BP神经网络补偿并联机器人定位误差

为减小机构末端定位误差,提高机器人运动精度,分析了所开发的6-DOF精密并联机器人末端位姿的误差来源及以往误差补偿方法的局限性。通过实际测量末端位姿,在精密定位的局部工作空间内,提出了基于BP神经网络的机器人关节空间误差补偿方法。确定了BP神经网络模型,建立了误差补偿的数据样本,并对数据样本进行了标准化,通过实验对比的方法确定了隐层神经元的个数,同时对网络的推广能力进行了验证。经过误差补偿,6-DOF精密并联机器人的平移定位误差下降了80%,转角定位误差下降了60%。该实验结果表明,基于BP神经网络的误差补偿方法对机器人局部工作空间的补偿具有明显的效果,满足精密并联机器人工作的精度要求。     

新型6自由度并联机器人误差补偿

分析了新型6自由度并联机器人的位置误差和姿态误差。在误差概率分析与蒙特卡洛法的基础上,建立铰链间隙影响下的机器人实际误差模型。并在直接误差补偿法和工作空间补偿的基础上,结合并联机器人平台模型及误差模型提出一种适合该模型的误差补偿方法。该方法具有一定的普遍性。     

An accurate probe pre-travel error compensation model for five-axis on-machine inspection system

On a five-axis CNC machine tool, the pretravel errors of touch-trigger probes are severely affected by gravity and must be compensated to ensure the required measurement accuracy. The situation is more complex than that of the three-axis on-machine inspection system. This paper proposes a simple and accurate modeling and compensation method for the probe pretravel error of a five-axis on-machine inspection system. First, the pretravel error for the 5-axis CNC tool is decoupled into three parts, which are analyzed based on the probe's mechanical structure. Then, a new calibration point selection strategy is proposed to obtain the accurate reference sphere center. Finally, we carry out calibration tests to validate the proposed method. The compensation results show that the proposed compensation method for the probe pretravel error under the influence of gravity (PPEUG) can improve the accuracy considerably.     

2TPR&2TPS 并联机构的位姿误差建模与补偿研究

位姿精度是评价机器人性能好坏的一个重要指标,建立有效的补偿算法是提高机器人位姿精度的重要保证。 本文以 一种 2TPR&2TPS 并联机器人为研究对象,建立了基于正解的误差模型,根据该误差模型得出了动、静平台位置参数误差及 驱动杆零点长度误差与机器人末端位姿误差的关系,同时建立了基于逆解的补偿算法。 通过粒子群算法对误差函数的最小 值寻优,得到了机器人驱动杆补偿量和位姿补偿量,仿真得出该机器人的平均位置精度提升了 98. 148% ;将驱动杆补偿量与 理想位姿对应的驱动杆长叠加作为机器人的驱动杆输入量进行实验验证,实验得出机器人的平均位置精度提升了 87. 457% ,补偿效果显著。     

立式加工中心空间几何误差辨识解析及定位误差补偿研究

为大幅提升立式加工中心加工精度,满足当代数控机床对高精度的需求,针对立式加工中心3个运动轴,深入分析了其轴向运动空间几何误差,提出了可有效辨识运动轴轴向运动空间6项几何误差的辨识方法.建立了空间6项几何误差辨识模型,并针对关联轴联动垂直度误差进行了有效分析,建立了垂直度误差辨识解析模型.同时,针对3个独立运动轴轴向定位...     

An integrated error compensation method based on on-machine measurement for thin web parts machining

Thin webs are widely used in the aerospace industry for the advantages of compact structure, light weight and high strength-to-weight ratio. Due to its low rigidity, serious machining error may occur, therefore, Finite Element method and mechanism analysis are usually utilized to modeling its deformation. However, they are very time-consuming and only suitable for elastic deformation error. In this study, an integrated error compensation method is proposed based on on-machine measurement (OMM) inspection and error compensation. The OMM inspection is firstly applied to measure the comprehensive machining errors. The Hampel filtering is then used to eliminate outliers, followed by the triangulation-based cubic interpolation as well as a machine learning algorithm which are used to establish the compensation model. At last, the real time compensation of high-density cutting points is realized by developing the compensation system based on External Machine Zero Point Shift (EMZPS) function of machine tool. Three sets of machining experiment of a typical thin web part are conducted to validate the feasibility and efficiency of the proposed method. Experiment results revealed that after compensation, the comprehensive machining errors were controlled under different machining conditions and 58.1%, 68.4% and 62.6% of the machining error ranges were decreased, respectively. This method demonstrates immense potential for further applications in efficiency and accuracy improvement of thin-walled surface parts.     

新型并联机器人坐标测量机误差建模与仿真

介绍了一种新型五自由度并联机器人坐标测量机机构,该测量机机构具有五个驱动分支和一个约束分支,可以实现三维移动和二维转动。为了给该坐标测量机实际误差的补偿和控制奠定理论基础,提高测量精度,改善测量性能,根据其位置反解数学模型,导出了测头位姿误差与各运动副位置误差、调节器运动误差及测头长度误差之间的相互关系,建立了该测量机的误差模型,并通过计算机仿真对误差模型的正确性进行了验证。     

新型6-PSS并联机器人的位姿误差分析

在获得6-PSS并联机构位置反解的基础上,考虑杆长、铰链位置、铰链间隙等各类主要误差源对终端误差的影响,推导出此新型机构的位姿误差模型,且应用蒙特卡洛技术分析了位姿误差的分布规律,为这种机器人的理论设计与精度补偿提供了理论基础。     

基于五轴机床的叶轮实体建模与加工

由于整体叶轮的叶片是扭曲的,在建模和加工方面都有极大的困难。相比三轴加工机床,五轴机床具有较高的生产率和较好的加工质量等优点。根据实际工程数据,选用Pro/Engineer软件对实体叶轮进行造型,并对整体叶轮数控加工的走刀路径进行了分析和研究,针对干涉问题,选取刀轴自动避让功能,并定义刀轴限界功能。成功将NC程序从Powermill软件中导入到DEMAGE五轴机床。并以某离心式压缩机整体叶轮产品为例进行了加工验证,加工出了实体产品。实验结果表明选用的加工方法和工艺是非常成功的。     

平面并联机器中变值几何参数的误差补偿方法

针对平面并联机器运动学标定无法补偿的变值几何参数误差,提出一种标定后误差的线性预估实时补偿方法。该方法提前由测量仪器测量出部分机器终端误差修正值,在机器运行时,数控程序将实时调用这些误差修正值,并预先由直线插值线性计算出机器终端所到位置的误差修正值,并将这些计算出的误差修正值提前补偿到位置目标指令中,从而达到提高精度的目的。该方法简洁高效、工程实用性强,可广泛适用于少自由度并联机器。     

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.     

五轴数控机床旋转轴几何误差测量与建模

利用球杆仪对五轴数控机床旋转轴的几何误差进行了测量及建模。在测试中,五轴数控机床采用两个平动轴和一个旋转轴同步运动,球杆仪采用径向、切向和轴向三种测试路径,并在此基础上对其进行几何误差建模。     

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.     

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.     

三轴激光陀螺温度误差动态建模及补偿技术

提出了一种新的三轴激光陀螺温度误差动态建模及测试方案,并进行了实验。实验结果表明,新的动态模型能够对大变温率、大范围温变条件下陀螺的漂移进行有效补偿,且补偿后陀螺精度在全温度范围内优于0.05 °/h 。与静态模型相比,动态建模方法具有测试时间短、模型精度高及易于工程实现等优点。     

基于D-H矩阵的3-RSR并联机器人的误差建模

本文通过选取3-RSR并联机器人的任意一条支链作为研究对象,利用D—H矩阵建立动平台相对于静平台的位姿关系矩阵,采用矩阵微分法推导出机构原始误差到末端执行部分的误差映射模型。该模型包含了机构全部的几何原始误差,同时将末端执行部分位姿误差与原始几何误差间的非线性隐式函数关系简化为线性显式函数关系,是进一步研究误差补偿的基础。     

并联加工中民加工数据处理

由于并联加工中心的制造误差、并联加工中心主轴和动平台间存在的不垂直度误差,会使零件加工表面形成阶梯;此外由于一般CAM软件形成五坐标加工程序时,不能对拐点处进行减速和变姿态,容易引起叶片加工在拐点处过切。因此,研究主轴和动平台间不垂直度误差测量和补偿方法,和判断加工程序拐点和对拐点速度进行处理的方法,用以解决这两个问题。     

Local interference detection and avoidance in five-axis NC machining of sculptured surfaces

The tool interference problem is the most critical problem faced in sculptured surface machining. This paper presents a methodology for interference detection and avoidance in five-axis NC machining of sculptured surfaces with a filleted-end cutter. The surfaces to be machined are divided into convex and non-convex regions. There is no local interference inside the convex regions. For the non-convex regions, based on the analysis of the different local interference, local gouging is first detected and avoided by determining optimal cutter orientations. Rear gouging detection and avoidance algorithms are then proposed for simple smooth surfaces and complex shaped surfaces, respectively. The techniques presented in this paper can be used to generate interference-free tool paths. The realistic results indicate that the proposed method is feasible and reliable .     

A new high-efficiency error compensation system for CNC multi-axis machine tools

To enhance the accuracy of CNC machines for the request of modern industry, an effective static/quasi-static error compensation system composed of an element-free interpolation algorithm based on the Galerkin method for error prediction, a recursive software compensation procedure, and an NC-code converting software, is developed. Through automatically analyzing the machining path, the new error prediction method takes into consideration the fact that the machine structure is non-rigid, and can efficiently determine the position errors of the cutter for compensation without computing a complex error model on-line. The predicted errors are then compensated based on a recursive compensation algorithm. Finally, a compensated NC program will be automatically generated by the NC-code converting software for the precision machining process. Because of the advantage of the element-free theory, the error prediction method can flexibly and irregularly distribute nodal points for accurate error prediction for a machine with complex error distribution characteristics throughout the workspace. To verify the algorithm and the developed system, cutting experiments were conducted in this study, and the results have shown the success of the proposed error compensation system.     

Evaluation of the power consumption of a high-speed parallel robot

An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. Afterward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low-power-consumption workspace is selected for the robot.