Wall thickness error prediction and compensation in end milling of thin-plate parts

End milling has been widely adopted to machine the thin-plate parts that play increasingly important role in the aerospace industry, due to the advantages of high machining accuracy and fine machined surface quality. In this paper, a systematic method is proposed to predict and compensate the wall thickness errors in end milling of thin-plate parts. The errors are caused by the static deflections induced by the varying cutting force imposed on the weakly rigid part. To improve the efficiency of computing the part deformation, a novel FE model is firstly developed by combing the methods of substructure analysis, special mesh generation and structural static stiffness modification. Then, the time- and position-dependent deformations of the part are calculated based on the proposed FE model to predict the wall thickness errors left on the finished part. It reveals for the first time that the surface topography of the finished thin-plate part is formed by the repeated cutting with the bottom edge of the cutter (BEC) in end milling. Owing to the coupling between the axial cutting depth (ACD) and the force-induced deflection, the modified ACDs for compensation of the static wall thickness errors are finally determined by an iterative adjustment method. The proposed method is verified by three-axis end milling experiments. The experiment results show that the predicted wall thickness errors match well with the really measured ones, and the errors are reduced by 77.18% with the help of the proposed compensation method. Moreover, the proposed FE model reduces the computational time elapsed for error prediction by 67.44% as compared with the benchmark FE model.     

Thermal error modelling for real-time error compensation

A modelling strategy for the prediction of both the scalar and the position-dependent thermal error components is presented. Two types of empirical modelling method based on the multiple regression analysis (MRA) and the artificial neural network (ANN) have been proposed for the real-time prediction of thermal errors with multiple temperature measurements. Both approaches have a systematic and computerised algorithm to search automatically for the nonlinear and interaction terms between different temperature variables. The experimental results on a machining centre show that both the MRA and the ANN can accurately predict the time-variant thermal error components under different spindle speeds and temperature fields. The accuracy of a horizontal machining centre can be improved through experiment by a factor of ten and the errors of a cut aluminium workpiece owing to thermal distortion have been reduced from 92.4 µm to 7.2 µm in the lateral direction. The depth difference due to the spindle thermal growth has been reduced from 196 µm to 8 µm.     

采用间隙误差补偿与螺距误差补偿改善机床最终数控精度

采用间隙误差补偿与螺距误差补偿的方法,改善机床最终数控精度并介绍了具体应用过程。     

数控机床几何误差的综合建模与补偿

对数控机床进行误差补偿是提高数控机床加工精度的有效方法.而建立快速准确的误差模型又是实施误差补偿的前提和基础.以三轴数控机床为对象,建立综合误差模型.     

Thermal displacement error compensation in temperature domain

Thermal displacement errors are becoming more and more important in the precision engineering field where the specifications are ever increasing. This paper proposes a novel technique to compensate in-plane thermal displacement errors in a thin plate under a moving disturbance heat load. The displacement error is evaluated at the point of the moving heat load. The technique utilizes Thermal Modal Analysis (TMA) as a means to analyze the transient temperature distribution in the plate and estimate the thermal displacement field resulting from that temperature field. The temperature field is controlled by applying additional heat loads to the plate to control and eliminate some of the modes in the temperature domain which have the largest influence to the thermal displacement error. The theory of thermal modal analysis and the developed technique of controlling modes in the temperature domain are explained. The experimental setup and results are shown to validate the control of the thermal modes.     

Angle error compensation in wheel force transducer

Wheel force transducers (WFTs) have performance characteristics that make them attractive for applications in endurance evaluation of road vehicles, ride and handling optimization, tire development and vehicle dynamics. Since the WFT is mounted on the wheel and rotates with it, the rotational angle of the wheel is indispensable to calculate the real wheel forces. Unfortunately, an angle error caused by the steering of the vehicle will be incorporated into the measurement of the rotational angle, resulting in great error in the wheel force calculation. A new compensation algorithm is proposed in this paper to eliminate this angle error. In this algorithm, the GPS speed has been introduced to modify the measurement of the rotational angle in real time. Simulations with designed vehicle movement are carried out to demonstrate the effectiveness of the compensation algorithm. Furthermore, the results of real vehicle test show that this algorithm can be successfully used in practice to get more reasonable wheel loads.     

影响待测物面测量误差的因素及补偿

分析被测物面对激光三角法测量技术的影响,从原理、位移传感器的非线性补偿、被测表面倾角、被测表面特征(颜色、粗糙度、光泽)几方面分析误差产生的原因。探讨各因素的误差补偿方法,对传感器进行非线性误差标定,测量出其非线性误差曲线图;使用标注件标定激光头本身倾角误差,对绘制倾角误差测量结果做曲线拟合;对被测件表面的颜色处理;在非特定条件下,可以忽略表面光泽度和粗糙度;最后综合上述过程,得出测量结果。该方法提高了测量精度。对于小型机电,电子产品外形反求测量,提高其生产过程中的测量精度,具有一定指导作用。     

微小型航姿测量系统设计及误差补偿

航姿测量系统在通用航空、无人机、智能机器人等领域有着广泛的应用。设计了一种基于MEMS(micro electronic mechanical system)陀螺、加速度计、磁场计的微小型航姿测量系统,利用磁场强度和加速度计信息作为观测量,提出了基于Kalman滤波器及专家系统的航姿估计算法,该算法可根据加速度及磁场信息调整滤波器的量测噪声矩阵,使系统同时满足静态及动态的使用要求。分析了影响航姿精度的主要误差及相应的误差补偿方法,包括器件零偏、刻度系数误差、温度漂移及磁场干扰等。将系统输出与高精度惯导系统对比,该系统在静态下的姿态测量精度优于0.2°,动态条件下优于0.6°,满足设计要求。     

Eccentric error and compensation in rotationally symmetric laser triangulation

Rotationally symmetric triangulation （RST） sensor has more flexibility and less uncertainty limits because of the abaxial rotationally symmetric optical system. But if the incident laser is eccentric, the symmetry of the image will descend, and it will result in the eccentric error especially when some part of the imaged ring is blocked. The model of rotationally symmetric triangulation that meets the Schimpflug condition is presented in this paper. The error from eccentric incident laser is analysed. It is pointed out that the eccentric error is composed of two parts, one is a cosine in circumference and proportional to the eccentric departure factor, and the other is a much smaller quadric factor of the departure. When the ring is complete, the first error factor is zero because it is integrated in whole ring, but if some part of the ring is blocked, the first factor will be the main error. Simulation verifies the result of the analysis. At last, a compensation method to the error when some part of the ring is lost is presented based on neural network. The results of experiment show that the compensation will make the absolute maximum error descend to half, and the standard deviation of error descends to 1/3.     

内圆磨床电磁无心夹具定位误差分析

轴承环磨削过程中,以轴承环外径作为定位基准,在电磁无心夹具上磨削轴承环外滚道。通过分析轴承环外径表面圆度误差对轴承环外滚道的影响,改进了轴承右内圆磨床电磁无心夹具上的加工方法,降低了轴承环外径定位表面圆度误差对轴承环外滚道的影响,提高产品质量,达到了降低废品损失的目地。     

激光跟踪仪测角误差补偿

由于激光跟踪仪的角度测量精度直接影响仪器的测量精度,本文提出了用自准直仪结合多面棱体对跟踪仪金属圆光栅测角误差进行离散标定的方法。研究了基于谐波分析的误差补偿方法,取金属柱面圆光栅测角误差中幅值较大且相位基本不变的谐波分量建立了补偿模型,避免了最小二乘法不收敛的问题。分析了标定测角误差的不确定度,结果显示：水平测角精度补偿前后分别为1.60"和0.90",俯仰测角精度补偿前后分别为4.89"和0.91",精度分别提高了44%和81%,从角秒级提高到了亚角秒级。结果表明,提出的方法可为激光跟踪仪水平和俯仰轴系提供测角误差补偿,对类似测角系统的误差补偿也有参考价值。     

三坐标数控机床误差建模与补偿的实验研究

以多体系统运动学分析理论为基础,利用双频激光干涉仪测量机床误差,采用九线法辨识机床误差参数,结合具体机床,准确建立了误差补偿的数学模型,利用已发开的误差补偿软件实现了误差补偿,显著地提高了数控机床的加工精度.     

加工精度在线检测系统预行程误差预测与补偿

预行程误差的预测和补偿能够大大提高加工精度在线检测系统的测量精度.提出了一种基于BP神经网络的检测误差预测新方法,建立了一个基于BP神经网络的在线检测系统预行程误差预测模型,通过实验数据对该网络进行训练,并将训练好的神经网络应用到实际加工零件的误差预测和补偿.为了验证该方法的有效性,以一圆柱零件的圆度误差检测为例,对其加工精度的在线测量进行了预行程误差的预测与补偿,经与CMM检测结果的对比,说明了该方法的有效性.     

定位误差的尺寸链解法探讨

这里阐述了运用尺寸链原理计算定位误差的方法，给出了计算步骤，并通过实例说明了如何分析、计算定位误差。     

精密机床几何误差补偿技术及应用

误差补偿技术是提高精密机床精度的有效途径,本文研究了影响精密机床精度的主要因素,重点分析了几何运动误差及热误差源的检测、建模和实时补偿技术。     

Adaptive compensation for eccentric error in truck scale

The conventional compensation for eccentric error in truck scale is realized by repeatedly regulating the potentiometer in junction box to adjust gain of each channel with load cell, which is fussy and labor-intensive. In this paper, eccentric error sources are analyzed, and an error model is established. A method of adaptive compensation for eccentric error is proposed, and its model of compensation based on radial basis function neural network (RBFNN) is established, which considers the output signals of multiple load cells as its input variables. A learning algorithm of RBFNN is also presented. Experiments and verifications in field show that with adaptive compensation the eccentric error from some nonlinear factors of truck scale is greatly reduced, and it is less than the maximum permissible error of scales with medium accuracy defined by international standard OIML R76 “Nonautomatic Weighing Instruments”.     

滚珠丝杠维修策略与误差补偿研究

在工程实际维修过程中,针对备件短缺的常见问题,以FANUC Oi Mate-TB的数控车床维修滚珠丝杠为研究对象,结合工厂实际采用修配法更换不同螺距、不同螺旋旋向和不同长度尺寸的滚珠丝杠,并设定了轴旋转方向、柔性齿轮比参数和采用锁紧式联结轴套加长轴的长度至满足要求.采用XL-80型激光干涉仪检测了机床X/Z轴反向间隙、...     

机床夹具定位误差的计算机辅助数据处理

简要介绍了定位误差的研究现状,分析了定位误差的产生机理及其计算方法.以典型单基面定位方案和典型组合面定位方案构建机床夹具定位方案资源库,结合系统开发流程图,通过VB6.0工具开发定位误差计算机辅助数据处理的误差校验系统,并以实例验证了系统良好的使用性能和操作界面,进一步完善CAFD质量评价体系.     

Chord error constraint based integrated control strategy for contour error compensation

Frontiers of Mechanical Engineering - As the traditional cross-coupling control method cannot meet the requirements for tracking accuracy and contour control accuracy in large curvature positions,...     

Thermal error compensation method for machine center

High-speed machining (HSM) technology has become the most important application in metal cutting industries. However, overcome the positioning error is one of a great concern. The position error happens due to poor machine structure design and thermal expansion comes from cutting, especially when HSM is applied. In this paper, a new technique is developed to compensate for these errors. The thermal images are used to confirm dispersion of all the affect positions. PT-100 thermo-measuring sensors are applied to detect the thermal expansion. And a mathematical model is built by multi-variable regression analysis, which is based on the sensed temperature variation and the thermal expansion. Finally, these errors are reduced significantly by sending a feedback to the microprocessor. Meanwhile, the thermal deformation can be compensated by the mathematical model, under the condition when the machine is equipped with linear encoder. Moreover, based on the simulation, it is possible to reduce the number of sensors from ten to six, which save the memory capacity and great benefit for calculating and speeding the process of algorithm. The model improves the accuracy of machining which meets the precision requirement of HSM technology. As the result of various machining tests, the axial positioning error can be reduced from 20 μm to be 3 μm, which is a significantly improvement than existing methods.