三自由度砂带磨床的设计与分析

介绍了一种用于复杂空间曲面磨削加工的新型机器人柔性磨削系统,重点对系统中三自由度砂带磨床的三自由度转位机构、砂带跑偏调整机构和砂带张紧机构进行了设计和分析,对砂带磨床的控制系统也做了介绍.     

A simulation platform for optimal selection of robotic belt grinding system parameters

Robotic belt grinding is an effective process for removing material from geometrically complex workpieces. However, due to the relatively low stiffness of the system, the grinding quality is prone to inaccuracies caused by system dynamics. In order to control the quality of the grinding process, a profound understanding of the system is required. This paper presents a platform for comprehensive modeling and simulation of the robotic belt grinding system. The system kinematics model is based on the CAD model of the workpiece in composition with robot kinematics. The dynamics model is a comprehensive combination of the dynamics of the robot, the grinder, and the interaction between the grinder and the workpiece. A material removal model of the grinding process, which can adapt to workpieces with complicated shapes, is also developed and presented. The system simulation shows that optimal selection of key control parameters of the grinder and proper selection of robot control strategies can efficiently suppress chatter in the grinding process. Furthermore, having the ability to predict material removal rate, the comprehensive simulation platform is also demonstrated to be a strong tool in selecting the grinding process key parameters, namely, robotic velocity and contact force, for the control of material removal to meet dimensional accuracy requirements on workpieces.     

船用螺旋桨叶片砂带磨削加工自动编程技术研究

介绍了自由曲面数控加工编程技术的国内外研究现状。根据船用螺旋桨叶片砂带磨削的加工特点,将螺旋桨叶片砂带磨削加工自动编程系统划分为五个功能模块,研究了砂带磨削加工刀具轨迹的生成过程。     

六联动叶片砂带磨削编程系统的开发研究

以VC++为编程语言和UG/OPEN API为开发工具,通过对砂带磨削运动分析、磨削刀位轨迹计算和数控代码生成等关键技术研究,最终开发了一套六轴联动汽轮机叶片数控砂带磨床编程原型系统,并采用数控加工仿真软件VERICUT构建了六轴虚拟砂带磨削环境,对编程系统生成的数控代码进行叶片型面磨削仿真,验证了系统生成的磨削刀位点以及数控代码的正确性.     

通过压电式传感器阵列测量简支梁的声辐射模态

采用一组PVDF(polyvinylidence fluioride)阵列测量了简支梁声辐射模态,在简支梁表面粘贴一组相同形状的矩形PVDF薄膜作为传感器,通过设计这组PVDF输出的加权系数,得到各阶声辐射模态的幅值。研究表明,PVDF的加权系数与辐射体表面上的外激励力无关;实验结果表明,这种声辐射模态传感器的设计是可行的。     

面向复杂曲面的机器人砂带磨抛路径规划及后处理研究

针对机器人砂带磨抛复杂曲面叶片问题,对叶片内外型面和进排气边的磨抛路径规划及后处理技术进行了研究,对复杂曲面叶片的机器人砂带磨抛路径规划的计算效率及加工效率进行了分析,提出了一种将基于等残留高度法的笛卡尔空间计算的磨抛行距转化为参数域空间的磨抛行距的方法,并将机器人砂带磨抛复杂曲面叶片接触轮的中心坐标位置、支撑轴矢量以及轴线矢量数据后处理为机器人的位姿信息,利用机器人砂带磨抛系统装备实验平台对复杂曲面叶片进行了实际的加工实验。研究结果表明:所提出的刀路规划和后处理技术能够有效地解决机器人砂带磨抛复杂曲面叶片的问题,具有加工路径总长短以及路径条数少的特点,计算简单、加工效率高、加工表面质量好。     

Capturing the tacit knowledge of the skilled operator to program tool paths and tool orientations for robot belt grinding

This paper describes a novel methodology for generating grinding tool paths, orientations and grinding parameters based on the captured trajectories of a surface finishing tool operated by the skilled operator. First, a variable frame size moving window principal component analysis is performed on the trajectories. Next, features such as the amplitude, speed of the tool centre point, direction of travel, average position, contact force and orientation of the grinder are calculated. Kernel k-means clustering is applied to the trajectory’s feature vectors for segmentation into the tool path primitives. The robotic tool path primitives would be ordered similar to the manual tool path primitives in the grinding strategy. The robotic tool path primitives are then generated based on the boundaries of the manual tool path primitive in a computer-aided manufacturing software. Anchor points are selected from the corners and at intermediate sections along the robotic tool path to inherit the orientations of the manual tool path. Using the inherited skilled operator tool orientations, spherical linear interpolation and spherical spline quaternion interpolation are used to interpolate the orientations for the robotic tool path points along the cross curves, followed by the flow curves, respectively. A finite element model of the belt grinding process is also introduced to quantify the effect of the contact wheel serrations on the material removal rate. This is to account for the difference in contact wheel design between the handheld and robotic grinding tool. The programmed robotic tool paths generated from the trajectories captured from a skilled operator were proven to be able to grind the workpiece to the desired profile within the desired tolerance in a pre-production environment.     

汽轮机叶片数控砂带磨床自动编程系统的开发研究

以VC++为编程语言,应用UG/OPEN API二次开发工具,通过对叶片实体模型分析、磨削轨迹生成、刀位点计算、磨削干涉校验和修正及后置处理等关键技术的研究,最终开发完成一套五轴联动汽轮机叶片数控砂带磨床自动编程原型系统.     

In-process endpoint detection of weld seam removal in robotic abrasive belt grinding process

This paper proposes a novel approach for in-process endpoint detection of weld seam removal during robotic abrasive belt grinding process using discrete wavelet transform (DWT) and support vector machine (SVM). A virtual sensing system is developed consisting of a force sensor, accelerometer sensor and machine learning algorithm. This work also presents the trend of the sensor signature at each stage of weld seam evolution during its removal process. The wavelet decomposition coefficient is used to represent all possible types of transients in vibration and force signals generated during grinding over weld seam. “Daubechies-4” wavelet function was used to extract features from the sensors. An experimental investigation using three different weld profile conditions resulting from the weld seam removal process using abrasive belt grinding was identified. The SVM-based classifier was employed to predict the weld state. The results demonstrate that the developed diagnostic methodology can reliably predict endpoint at which weld seam is removed in real time during compliant abrasive belt grinding.     

Real-time simulation and visualization of robotic belt grinding processes

Real time simulation and visualization are important for robot programmers to verify and optimize the path planning for the robotic belt grinding process. A new free-form surface representation based on discrete surfel element is developed to facilitate the system implementation, which exploits the advantage of the new development of point-based rendering technology in computer graphics. A local process model is integrated to calculate the material removal rate by considering the local geometry information and non-uniform force distribution. The final surface grinding error is easy to be assessed and visualized for quality evaluation. The experiments show that the simulation error is below 15%, even for a non-uniform contact under stable cutting conditions.     

大型核电叶片的螺旋磨削刀具轨迹生成

为了提高大型核电叶片的磨削加工效率和改进现有的砂带磨削刀具轨迹生成方法,提出了一种针对组合曲面叶片的六轴联动螺旋磨削方法。该方法根据组合曲面相邻边界曲线与曲面造型提出了叶片砂带螺旋磨削切触点和刀具轨迹的计算公式。基于课题组自主开发的编程系统平台编制了相应的数控编程模块,生成了连续光滑的叶片螺旋磨削加工刀具轨迹。与砂带磨削原有的横向、纵向磨削方式相比,大大减少了叶片磨削过程中的让刀时间,提高了加工效率,降低了生产成本。     

Trajectory planning for roboticbelt grinding of turbine blade

In order to improve the quality and efficiency of blade grinding, the robot and belt grinding technologies were applied to blade machining, and the characteristics and working procees of the system were introduced. Through the comparison of multi-axial machining trajectory generation technologies, equal chord deviation fitting method and equal scallop height method were adopted to plan the robot traaectory. Because of their shortcomings in blade grinding, these two methods were improved. In order to evaluate the improved methods and compare efects of manual and robotic proceesing, a test was carried out. The experimental results show that, the blade machined by robot has much beter surface quality than that by hand. The relevant experiment validates the eefectivenees of robotic machining and the improved methods. [ABSTRACT FROM AUTHOR]     

叶片机器人砂带磨抛点云匹配算法优化

为解决机器人磨抛路径中工件坐标系难以计算的问题及校正工件装夹误差,将三维点云配准技术应用到叶片机器人砂带磨抛系统中。由三维激光扫描仪扫描工件型面获得工件点云,采用基于主成分分析(PCA)的全局配准算法和改进的迭代最近点(ICP)算法完成了扫描点云和工件模型离散点云间以及不同工件扫描点云间的匹配,以获取工件坐标系和校正工件装夹误差。相关仿真和试验结果表明,优化后的算法在匹配速度与精度上有了长足改进,且加工后产品精度和质量都能满足实际加工要求。     

面向熔射快速制模的机器人自动研磨系统的开发

为解决熔射制造大中型汽车覆盖件模具过程中人工研磨时间长、劳动强度大等问题,建立了面向熔射快速制模的机器人自动研磨系统.在该系统上进行机器人研磨工艺参数实验研究,得到了研磨角度、机器人行走速度和路径对研磨表面质量的影响规律;在此基础上选择合适的研磨条件,在通过等离子熔射制造的模具表面皮膜上进行了研磨实验.实验研究结果表明,保持适当的研磨压力,选取合理的机器人行走速度、研磨角度、进给量,可得到较好的研磨效果.该机器人自动研磨系统适用于熔射制造的模具及一般模具的研磨过程.     

Analysis of the robotic disc grinding process

Two major aspects of the robotic rigid disc grinding process, namely, disc wear and grinding forces have been examined in the present study. The disc wear is observed to be nonuniform, being greatest at the outer edge of the disc. A simple wear model has been developed by assuming that the amount of wear can be approximated as having a triangular cross section. The dynamic grinding force model developed includes the effects of disc wear and nonlinear stiffness of the robot system. Experiments have been conducted on an actual robotic grinding system to verify the validity of these system models. Several practical issues which should be considered during robotic grinding are discussed.     

几器人砂带磨削系统的夹具优化

根据复杂曲面磨削任务对机器人的实际要求,提出了一种PPPRRR砂带磨削机器人构型,利用D—H法建立了机器人的运动模型及正反解方程。建立了基于该构型机器人砂带磨削系统的曲面磨削数学模型,在此基础上以高尔夫球头为典型工件代表,分析了利用夹具改变零件的装卡姿态及改变磨削机与机器人相对位置对工件可磨削性的影响,利用蒙特卡洛方法优化了磨削机与机器人的相对位置及零件装卡姿态,提高了磨削机器人系统的加工性能。     

可在线更换磨削轮的砂带磨削机床的研制

介绍了应用于机器人磨削加工系统中的可在线更换磨削轮的砂带磨削机床的结构原理。阐述了在线更换磨削轮的砂带磨削机床的磨削方式及其磨削力控制结构原理。     

Modeling and grinding large sculptured surface by robotic digitization

An efficient approach to surface remodeling and grinding tool-path generation for a large sculptured surface via robotic digitization was developed, and a prototype system was implemented to replace the manual grinding process for large marine propellers. The current manual grinding process removes cusps on the NC machined area and peels the unmachined area; the research focuses on the grinding of the unmachined area of a large marine propeller. A robotic digitization and surface remodeling methodology was developed by the use of a thickness-map that reduces a three-dimensional problem to a two-dimensional problem. Also, the local and global grinding tool-paths are generated on the reconstructed surface based on the thickness-map, and the workpiece is machined by a six-axis articulated robot. The purpose of the research is to construct a prototype system for propeller grinding experiments and further development in Hyundai Heavy Industry, Korea.     

An off-line programming system for robotic drilling in aerospace manufacturing

Off-line programming systems are essential tools for the effective use of robots in the manufacturing environment. This paper presents a dedicated off-line programming system for robotic drilling in aerospace manufacturing. Following a brief introduction of the system architecture, the paper discusses two major problems of off-line programming for robotic drilling, i.e., redundancy resolution and position correction. A new performance index is proposed for the combined requirements of singularity and joint-limit avoidance, followed by a discussion of the redundancy resolution scheme by using numerical optimization at the joint displacement level. A position correction method using measurement data of reference holes is developed for the enhancement of robotic drilling accuracy. Robot programs generated by using the developed system have been tested on a robotic drilling system, and the experimental results are provided.     

叶片复杂曲面的机器人抛磨工艺规划

为了实现复杂曲面工件的智能抛磨加工,对叶片复杂曲面进行机器人抛磨工艺规划。对抛磨点位置规划算法和基于最大接触原则的抛磨姿态规划算法进行了研究。首先,通过平行截面法获得抛磨路径割线,以非均匀有理B样条(NURBS)曲线描述。接着,提取曲线特征参数,根据设定的阈值进行抛磨点规划,再基于抛磨轮与工件的最大接触原则进行抛磨点姿态规划,从而得到完整的抛磨路径。然后,将工件位姿从工件坐标系转换到TCP坐标系。最后,搭建了柔性抛磨系统仿真平台生成机器人控制程序。实验结果表明,此方法规划的路径可用于叶片复杂曲面的机器人抛磨加工。分别用本文规划所得路径和CAM软件规划所得路径对叶片进行抛磨加工,测得表面粗糙度分别为0.695~0.930μm和2.803~3.243μm。本文提出的抛磨位姿规划方法可用于复杂曲面工件的抛磨路径规划,使工具和工件保持最大接触,从而避免了位姿不合理所产生的过抛和欠抛。