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.     

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     

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 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:

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.     

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℃。     

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.     

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.     

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.     

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。     

Embedded CMAC learning controller for scan-tracking measurement in copying manufacture: results of a case study

Surface scan-tracking measurement is one of the key technologies in copying manufacture. In conventional scan-tracking measuring processes of irregular surface, the model surface geometric shape and the friction between the probe and model surface are two main factors that can seriously affect the measuring accuracy and efficiency. In order to reduce the impact of these factors and improve measurement efficiency while maintaining measurement accuracy, this paper presents a novel embedded cerebellar modular articulation controller (CMAC) learning controller for scan-tracking measurement in copying manufacture. New approaches to model surface features (including geometric feature and friction feature) identification and quantification are given specifically. Conventional scan-tracking control law is improved by taking into account the impact of model surface feature, and it is combined with CMAC neural network so that it can automatically predict the surface features and adjust the scan-tracking velocity in advance. Thus, high measuring efficiency can be obtained by accelerating scan speed in smooth areas of model surface and decelerating prior to scanning the surface feature cusp regions. Working with a commercial open CNC system, the design steps, integration process, and results of applying the embedded CMAC learning controller were described in detail through the examples of real measurement. Actual industrial tests show a higher measurement efficiency which demonstrates the effectiveness of proposed control strategy for scan-tracking measurement.     

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。     

A robust nonlinear stabilizer as a controller for improving transient stability in micro-grids

This paper proposes a parametric-Lyapunov approach to the design of a stabilizer aimed at improving the transient stability of micro-grids (MGs). This strategy is applied to electronically-interfaced distributed resources (EI-DRs) operating with a unified control configuration applicable to all operational modes (i.e. grid-connected mode, islanded mode, and mode transitions). The proposed approach employs a simple structure compared with other nonlinear controllers, allowing ready implementation of the stabilizer. A new parametric-Lyapunov function is proposed rendering the proposed stabilizer more effective in damping system transition transients. The robustness of the proposed stabilizer is also verified based on both time-domain simulations and mathematical proofs, and an ultimate bound has been derived for the frequency transition transients. The proposed stabilizer operates by deploying solely local information and there are no needs for communication links. The deteriorating effects of the primary resource delays on the transient stability are also treated analytically. Finally, the effectiveness of the proposed stabilizer is evaluated through time-domain simulations and compared with the recently-developed stabilizers performed on a multi-resource MG.     

Development of a new lapping method for high precision ball screw (1 report)-feasibility study of a prototyped lapping tool for automatic lapping process

Ball screws are being lapped as a finishing process to improve the travel variation, drunkenness and surface finish in order to provide high precision requirements in various mechanical applications. However, the existing manufacturing method is very labor intensive that needs a highly skilled machinist to perform the hand lapping operations using the conventional laps which have two or three slits. These types of lap cannot eliminate and improve the special components of drunkenness such as ellipsoidal, triangular and other polygonal cross sections. This paper presents a new lapping method to determine the technical and operational feasibility of a prototyped lapping tool with the combination of a flexible lap and polyurethane elastomer which can be mounted in the vertical-type automatic lapping machine. This new type lapping tool with six slits, is especially designed which each section can move in radial direction wherein the uniform lapping pressure is applied on the test piece from six directions. Based on experimental results, it showed that the travel variation was greatly reduced along with drunkenness and lapping time.     

A Study on the Influence of Waviness Error to a Hydrostatic Bearing for a Crankshaft Pin Turner

This article describes a theoretical analysis of a hydrostatic journal bearing for a crankshaft pin turner by considering the waviness error of the journal and bearing. The authors found adequate design parameters to operate the crankshaft pin turner bearing. The flow rate, radial clearance, and eccentricity were selected as the basic design parameters. The load-carrying capacity of the bearing as a function of the design parameters was studied in the case of a true circular journal and bearing. The influence of the waviness error on the load-carrying capacity was then investigated; cosine functions were selected for the waviness functions. As a result, the load-carrying capacity varied according to the amplitude and phase angle of the waviness functions. Thus, it was found that the influence of the waviness error is a significant factor in analyzing lubrication characteristics.

Run-out accuracy analysis method according to the waviness phase angles of the journal and bearing was suggested. It was found that the phase angles between the bearing load wave and load-carrying capacity wave are important factors that affect the running accuracy in addition to the amplitude of waviness error.     

A double lead stain method for enhancing contrast of ultrathin sections in electron microscopy: a modified multiple staining technique

A modification of the conventional method for the staining of ultrathin sections resulted in an increase in contrast of ultrastructural detail in tissues. Tissues embedded in Spurr's low viscosity embedding medium were stained with freshly centrifuged Reynolds' lead citrate for 1–5 min, rinsed in double distilled water and dried prior to staining with a saturated solution of uranyl acetate for 40 min, and freshly centrifuged Reynolds' lead citrate for 20 min. Sections treated by this procedure showed enhanced staining of cellular organelles and cytoplasmic matrix. This procedure is recommended for tissues with poor staining qualities resulting from either prolonged fixation or from inadequacies in the buffer or embedding medium used.