一种提高模糊控制器稳态控制精度方法的研究

针对模糊控制器本身在消除系统稳态误差时性能比较差,通过对隶属度函数和控制精度之间关系的阐述,提出了一种简单的方法,通过对隶属度函数的调整使控制精度得到提高.仿真结果表明,该方法有较理想的性能、较高的稳态控制精度和广泛的实用性.     

A study on accuracy of porous journal air bearing

In order to predict error motion of continuous porous journal air bearing, an accuracy model is established to reveal the relationship among error motion, roundness error and structure parameter under quasi-static conditions. Based on the model, averaging coefficient is defined to quantitatively characterize the error averaging ability. The study finds that whether the bush and shaft roundness errors match is the cause of error motion. The trilobal roundness error of shaft has a major impact on accuracy for a porous journal air bearing with an elliptical bush, while the elliptical roundness error of shaft has a major impact on accuracy for that with a trilobal bush. On the two-dimensional plane of bush wave numbers n₂ = 2~7 and shaft wave numbers n₁ = 2~15, the averaging coefficients are symmetrical along the line n₁ = n₂. The shaft wave numbers which equal integer multiples of prime numbers of bush wave number have no impact on accuracy, while the remaining shaft wave numbers have impact. Among them, those at points n₁ = n₂*i ± 1 are with obvious averaging coefficients and have a major impact on accuracy where i is a positive integer. The main peaks of averaging coefficients appear at the points n₁ = n₂ ± 1, which have the most important impact on accuracy. The theory has many potential applications such as prediction of error motion, structural optimization and selection of parts grinding method, which is of significant importance for design and testing of porous journal air bearings used widely in ultra-precision machine tools.     

高炉风机故障预报系统

根据长治钢铁 (集团 )有限公司炼铁厂生产的需要 ,针对其关键生产设备六高炉风机建立了故障预报系统 ,详细阐述了预测技术的选择和预测模型的建立过程 ,成功地将灰色加一元线性回归模型应用于风机运行状态的预测 ,并编制了相应的预报程序     

一种提高SIFT特征匹配正确率的方法

针对尺度不变特征变换(SIFT)特征匹配算法存在计算量大、实时性差、误匹率高的问题,提出一种基于距离比率准则的方法来去除SIFT特征匹配中的错误匹配。传统的方法是采用随机选取一致性(RANSAC)方法选取出正确的匹配对,但是需要通过反复迭代,复杂、耗时并且仍存有部分误匹配的现象。改进后的方法直接通过两条匹配直线斜率的一致性判断,剔除不在斜率范围内的匹配,此方法算法简单,省时高效,从而较大提高了特征匹配的正确率。实验结果表明,通过采用距离比率准则方法具有较高的匹配精度,同时减少了匹配的时间,使实时性得到提高。     

A simple method of accuracy enhancement for industrial manipulators

A robot calibration method which includes identification of kinematic parameters and error compensation is presented. The parameter identification process features an easy-to-perform measurement procedure using a low-cost, instrumented, articulated linkage, and with proper planning of the data collection process, the measurement of actual end effector positions can be performed automatically. The basis of the parameter identification approach is akin to that of closed-loop mechanism synthesis. For error compensation, a computation scheme based on the nominal model as opposed to the calibrated one is presented. The resulting algorithm, allowing the exploitation of the closed-form inverse kinematics solutions available for most industrial robots, is computationally efficient and therefore suited for on-line applications. Examples based on simulation studies, devised to include realistic operating conditions, are presented to demonstrate the feasibility of this method. The effects are also investigated of the number of measurements and of the sensor resolution on the overall quality of the identification.     

试论夹具保证零件准确度的技术条件

用夹具装夹工件进行机械加工时,由于诸多原因,会使工件产生加工误差。设计夹具时,应灵活地利用“误差不等式”,合理地分配和控制各项误差的大小,使夹具可靠地保证被加工零件的精度要求。     

A new approach for oblique weir discharge coefficient prediction based on hybrid inclusive multiple model

One type of long-crested weir is oblique weir. Oblique weirs are longer than standard weirs. Therefore, they can pass more discharge capacity than weirs at the given channel width. The main objective of the present study was to investigate the efficacy of several intelligent models including multiple linear regression (MLR), Gaussian process regression (GPR), artificial neural network (ANN) and multiple models driven by ANN (MM-ANN) methods in estimating oblique weir discharge coefficient (C_d). Different input combinations were predicted using the variables of H/P, P/L_e, and W/L_e and the output coefficient of discharge. Prediction models were analyzed by statistical index, including root mean square error (RMSE), correlation coefficient (R), error percentage chart, relative error (RE%) plot, Kling-Gupta efficiency (KGE), probability density function (PDF) plot, scatter plot, scatter plot of error residuals and Taylor's diagram. Obtained results showed that the ANN model performed best by combining the inputs of the three variables (i.e., H/P, P/L_e, and W/L_e) with R = 0.746 and RMSE = 0.065 among the standalone models. Eventually, the proposed hybrid model MM-ANN was most accurate in estimating the oblique weir C_d by improving the prediction results of the implemented models.     

Comparison study on the accuracy of metamodeling technique for non-convex functions

In order to increase the efficiency of design optimization, many efforts have been made on studying the metamodel techniques for effectively representing expensive and complex models. In this study, a comparison is conducted on the accuracy of several widely used meta-model techniques — moving least squares (MLS), Kriging, support vector regression (SVR) and radial basis functions (RBF) — which are able to approximate non-convex functions well. RMSE (root mean squared error) value is identified as a measure of the accuracy for this comparison. Each metamodel technique is used to approximate the six well-known mathematical functions and a resign of experiment (DOE) is generated by using the Latin hypercube design (LHD), which is also performed for each resulting metamodel. The results show that Kriging and MLS can create a more accurate metamodel than SVR and RBF with the mathematical functions tested. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Byeong-Soo Kim received B.S and M.S. degree in Mechanical Engineering from Hanyang University in 2006 and 2008, respectively. Mr. Kim is currently a Research Engineer at LG Electronics. Yong-Bin Lee received a B.S. and M.S. degree in Mechanical Engineering from Hanyang University in 2002 and 2004, respectively. He is currently a Ph.D. student in Hanyang University. Mr. Lee’s research interests are in the area of optimization, approximation, and design of experiments. Dong-Hoon Choi received a B.S. degree in Mechanical Engineering from Seoul National University in 1975. He then went on to receive his M.S. from KAIST in 1977 and Ph. D. degree from University of Wisconsin-Madison in 1986, respectively. Dr. Choi is currently a Professor at the School of Mechanical Engineering at Hanyang University in Seoul, Korea. He is currently the director of iDOT(the center of innovative design optimization technology). Prof. Choi’s research interests are in the area of optimization techniques: developing MDO methodology, developing optimization techniques to ensure a reliability of optimum solution, and developing approximation optimization technique, etc.     

A comprehensive method for calibration of volumetric positioning accuracy of CNC-machines

A comprehensive method for measuring the systematic errors of CNC-machine tools has been studied. The method used for measurement and calibration of machine tool errors should be general and efficient. The objectives of this study include:

The development of a multi-turn absolute encoder—a new concept in accordance with a design insensitive to accuracy

A new design concept of a multi-turn absolute rotary encoder which is insensitive to the accuracy of encoder components is proposed. This new design does not demand high accuracy of the encoder structure other than the fundamental pattern to produce the least significant digit. The allowable error in the encoder structure is compensated by electronic light circuits. This absolute encoder has been applied to the measurement of height position in a cylindrical form-measuring system. The new encoders can be connected in series by reduction gears whose accuracy is fairly rough, so that a multi-turn device in realized. The allowable tolerances in the encoder structure are presented.     

渗金属气压对光电高温计测温精度影响的实验研究

为准确控制双辉等离子渗金属工件的温度,借助自制的一套热电偶测温实验装置,对光电高温计测温进行了比对实验,探讨了气压对光电高温计测温精度的影响。实验结果表明:在双辉等离子渗金属过程中,对同一工件温度,随工作气压的升高,光电高温计所用的ε值也增大。工作气压每增高5～10Pa,将ε值提高0 1,这时光电高温计的温度测量误差会小于±3℃。     

空间失稳目标线阵激光成像建模及参数优化

线阵激光成像雷达兼具激光测距和线阵成像的优点,是空间失稳目标远距离精密测量的重要工具,其获取的线阵图像既能用于运动估计也能用于空间目标三维测量。为模拟不同平面分辨率线阵激光成像雷达对空间失稳目标的数据采集,本文根据线阵激光成像雷达的成像机制及空间失稳目标的运动规律提出了一般性的空间失稳目标线阵激光成像建模方法,为不同地面验证方案提供了数据支持。同时,为优化雷达参数选取,本文通过计算单位区域特征获取率提出了一种基于数据采集完整性评估的线阵激光成像雷达参数优化方法,实验分析了与成像分辨率相关的性能参数对多种运动形式空间失稳目标数据采集的完整性。实验结果显示数据采集完整性与线阵规模及采样频率正相关,在线阵规模达到100元以上、采样频率200Hz以上,与空间目标自身运动形式几乎无关,建立的对应关系将为参数优化提供指导和参考依据。     

加工过程质量仿真

首先提出了一种在并行工程环境下用于小批量生产的质量反馈两层模型,能够准确、客观、在线动态地评价现行加工工序的状况和进行相应的加工过程质量仿真,以便对新零件的公差带设计提供指导。接着针对多批次小批量问题,提出了一种抑制数据中系统噪声和观测噪声的方法,可以有效地提高建模的精度。然后利用多组实验数据对提出的模型进行研究,充分地说明了以上方法的有效性和实用性。最后,针对广东省惠阳机械厂生产的ＺＪＴ－４０型全自动胶囊充填机的充填杆外圆磨削加工过程,运用提出的多批次数据建模方法,有效地弥补了因小批量数据所固有的信息不完整性而无法精确建模的缺陷。     

A study of the durability of flexible magnetic media in a linear tape system

Travan™ linear tape drives (with the head removed) and custom-made tape cyclers were used for sample generation in a preliminary study of the durability of experimental particulate media. The first tester cycled short (1 m) closed loops of tape, whereas the second cycled cartridge loaded media for an identical number of passes (0, 100, 250, 500, 1000, 5000, 10 000). X-ray photoelectron spectroscopy was used to identify chemical changes to the media surface and in the case of the Travan tester, these changes were compared to dropout growth through the use of a dedicated Travan drive. The results show binder depletion and an increase in surface lubricant with increasing number of cycles, irrespective of the type of tester used. The tapes exhibited good durability since the surface changes did not have a detrimental effect on the dropout characteristics.     

一种相控阵天线安装精度检测与校准

文中论述了一种相控阵雷达天线安装后的精度检测方法。按照雷达天线安装后的几何形态,采用光学测量仪器进行相关的数据采集,建立检测的数学模型,利用线性回归法以及最小二乘法进行数据拟合,计算出安装后雷达天线底面与水平面的最大夹角和天线边缘与正北方向的夹角,并进行了试验误差评估和分析,依据检测数据对雷达天线的水平和方位角度进行校...     

A method for improving the accuracy of evaluating the dimensions of flaws in walls of tubular elements of structures

An algorithm for evaluating the real accuracy of the basic measuring instrument (exterior or in-tube flaw detector) in measuring parameters of flaws of a particular inspected tube was proposed on condition that the basic measuring equipment has no systematic error, while a verification instrument is considered as “absolutely” precise or “reference.” A statistical method of increasing the accuracy of evaluating the dimensions of flaws in thin-walled tube elements was developed on the basis of a correlation between the dimensions of flaw parameters. It can be taken as a basis for finding real values of parameters of flaws and for performing reliable calculations of the residual strength and residual life, for scheduling optimal periods for the next inspection of pipelines, and for ranging segments of a pipeline by a risk criterion, thus providing optimal scheduling of repairs.     

A basic theoretical study of the temperature rise in sliding contact with multiple contacts

The objectives of this paper are to develop a theoretical solution for the temperature rise due to sliding contact between surfaces with multiple, interacting asperities and to use this solution to examine the effects of the important contact area and system parameters. A solution based on the Green's function method is developed for the basic problem of two half-space regions in sliding contact with any arbitrarily specified arrangement of rectangular asperities.Studies are conducted to demonstrate the effects of the contact area parameters, namely the number, size, spacing and orientation of the contacts, as well as sliding velocity. Results indicate that the contact temperatures are extremely sensitive to the number and relative spacing between contacts, where subdivision of a single contact into separated pieces significantly reduces the contact temperature rises. The orientation of the contacts relative to the sliding direction is shown to have only a small influence on temperature. The shape of the contacts also has only a small influence, except in the case of contact patches with large aspect ratios where significantly lower surface temperatures can occur. Sliding speed is shown to be extremely important in that increased speed causes both higher temperature levels and greater interaction between contacts due to the convective effect.The current paper is intended to describe the basic solution methodology for calculating temperature rises due to multiple, interacting contacts and to show some fundamental trends for a selected set of regularly arranged contact area distributions.     

XH718加工中心的热误差补偿研究

在分析某XH718加工中心主轴及主轴箱结构和热源的基础上,在主轴箱上初步选择多个测温点,根据测温点温度和主轴热误差的数据,应用模糊聚类分析和相关性分析对测温点进行了优化,确定最小数量的关键测温点。然后应用多元线性回归理论建立了关键测温点的温升和热误差的数学模型。数学模型在加工中心上补偿后的数据表明,可以在很大程度上改进加工中心的精度,达到了客户需要的精度要求。     

A framework for failure recovery in a manufacturing cell

The maturity level of an automated manufacturing system can be measured by the failure-recovery capability of the system. This paper addresses the unique characteristics of failure-recovery problems in manufacturing cells, suggests a framework to cope with the problems, and presents a recovery strategy. Opportunistic and incremental problem-solving concepts of a blackboard architecture are adopted for building the framework. A case-based strategy has been developed, which uses both heuristic knowledge and historical information to resolve the cause of failures in diverse situations. An example of tool breakage is presented which illustrates the concepts of the above-mentioned framework and strategy. Prototype software has been implemented in the object-oriented language Smalltalk-80 for this purpose.     

凿岩机器人轨迹跟踪自适应预测控制

将一种输入输出增量式线性时变模型作为对象的实时预测模型 ,采用加权限定记忆回归法来估计模型参数 ,进而提出一种自适应预测控制策略 ,并给出了单步预测最优控制律。简要介绍了凿岩机器人双三角钻臂的结构和运动特性 ,随后将本文提出的自适应预测控制策略用于双三角钻臂轨迹跟踪控制 ,仿真结果表明了该控制策略的可行性。