High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are su ciently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.

Motion Error Compensation of Multi-legged Walking Robots

Existing errors in the structure and kinematic parameters of multi-legged walking robots,the motion trajectory of robot will diverge from the ideal sports requirements in movement.Since the existing error compensation is usually used for control compensation of manipulator arm,the error compensation of multi-legged robots has seldom been explored.In order to reduce the kinematic error of robots,a motion error compensation method based on the feedforward for multi-legged mobile robots is proposed to improve motion precision of a mobile robot.The locus error of a robot body is measured,when robot moves along a given track.Error of driven joint variables is obtained by error calculation model in terms of the locus error of robot body.Error value is used to compensate driven joint variables and modify control model of robot,which can drive the robots following control model modified.The model of the relation between robot＇s locus errors and kinematic variables errors is set up to achieve the kinematic error compensation.On the basis of the inverse kinematics of a multi-legged walking robot,the relation between error of the motion trajectory and driven joint variables of robots is discussed.Moreover,the equation set is obtained,which expresses relation among error of driven joint variables,structure parameters and error of robot＇s locus.Take MiniQuad as an example,when the robot MiniQuad moves following beeline tread,motion error compensation is studied.The actual locus errors of the robot body are measured before and after compensation in the test.According to the test,variations of the actual coordinate value of the robot centroid in x-direction and z-direction are reduced more than one time.The kinematic errors of robot body are reduced effectively by the use of the motion error compensation method based on the feedforward.

MOTION ERROR ESTIMATION OF 5-AXIS MACHINING CENTER USING DBB METHOD

In order to estimate the motion errors of 5-axis machine center, the double ball bar （DBB） method is adopted to realize the diagnosis procedure. The motion error sources of rotary axes in 5-axis machining center comprise of the alignment error of rotary axes and the angular error due to various factors, e.g. the inclination of rotary axes. From sensitive viewpoints, each motion error is possible to have a particular sensitive direction in which deviation of DBB error trace arises from only some specific error sources. The model of the DBB error trace is established according to the spatial geometry theory. Accordingly, the sensitive direction of each motion error source is made clear through numerical simulation, which is used as the reference patterns for rotational error estimation. The estimation method is proposed to easily estimate the motion error sources of rotary axes in quantitative manner. To verify the proposed DBB method for rotational error estimation, the experimental tests are carried out on a 5-axis machining center M-400 （MORISEIKI）. The effect of the mismatch of the DBB is also studied to guarantee the estimation accuracy. From the experimental data, it is noted that the proposed estimation method for 5-axis machining center is feasible and effective.

Error Modeling and Sensitivity Analysis of a Parallel Robot with SCARA(Selective Compliance Assembly Robot Arm) Motions

Parallel robots with SCARA（selective compliance assembly robot arm） motions are utilized widely in the field of high speed pick-and-place manipulation. Error modeling for these robots generally simplifies the parallelogram structures included by the robots as a link. As the established error model fails to reflect the error feature of the parallelogram structures, the effect of accuracy design and kinematic calibration based on the error model come to be undermined. An error modeling methodology is proposed to establish an error model of parallel robots with parallelogram structures. The error model can embody the geometric errors of all joints, including the joints of parallelogram structures. Thus it can contain more exhaustively the factors that reduce the accuracy of the robot. Based on the error model and some sensitivity indices defined in the sense of statistics, sensitivity analysis is carried out. Accordingly, some atlases are depicted to express each geometric error’s influence on the moving platform’s pose errors. From these atlases, the geometric errors that have greater impact on the accuracy of the moving platform are identified, and some sensitive areas where the pose errors of the moving platform are extremely sensitive to the geometric errors are also figured out. By taking into account the error factors which are generally neglected in all existing modeling methods, the proposed modeling method can thoroughly disclose the process of error transmission and enhance the efficacy of accuracy design and calibration.

DEFINITION OF ERROR MOTION OF ROTATIONAL SPINDLE AND SEPARATION OF MANDREL ECCENTRICITY AND TILT

After the Machine Tool Research Institute of Czechoslovakia (VUOSO) started to measure the rotational error motion of machine tool spindle by the end of the 1950s, great efforts have been made by various scholars in China and in the United States, Japan, the United Kingdom, Russia, FRG, Switzerland, Belgium and India to acquire the most common method for measuring angular and radial error motion of spindle.

Error Analysis of Radial Motion Measurement of Ultra-Precision Spindle

This paper gives an error analysis of radial motion measurement of ultra-precision spindle including nonlinearity error of capacitive displacement probes, misalignment error of probes, eccentric error of artifact ball and error induced by different error separating methods. Firstly, nonlinearity of a capacitive displacement probe targeting a spherical surface is investigated through experiment and the phenomena of fake displacement induced by lateral offset of the probe relative to an artifact ball?are?discussed. It is shown that the error motion in radial and axial direction and eccentric rotation of artifact ball will both induce lateral offset which causes a fake output of probes. Moreover, measurement error induced by angular positioning error for three famous error separating methods is detailed.

High Accuracy On-line Measurement Method of Motion Error on Machine Tools Straight-going Parts

Harmonic suppression, non-periodic and non-closing in straightness profile error that will bring about harmonic component distortion in measurement result are analyzed. The countermeasure-a novel accurate two-probe method in time domain is put forward to measure straight-going component motion error in machine tools based on the frequency domain 3-point method after symmetrical continuation of probes' primitive signal. Both straight-going component motion error in machine tools and the profile error in workpiece that is manufactured on this machine can be measured at the same time. The information is available to diagnose the fault origin of machine tools. The analysis result is proved to be correct by the experiment.

Research on Contour Error Based on CNC Multi-axis Motion Control System

The contour error was analyzed based on CNC multi-axis motion control, the contour error model was obtained focused on beeline and different radius of curvature and common contour of curve, for a CNC biaxial motion control system and the mechanism of producing contour error and the relationship between tracking error and contour error were presented. The theoretical and practical significance of modeling error and controlling error in motion control systems was carried out.

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

A feedforward compensation naethod of the motion errors of NC machine tools imple- mented with software is proposed , with which the motion errors can be compensated whithout changing the original computer control systems of the NC machine tools. The experimental results show that the circular interpolation profile machining errors decrease by a factor of 2/3 after com- pensated.

摆线轮工作齿廓的二次分段修形方法

针对常规修形方法存在计算复杂、齿廓曲线形状控制不够灵活等问题,提出了一种摆线轮工作齿廓的二次分段修形方法。通过摆线轮齿廓压力角变化规律的分析,将工作齿廓最小压力角的位置作为二次分段修形的基准点,建立二次分段修形模型。利用直线法简单函数,推导出二次分段修形方法下各齿段修形量的计算公式及齿廓方程。采用轮齿接触分析的方法,研究了二次分段修形齿廓的传动误差和回差,并进行对比实验验证摆线轮工作齿廓二次分段修形方法的正确性和可行性。结果表明:二次分段修形的摆线轮工作齿廓与理论齿廓曲线更加吻合,传动误差和回程误差分别减少约14%和19%。

五轴数控机床旋转轴综合误差测量与辨识

针对五轴数控机床旋转轴的运动误差和几何误差的综合评估问题,在不考虑直线轴运动误差影响的情况下,提出了一种采用R-test测量仪的测量及其辨识方法。首先,测量过程按照参考球的两种不同高度设置进行,仅移动旋转轴,而不移动直线轴。其次,利用R-test测量仪对旋转轴的运动精度进行了测量。此外,假设旋转轴位置几何误差和工作台上参考球的设置误差是影响测量结果的因素,并通过最小二乘法对这些因素进行分离。采用IBS公司的R-test测量仪,对米克朗公司UCP800Duro立式五轴加工中心C轴的运动误差和几何误差进行了测量实验。研究结果表明,该方法能够正确识别旋转轴的运动误差和几何误差,可以有效地综合评估旋转轴的运动精度,并有助于进一步提高旋转工作台的精度。

基于谱压缩的大斜视TOPS BP图像自聚焦算法

在机动平台大斜视TOPS模式SAR成像时,通过使用地平面直角坐标系BP成像算法,能够在短时间内获取地距平面无畸变的宽幅SAR图像,但实际应用中如何对BP图像快速完成运动误差补偿与旁瓣抑制仍是一个难点。针对此问题,提出了一种改进的谱压缩方法,基于此能够快速实现机动平台大斜视TOPS模式地平面BP图像自聚焦等后续操作。首先,考虑到传统BP谱压缩方法仅适用于聚束成像模式,结合大斜视TOPS SAR虚拟旋转中心理论与波数谱分析,推导出了改进的精确谱压缩函数,能够通过全孔径压缩获得无模糊的地平面TOPS模式BP图像频谱。在此基础上,利用相位梯度自聚焦(PGA)能够快速完成全孔径运动误差估计与补偿。此外,基于提出的改进谱压缩方法得到的无模糊对齐BP图像频谱,可以在方位频域统一加窗实现图像旁瓣抑制。最后,通过仿真数据处理验证了所提算法的有效性。

气浮垫的误差均化能力研究

为探究小孔节流气浮轴承的误差均化能力的主要影响因素,建立单个气浮垫的误差运动模型,并利用所定义的均化系数研究气浮垫误差运动、导轨条形状误差和气浮垫结构参数三者之间的定量关系。研究表明:对于长波长的导轨条形状误差(波数为0~1),当波数逐渐增加时,均化系数从1逐渐降低到接近0;对于短波长的导轨条形状误差(波数为1~10),当波数靠近或者等于正整数时,均化系数取接近于0的最小值;当波数靠近或者等于正整数加0.5时,均化系数取小于0.25的局部最大值;结构参数中,封气边宽度对误差均化能力有很大影响,气垫间隙和小孔节流器孔径对误差均化能力基本无影响;当移动速度小于10 000 mm/s时,移动速度对误差均化能力的影响微弱。

转台运动误差分离与角度优化技术研究

为了解决测量转台运动误差时存在的多种误差耦合问题,提出了一种基于多点法的运动误差分离方法。首先,通过分析转台在回转过程中多自由度误差的运动特性,提出了一种端面四点误差分离方法,在分离出测量盘下表面的平面度误差的同时,可完成倾斜误差和轴向误差的解耦。然后,建立了该方法的误差传递函数,采用麻雀算法(SSA)进行优化,寻找不同阶次下受谐波抑制影响最小的最优布置角,提高了误差解耦精度。最后,通过仿真与实验的方式对该方法进行验证。仿真结果表明,端面四点误差分离方法对轴向、倾斜误差的分离精度(相对误差)分别为1.934%和9.177%。实验结果表明,分离的运动误差与转台标定误差相符合,验证了该方法能够精确获得转台运动误差。

基于栅格节距中心峰值检测的扫描探针显微镜校准方法

为了解决扫描探针显微镜(Scanning Probe Microscope,SPM)现有校准方法复杂程度高且存在局限性的问题,提出了一种基于二维标准微尺度正交栅格的SPM校准方法,通过对扫描获取的栅格图像进行互相关/卷积(Cross-correlation/Convolution,CC)滤波,实现对栅距中心坐标的峰值检测。校准的运动几何误差包括x轴和y轴位置偏差Δ_(x)和Δ_(y)、沿x轴和y轴扫描的直线度偏差δy和δx以及两轴之间的正交性偏差γ_(xy)。根据x轴和y轴扫描像素数、扫描范围、标准栅格计量检定节距平均值、栅距平均值计算得出校准因子C_(x)和C_(y)。采用标称节距为10μm的正交栅格样板对原子力显微镜(Atomic Force Microscope,AFM)进行校准实验,结果显示C_(x)和C_(y)分别为0.925和1.050,γ_(xy)为0.015°,该台AFM的校准扩展不确定度为0.33μm(k=2.56)。研究成果对于推动SPM校准标准文件的具体实施和执行具有积极意义,并为SPM仪器研制及性能评估提供了技术参考。

基于运动约束的航姿系统误差自主补偿方法

为了提高车载捷联航姿系统的长航时定姿精度,提出利用载车的运动约束条件对航姿系统误差进行在线自主补偿。首先,对航姿系统的传感器误差、安装误差等进行分析与建模,选取航姿系统的各项误差作为误差补偿滤波的系统状态,建立系统状态方程。然后,根据发射车等特种车辆的运动特点,利用车辆运动约束条件,将载车行驶过程中航姿系统的速度输出在车体坐标系横向和垂向上的投影分量作为误差补偿滤波的量测,推导获得误差补偿滤波的量测方程。最后,采用卡尔曼滤波设计航姿系统误差在线估计算法。实验结果表明,所提方法能够自主有效地补偿航姿系统的积累误差,经过1200 s的跑车实验,系统的航姿误差始终保持有效收敛,其中航向精度优于3.4′,水平姿态精度优于0.4′。

基于长时跟踪的滑雪教学姿态辅助矫正方法

在滑雪教学过程中,由于学员的迅速移动和姿态的大幅变化,导致以短时智能图像变化特征为主的姿态跟踪算法失效或不稳定,特别是在雪地条件恶劣或光线不足等复杂环境下,跟踪效果会受到较大的影响。为此,提出基于长时跟踪的滑雪教学姿态辅助矫正方法。使用递归最小二乘法(RLS)分类器训练得到学员姿态位置核相关滤波器(KCF)。计算最大的KCF响应值,精确检测学员的姿态位置。如果KCF结果低于经验阈值,表明目标丢失,启动再检测模块。利用光流法在前一帧学员姿态位置附近寻找当前帧中的姿态位置,以获取一个大致位置。在此位置重新应用跟踪器,获得精确的学员姿态位置,实现长时跟踪。依据得到的姿态位置数据,构建滑雪学员姿态误差补偿模型,提取学员身体的运动参数和姿态误差。通过计算身体运动参数,并结合KCF构建滑雪学员身体姿态辅助矫正模型,从而完成滑雪教学的姿态辅助矫正。实验结果表明,该方法在长时跟踪中展现出高度的有效性、可靠性和稳定性,其平均PCK指标达到92.3%,同时在目标跟踪效率上,参数量和计算量分别为30.24 MB和9.26 GFLOPs,速度达到142帧/s,实现了高效实时的跟踪,验证了该方法在滑雪教学姿态辅助矫正中的可行性。

基于运动预测的Motion JPEG2000误码掩饰新算法

Motion JPEG2000(MJPEG2000)作为新兴的视频压缩标准,鲁棒传输控制是一个重要的应用需求,而误码掩饰技术是提高其鲁棒性的有效途径之一。充分利用压缩码流冗余信息,本文提出了一种基于运动预测的Motion JPEG2000视频传输误码掩饰新算法。首先利用相邻帧及帧内子带间的相关性进行小波域内的运动估计,以低频子带内码块的运动矢量来预测高频子带内丢失码块的运动矢量,再通过运动匹配修复丢失的码块。而低频子带内数据块的丢失可通过整个高频子带图像完成运动估计,得到预测信息对低频子带系数实施误码掩饰。仿真实验结果表明,提出的算法不管在低频还是高频子带进行误码掩饰修复,均能得到较好的图像帧重建效果。

高动态姿态测量圆锥误差补偿算法改进及实时性分析

弹丸圆锥运动会对制导系统产生严重的控制干扰,为了补偿该误差,分析了一种新的圆锥误差补偿算法,以提高弹载姿态控制系统在高动态运动环境下的解算精度和实时性。结合四元数四阶龙格-库塔法和三子样等效旋转矢量法,利用修正型罗德里格斯参数改进基于角增量输出的三子样四元数姿态算法,推导相应的微分方程表达式,建立三子样四元数改进算法姿态求解数学模型。仿真结果表明,与传统圆锥误差补偿算法相比,改进算法能更有效的补偿圆锥误差,平均解算精度提高了约17.32%,减少了高动态环境下的计算量,实时性提升了约22.54%。

基于改进RRT算法的移动机械臂运动规划

为解决移动机械臂存在停靠误差和运动规划效率较低的问题,提出了一种基于改进快速扩展随机树(RRT)算法的移动机械臂运动规划方法。首先对移动平台停靠误差进行分析,通过变换矩阵进行误差补偿。然后对RRT算法进行改进,通过基于概率的目标偏置策略减少无用搜索,通过回归过滤机制避免局部重复搜索,通过自适应步长策略加快搜索速度。实验表明该改进RRT算法规划效率高且规划路径代价小,有良好的综合性能。