain in practice. Consequently, the MIMO (multi-input multi-output) system of the planar motor cannot be completely decoupled by feedback linearization, and the convergence of the tracking errors is no longer guaranteed. In order to improve the robustness and the tracking ability of the planar motor, a feedforward coefficient identification method and nonlinear composite feedback controller are proposed, thus guaranteeing stability by Lyapunov theory, wherein the feedforward coefficient can be obtained by the PD control experiment. The results of two different trajectory tracking experiments show that it is more accurate than the standard method. Moreover, this coefficient is suitable for different trajectories, so it avoids the drawback of ILC (iterative learning control) method, by which the feedforward term obtained cannot be reused if the length of the trajectory changes. The nonlinear composite feedback controller consists of u ₁ and u ₂ terms. u ₁ is designed to compensate for modeling errors, therefore the robustness is improved and the coupling effects among multi-DOF (degrees of freedom) are reduced. In balancing the trade-off between disturbance rejection and noise sensitivity, an amplitude-based variable-gain function is applied in u ₂. The trajectory tracking experimental results show that the overall controller is an attractive approach for the uncertain multi-DOF systems.     

液压容积调速系统静态前馈补偿仿真研究

虽然容积调速方法是一项传统内容,但在大力提倡节能环保的今天,由于它的节能特质,应该重新得到重视。基于泵变量调节或马达变量调节的液压容积调速系统,如果采用基于给定值的静态前馈补偿,可以很方便地确定前馈补偿控制律,进而实现静态前馈-反馈复合控制,针对不同的使用场合和控制要求,可以调整前馈和反馈控制器的权重,以获得最佳效果。采用这种控制方法,对于融合了变量泵调速和变量马达调速的宽范围液压容积调速系统,进行AMESim建模和仿真分析。结果表明,这一方法比常规PID方法具有更好的阶跃响应性能和正弦曲线跟踪性能。     

压电微动工作台的位移复合控制

为解决稳态精度和稳定性之间的矛盾,提高压电陶瓷执行器的控制性能,进而提高其驱动的微动工作台的定位精度,构造了一种前馈补偿同反馈调节相结合的复合控制算法。其中,前馈补偿为基于压电陶瓷执行器迟滞非线性模型的前馈控制,通过自学习算法来实现,用来补偿压电陶瓷执行器的迟滞非线性,提高对参考位移信号的跟踪能力;反馈调节为PID反馈控制,用来进一步校正前馈补偿没有消除的偏差以及由模型的不确定性所引起的误差,且为了减小积分饱和作用以及微分对扰动的敏感性,对PID算法进行了改进,使之成为一种变系数积分与加权微分的PID算法。试验验证了该算法的有效性,并将该算法同其他控制算法——开环控制、前馈控制、PID 反馈控制进行了对比试验研究,结果表明,复合控制算法比其他控制算法具有更好的性能。     

Applications of integrated motion controllers for precise CNC machines

The error resources of precise motion control systems are basically categorized into linear and nonlinear effects. To realize the precise motion of industrial computer numerical control (CNC) machines, this paper presents an integrated motion control structure with modular algorithms, including both the linear control and the nonlinear compensation. In the linear control design, this study applies three algorithms: (1) feedforward control to address the tracking errors, (2) cross-coupled control to reduce the contouring errors, and (3) digital disturbance observer to lessen the effects of modeling errors and disturbances in real applications. The results indicate that the linear motion controller achieves greatly improved accuracy in both tracking and contouring by reducing the servo lags and mismatched dynamics of the different axes. However, the adverse effect due to friction still exists and cannot be eliminated by applying the linear motion controller only. This study further integrates the nonlinear compensator and develops friction estimation and compensation rules for CNC machines. The digital signal processors are suitable to implement all the developed linear and nonlinear algorithms, and the present controllers have been successfully applied to industrial CNC machines. Experimental results on a vertical machining center indicate that, under different feed rates, the CNC machine with the integrated motion controller significantly reduces the maximum contouring error by 135% on average.