基于定位基准消除过定位的方法

过定位是不正确的定位,在工件加工中会产生严重的后果。在确定定位方案时,要采取一些措施来消除过定位。传统阐述的消除过定位方法缺少具体的规则,导致难以解决一些疑难定位问题。本文提出基于定位基准消除过定位的方法,具有理性和规律性,为生产实际、教学、计算机辅助夹具设计提供一种具体、简单易行的方法。     

定位基准的选择

在加工图1所示工件的A、B尺寸时,我们原来用90°锥面定位。其缺点是定位面小,定位不稳,而且装夹劳动强度大。现在采用端面定位,新设计的夹具见图2。     

定位基准的判断及定位误差的计算

计算定位误差时,首先要确定加工时的定位基准,判断基准是否重合,定位基准的确定,直接关系到定位误差的计算方法,依此提出了一种确定定位基准的方法及定位误差的计算方法,此方法更具有实用性、合理性。     

机械加工定位基准的探讨

在用专用夹具加工机械零件时,经常遇到粗基准的选择问题,而多数中小企业的夹具设计人员往往只从六点定位原则考虑,对粗基准的选择时,较少考虑零件毛坯的实际成形方式。现以我公司生产的一零件为例,对零件机械加工定位基准进行进一步的探讨。     

浅析机加工工件定位基准的正确选择

工件在机床上或者夹具中时,用作确定位置的基准称为定位基准,定位基准分粗基准和精基准.定位基准的合理选择直接影响着机械加工的质量与稳定性.     

转向节加工定位基准改进

正汽车底盘系统零件大多数具有不规则的结构特征,如转向节产品就是加工部位空间方位多,孔系间的位置度要求高,各部位间有较为复杂的空间尺寸链关系的异形零件。常用转向节毛坯为铸件或锻件状态,其加工工艺无论采用分散方式还是集中方式,都需要根据不规则的毛坯外形选择合理的定位方式,才能保证定位的稳定性和加工产品的一致性。笔者根据多年转向节的加工经验及不同方式的尝试,对汽车转向节在金属加工中的定位方式进行了分析。     

圆盘类旋转零件定位基准的选择

柴油机的飞轮，中小发电机的风扇等，形状类似圆盘，在机器中绕轴或同轴一起作旋转运动。装配前，这些零件要单独或和部件一起进行机械平衡。合理地选择定位基准，对保证加工精度和零件的质量分布均匀都有决定性的影响。在加工中使零件质量分布比较均匀，这样便可以较多的...     

工件定位基准的定义及其确定新探

分析了工件轮廓要素和中心要素之间的关系，提出了应统一以直接与定位元件的定位表面接触的工件上的轮廓要素为定位基准的观点。     

A mathematical approach to analysis and optimal design of a fixture locating scheme

In manufacturing engineering, localization accuracy is a key concern in the design of a fixture to specify a locating scheme and tolerance allocation. This paper presents a general analysis methodology that is able to characterize the effects of localization source errors based on the position and orientation of the workpiece. From this methodology, a fixture model is formulated by taking into account the overall errors among the system consisting of the workpiece and the fixture in the design of the fixture locating scheme. With this model, the locating principle and a criterion of the robust optimal design are then proposed to improve the localization quality of the fixture. Some examples are provided and allow for a detailed discussion about how to carry out the optimal design of the locating scheme. A comparative study is also made between the optimal solution and the empirical one. Finally, an experiment is made to validate the fixture locating scheme for a cylindrical workpiece. We conclude that this robust design method effectively achieves stable machining precision in workpieces.     

Automatic datum dimensioning for plastic injection mould design and manufacturing

Datum dimensioning (or ordinate dimensioning) technique is very popular in plastic injection mould drawings where the location dimensions of a large number of hole features must be specified in the drawings of the mould plates. Although commercial CAD/CAM systems provide semi-automatic tools to assist the designer in the dimensioning process, it is still a very tedious process, as the user has to specify the location of each dimension tag. This paper reports a completely automatic method where optimal placements of the dimension tags can be determined. The method employs dynamic programming technique to optimize the dimension process with respect to several criteria that can be selected by the user. The method has been implemented and incorporated into a commercial CAD/CAM system, and examples are given to illustrate the important features of the program.     

新一代天气雷达资料整编软件的研制与开发

为便于对新一代天气雷达灾害性天气过程个例资料进行整编,利用VC编写程序,主要解决雷达基数据读取、记录时间格式转换和按规定格式进行文件更名。本文介绍软件的设计思路、软件功能和程序开发技巧。     

基于多色集合理论的定位基准选择推理技术

为解决计算机辅助工艺设计中定位基准选择问题,提出了定位基准推理过程的形式化方法,分析工件定位中各种知识的约束关系.首次应用多色集合理论的个人颜色、统一颜色和递阶结构树,建立了工件定位基准递阶结构信息模型.以三平面定位方式为例,确定第一、第二和第三定位基准围道矩阵.建立了启发式定位基准选择顺序,按照工件定位基准围道矩阵确定的标准,以箱体类零件为例,验证了所提方法的有效性.     

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.     

浅论凸轮测量任选基准的选择方法

证明了“敏感点”是凸轮测量的最佳任选基准；介绍了在数显式凸轮测量仪上以“敏感点”为基准确定凸轮测量位置，即测量起始转角的求解过程。     

安全防范自动化系统设计研究

通过对某水电公司调度大楼的楼宇智能化集成系统的设计，对安全防范自动化系统做了系统的介绍，并提出了需要注意的问题。     

Information fusion based optimal control for large civil aircraft system

Wind disturbance has a great influence on landing security of Large Civil Aircraft. Through simulation research and engineering experience, it can be found that PID control is not good enough to solve the problem of restraining the wind disturbance. This paper focuses on anti-wind attitude control for Large Civil Aircraft in landing phase. In order to improve the riding comfort and the flight security, an information fusion based optimal control strategy is presented to restrain the wind in landing phase for maintaining attitudes and airspeed. Data of Boeing707 is used to establish a nonlinear mode with total variables of Large Civil Aircraft, and then two linear models are obtained which are divided into longitudinal and lateral equations. Based on engineering experience, the longitudinal channel adopts PID control and C^⁎ inner control to keep longitudinal attitude constant, and applies autothrottle system for keeping airspeed constant, while an information fusion based optimal regulator in the lateral control channel is designed to achieve lateral attitude holding. According to information fusion estimation, by fusing hard constraint information of system dynamic equations and the soft constraint information of performance index function, optimal estimation of the control sequence is derived. Based on this, an information fusion state regulator is deduced for discrete time linear system with disturbance. The simulation results of nonlinear model of aircraft indicate that the information fusion optimal control is better than traditional PID control, LQR control and LQR control with integral action, in anti-wind disturbance performance in the landing phase.     

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。