电火花线切割加工中线电极的动态特性仿真与实验研究

研究慢走丝电火花线切割加工中电极振动对加工状态的过程的影响。应用计算机仿真技术,分析连续放电力作用下线的振动模态以及对放电点转移和分布的作用。结果表明,加工工艺参数明显影响放电点的转移与分布,适当地选择工艺参数可获得最佳的放电分布率。该研究对提高慢走丝加工稳定性,防止断丝的发生提供了相应理论依据。     

滤波器表面钎焊接头钎焊钎料选择

采用软钎焊接头代替原有的螺纹连接接头用以改善 T/ R组件中滤波器上内导体与壳体的连接性能。本文在工艺实验基础上 ,通过选择合理的加热热源及钎料形式确定了满足产品质量要求的工艺方案 ,并就钎料的微量组成对性能的影响进行了分析。     

Nonlinear predictive control of a boiler-turbine unit: A state-space approach with successive on-line model linearisation and quadratic optimisation

This paper details development of a Model Predictive Control (MPC) algorithm for a boiler-turbine unit, which is a nonlinear multiple-input multiple-output process. The control objective is to follow set-point changes imposed on two state (output) variables and to satisfy constraints imposed on three inputs and one output. In order to obtain a computationally efficient control scheme, the state-space model is successively linearised on-line for the current operating point and used for prediction. In consequence, the future control policy is easily calculated from a quadratic optimisation problem. For state estimation the extended Kalman filter is used. It is demonstrated that the MPC strategy based on constant linear models does not work satisfactorily for the boiler-turbine unit whereas the discussed algorithm with on-line successive model linearisation gives practically the same trajectories as the truly nonlinear MPC controller with nonlinear optimisation repeated at each sampling instant.     

Analytical design of modified Smith predictor in a two-degrees-of-freedom control scheme for second order unstable processes with time delay

A modified form of Smith predictor is designed for controlling unstable second order plus time delay (USOPTD) processes, with/without a zero. USOPTD process transfer functions arise in modeling of many chemical and biological systems, such as isothermal continuous stirred tank reactors (CSTR) carrying out autocatalytic reactions, crystallizers and non-isothermal CSTRs. The modified Smith predictor scheme requires the design of three controllers. Synthesis method is used for the design of the three controllers, and analytical formulas are given for these controllers. The method has two tuning parameters, and guidelines are provided for selecting the tuning parameters. Robust disturbance rejection performances are achieved. Different examples are considered, and simulation studies are given, to show the effectiveness of the proposed method. A significant improvement is obtained, when compared with recently reported methods.     

Autotuning of a new PI-PD Smith predictor based on time domain specifications

The paper extends a recent work on a modified PI-PD Smith predictor, which leads to significant improvements in the control of processes with large time constants or an integrator or unstable plant transfer functions plus long dead time for reference inputs and disturbance rejections. Processes with high orders or long time delays are modeled with lower order plant transfer functions with longer time delays. The PI-PD controller is designed so that the delay-free part of the system output will follow the response of a first-order plant or second-order plant, where it is appropriate, assuming a perfect matching between the actual plant and model in both the dynamics and time delay. The provided simple tuning formulas have physically meaningful parameters. Plant model transfer functions and controller settings are identified based on exact analysis from a single relay feedback test using the peak amplitude and frequency of the process output. Examples are given to illustrate the simplicity and superiority of the proposed method compared with some existing ones.     

塑料光学元件制造

由于光学塑料具有许多杰出的优点 ,因而在照相机、光盘、投影镜头、眼镜等方面获得了日益广泛的应用。塑料光学元件的关键制造技术是模具设计和制造、选择合适的注塑设备、最佳的工艺参数等。为了制作以光盘物镜为代表的高精度非球面塑料透镜 ,就应采用注射压缩工艺抑制变形的成形技术 ,辅之以考虑变形而补偿模具的成形技术。     

Enhanced boundary lubrication by potential control during copper wire drawing

Metal deformation process, such as wire drawing, is conventionally performed under open-circuit conditions. Lubrication is heavily dependent on the surface conditions of the wire. The surface condition of the wire depends on the electrochemical reactions once the wire contacts with the emulsion lubricant. An oxide layer on the incoming wire could be removed partially or completely and repassivation occurs on the asperities of the wire after abrasion. Adsorption of fatty acid on the oxide layer of the wire could play a vital part in the efficiency of boundary lubrication. Friction could be reduced when a proper potential is applied between the wire and the auxiliary tube before the drawing dies. The reduction of friction detected at various potentials depended on the lubricant chemical composition. Surface quality could be significantly improbed and energy consumption substantially reduced by the potential control.     

高级别洁净室气流组织的优化

利用CFD方法对拟采用风机过滤器单元(FFUs)洁净空调方案的IS05级电子工业洁净室进行模拟，得出室内气流速度场，分析其性能，通过理论公式计算所能达到的洁净度。认为通过合理布置末端FFU送风口位置及选择回风形式，以及选用较高级别的末端过滤器，可以在FFU满布率较低时达到较高的洁净度级别。     

A robust decision-making methodology for evaluation and selection of simulation software package

Today, simulation has a broad range of applications from solving service problems to analyzing manufacturing problems such as warehousing and logistic systems. Simulation has become a popular methodology and selecting an appropriate simulation software package is one of the decisions that any industrial engineer may face at work. As a result, numerous types of simulation software packages have been developed for modeling simulation problems. The increasing variety of simulation software packages in the software market makes the selection of an appropriate simulation software package a critical decision. Selecting an inappropriate software package will be followed by many negative consequences. This paper will present a robust decision-making methodology based on Fuzzy Analytical Hierarchy Process (FAHP) for evaluating and selecting the appropriate simulation software package. The robust decision method aggregates the experts’ judgments for the criteria weights and the suitability of simulation software alternatives. The FAHP is used to prioritize and evaluate existing alternatives based on the proposed criteria for choosing the proper simulation software. The proposed methodology is applied to selecting the appropriate simulation software as an experiment and results are provided.     

A study on fault diagnosis and maintenance of CNC-WEDM based on binary relational analysis and expert system

The paper presents a binary relational analysis and expert system base module for maintenance and fault diagnosis of CNC wire EDM. The module proposes a framework of integrated maintenance and fault diagnosis system. The study explores the binary coded matrix system, which plays an important role in prediction and diagnosis of wire electrical discharge machining (WEDM) faults on the spot by expert guidance. In this study, 15 inputs were considered to observe eight probable causes with the help of the forward and backward propagation algorithms. Inputs and output matrices were considered in the form of a square matrix. To explain the fault diagnosis and to realize the importance of maintenance through advice, the detection of faults is investigated through forward and back propagation of matrix transformation on the spot. It is an integrated backup that can be individually focused when input and output parameter do not match. It is a time saving, knowledge acquisition, easy to maintain, and capable of self-learning system. To verify the developed framework, 120 data sets were generated for proper analyzing of acquired output through graphical representation. The paper also presents some of the important features of maintenance schedule and probable causes of wire breakage with remedial actions in tabular form. The developed system can help the operators, trainees, and manufacturing engineers in achieving trouble free machining through quick detection of faults and proper maintenance of machines in actual practice.     

A study on fault diagnosis and maintenance of CNC-WEDM based on binary relational analysis and expert system

The paper presents a binary relational analysis and expert system base module for maintenance and fault diagnosis of CNC wire EDM. The module proposes a framework of integrated maintenance and fault diagnosis system. The study explores the binary coded matrix system, which plays an important role in prediction and diagnosis of wire electrical discharge machining (WEDM) faults on the spot by expert guidance. In this study, 15 inputs were considered to observe eight probable causes with the help of the forward and backward propagation algorithms. Inputs and output matrices were considered in the form of a square matrix. To explain the fault diagnosis and to realize the importance of maintenance through advice, the detection of faults is investigated through forward and back propagation of matrix transformation on the spot. It is an integrated backup that can be individually focused when input and output parameter do not match. It is a time saving, knowledge acquisition, easy to maintain, and capable of self-learning system. To verify the developed framework, 120 data sets were generated for proper analyzing of acquired output through graphical representation. The paper also presents some of the important features of maintenance schedule and probable causes of wire breakage with remedial actions in tabular form. The developed system can help the operators, trainees, and manufacturing engineers in achieving trouble free machining through quick detection of faults and proper maintenance of machines in actual practice.     

锤柄加工精度的探讨

我校金工实习所加工的锤柄容易产生弯曲、烧伤、同轴度较差、粗糙度较大等缺陷,总结我的教学实践经验,采取了冷却,选择合理的刀具角度与切削用量,利用开口钢丝装夹工件的方法,合理有效的化解问题,提高了工件的加工质量。     

Stability analysis and dynamic regulation of multi-dimensional Taylor network controller for SISO nonlinear systems with time-varying delay

Though many studies are focused on the stabilization of nonlinear systems with time-varying delay, they fail to involve the dynamic regulation without on-line optimization commonly. For this sake, feedback linearization, Lyapunov-Razumikhin theorem and polynomial approximation theorem are employed here to verify that the multi-dimensional Taylor network (MTN) controller can stabilize the single input single output (SISO) nonlinear time-varying delay systems through dynamic regulation of the system output with no need for on-line optimization. Here, the design of the controller is transformed into a convex optimization problem, which is tackled by means of the appropriate optimization method. Like its PD-like controller peers, the MTN controller functions well in eliminating the dependence on the system model. The effectiveness of the proposed approach is demonstrated and confirmed via two examples.     

探析基于寿命成本的FMEA

FMEA(失效模态和影响分析)是一种在设计阶段预测并旨在减小危险发生概率的设计工具。通过危险优先值(RPN)来描述故障的危险度,它是发生度、严重度和检测度的乘积。FMEA虽然比较广泛地被用户使用,但是它存在一些问题:严重度和检测度非常主观且没有统一的标准;且RPN只是一个危险顺序参数,而不包含具体的改进措施。本文对这些缺陷进行研究,并提出基于成本的FMEA,一种通过寿命周期成本来度量危险度的方法。利用基于成本的FMEA对设计方案通过比较和选择,从而有效减少特定系统在使用寿命内的成本。该方法主要是通过计算检测时间、维修时间、发生度、耽误时间、中断运转时间、修复的复杂程度,用这些参数来预测使用寿命成本、标定危险度、提出改良和维护措施。     

电压互感器副边极性接线对电能表计量影响分析

文章对电压互感器副边极性接线进行分析,并通过实例进行更正系数的计算及电能表计量情况的解释,阐述了电压互感器接线正确的重要性。     

基于AutoCAD平台下开发的机床夹具设计软件

这里论述了基于AutoCAD的平台下开发的机床夹具设计应用软件,详细叙述了该夹具CAD软件的用户界面、设计功能及参数化绘图系统等,即利用该软件能完成机床夹具的构思、选型、设计、计算和绘图等工作。该计算机辅助机床夹具设计CAFD(ComputerAidedFixtureDesign)软件的应用能提高了机床夹具设计的效率及质量。     

Effect of geometrical parameters on high frequency performance of Rogowski coil for partial discharge measurements

Partial discharges (PD) in a power system component is a sever threat, indicating a high likelihood of the imminent and complete failure of the insulation. The reliability of partial discharge diagnostics depends upon the design and accuracy of the measuring sensors. In this paper the Rogowski coil is employed as a PD measuring sensor. The selection of suitable geometrical parameters has been identified as an important aspect regarding the proper operation and installation of the coil around the under test power component. These parameters significantly affect the measuring performance of the coil in terms of its sensitivity and bandwidth. The measurement performance of different geometrical designs for the high frequency Rogowski coils is evaluated. The variation in parameters such as core and coil diameter, diameter of the copper wire used for winding and number of turns, has been experimentally investigated. In addition the return winding, as a non-conventional method of creating a return loop for the Rogowski coil, is compared with a return wire (loop) to analyze sensor performance. The comparative study of variation in mechanical design features provides a brief guideline to select the optimal design of the coil.     

薄膜收卷机设计选型原则研究

给出了优质膜卷的通用定义,具体分析各种不同条件下收卷不同材质薄膜的特点和相应要求,对收卷机结构形式进行分类并提出较为完备的选用原则.其结论对于收卷机正确设计选型,提高收卷质量具有较大指导意义.     

Robust input design for nonlinear dynamic modeling of AUV

Input design has a dominant role in developing the dynamic model of autonomous underwater vehicles (AUVs) through system identification. Optimal input design is the process of generating informative inputs that can be used to generate the good quality dynamic model of AUVs. In a problem with optimal input design, the desired input signal depends on the unknown system which is intended to be identified. In this paper, the input design approach which is robust to uncertainties in model parameters is used. The Bayesian robust design strategy is applied to design input signals for dynamic modeling of AUVs. The employed approach can design multiple inputs and apply constraints on an AUV system’s inputs and outputs. Particle swarm optimization (PSO) is employed to solve the constraint robust optimization problem. The presented algorithm is used for designing the input signals for an AUV, and the estimate obtained by robust input design is compared with that of the optimal input design. According to the results, proposed input design can satisfy both robustness of constraints and optimality.     

Design of H(infinity) robust fault detection filter for linear uncertain time-delay systems

In this paper, the robust fault detection filter design problem for linear time-delay systems with both unknown inputs and parameter uncertainties is studied. Using a multiobjective optimization technique, a new performance index is introduced, which takes into account the robustness of the fault detection filter against disturbances and sensitivity to faults simultaneously. The reference residual model is then designed based on this performance index to formulate the robust fault detection filter design problem as an H(infinity) model-matching problem. By applying robust H(infinity) optimization control technique, the existence condition of the robust fault detection filter for linear time-delay systems with both unknown inputs and parameter uncertainties is presented in terms of linear matrix inequality formulation, independently of time delay. In order to detect the fault, an adaptive threshold which depends on the inputs is finally determined. An illustrative design example is used to demonstrate the validity of the proposed approach.