机械系统可靠性设计论析

本文根据实际,分析了现代机械系统可靠性设计遇到的几点困难,即机械系统可靠性设计程序难以统一、机械系统故障复杂多样化、机械系统设计的可靠性和耐久性并重、机械系统可靠性难以预计等,对此提出了四点对策即提高机械系统标准化、灵活增减系统元部件数量、提高重点部位零部件的可靠性、设置监控系统,安排专业人员定期进行维修等,帮助促进提高机械系统的可靠性设计。     

分析机械可靠性设计的内涵与递进

为了跟上现代化机械系统发展的速度和要求,研究和提高机械产品的可靠性势在必行。机械可靠性直接的关系着机械系统运行的质量和产品的性能,甚至关系着人们的生命安全。然而我国机械产品的可靠性设计水平和国际设计水平还有着很大的差距,这也成为了制约我国机械业发展创新的难题,分析机械可靠性设计的内涵与递进,是本文的主旨。     

机械产品的可靠性设计方法研究

机械产品的可靠性设计是确保机械产品质量的重要基础,文章在对机械产品可靠性概念进行阐述的基础上,对机械产品的可靠性设计内涵与递进进行探讨,最后从可靠性优化设计、可靠性灵敏度设计和可靠性稳健设计等方面出发对机械产品的可靠性设计进行分析。     

飞机机械故障诊断智能专家系统研究

飞机在机械系统当中属于高端的装备,伴随当前航空技术发展速度进一步加快,很多先进的生产方法应用到飞机生产中,飞机的机械系统也开始变得越来越复杂,其可靠性和安全性逐步变成飞机维修保养过程中重点研究的问题,智能专家系统是确保飞机可靠性的重要检测系统,越来越多的机械工程师开始重视飞机机械故障诊断智能专家系统,本文重点分析研究飞机机械诊断智能专家系统,以供参考。     

机械系统的可靠性模糊优化设计

系统可靠性模糊优化设计既考虑了随机性因素对系统的影响,又考虑了模糊性因素对系统的影响,其优化的结果往往比普通优化设计、可靠性设计、模糊优设计的结果要好。论述了机械系统的可靠性模糊优化设计方法,通过应用实例来说明这种设计方法的特点。     

考虑多模相关的机械系统可靠度优化模型

本文对多模相关的机械系统可靠度优化模型进行研究。由于机械产品的失效模式多、统计困难等原因造成机械可靠性为机械领域的研究难点。优化的二阶界限理论在界限区间宽度上更具有优势,足以满足普遍的可靠度精确计算要求,适合机械系统可靠性优化和评估问题。     

机械故障的形成及其特性分析

本文根据机械系统的使用与维修特点,阐述了机械技术状态的变化及其故障形成的一般过程,分析了机械故障的基本特性,指出了机械故障研究中应考虑的问题,对开展机械故障、维修与可靠性的研究具有一定意义。     

微型机械设计基础研究

微型机械系统在设计时,由于存在一些基础问题没有解决,使微型机械的发展比较缓慢。本文就微型机械设计基础研究的重要性做了研究,希望可以给设计师在微型机械设计中带来一些灵感。     

机械故障的形成及其特性分析

本文根据机械系统的使用与维修特点,阐述了机械技术状态的变化及其故障形成的一般过程,分析了机械故障的基本特性,指出了机械故障研究中应考虑的问题,对开展机械故障、维修保养和可靠性的研究具有一定的指导意义.     

浅议汽车零部件可靠性灵敏度计算和研究

汽车零部件特有的灵敏感应、可靠特性的层级,密切关联着整车性能。为此,有必要明辨灵敏度解析的路径、可靠性的辨识及运算方式。正态分布范畴内的参数变更,会影响配件固有的性能。拟定了细化特性的微机程序,利用编排得来的这种流程,能够提快运算速率,获取关涉可靠特性的信息,这就为接续的运算供应了参照。     

Bond graph based sensitivity and uncertainty analysis modelling for micro-scale multiphysics robust engineering design

Components within micro-scale engineering systems are often at the limits of commercial miniaturization and this can cause unexpected behavior and variation in performance. As such, modelling and analysis of system robustness plays an important role in product development. Here, schematic bond graphs are used as a front end in a sensitivity analysis based strategy for modelling robustness in multi-physics micro-scale engineering systems. As an example, the analysis is applied to a behind-the-ear (BTE) hearing aid.By using bond graphs to model power flow through components within different physical domains of the hearing aid, a set of differential equations to describe the system dynamics is collated. Based on these equations, sensitivity analysis calculations are used to approximately model the nature and the sources of output uncertainty during system operation. These calculations represent a robustness evaluation of the current hearing aid design and offer a means of identifying potential for improved designs of multiphysics systems by way of key parameter identification.     

Computer Models of Hysteresis in Mechanical and Magnetic Components

There is a strong analogy between mechanical structural elements and magnetic circuit components which can be extended to include hysteretic energy losses associated with yielding in mechanical systems and saturation in magnetic components. Procedures for developing finite state models of hysteretic components are presented using a small number of basic elements. Using bond graph techniques, it is shown that, when dual structural models are used, elements may be assembled in arbitrary numbers to achieve any desired accuracy without problems of derivative causality. The reason for the dual structure can be seen from physical reasoning. The shape of the hysteresis curve for magnetic materials generally requires more elements for a given degree of approximation than the shape of the typical mechanical hysteresis curve.     

Optimized sliding mode current controller for power converters with non-minimum phase nature

This paper proposes a unified method to design an optimized type of the hysteresis modulation-based sliding mode current controller for non-minimum phase power converters in continuous conduction mode. The traditional sliding mode controlled converters have a slow transient voltage response at heavy loads, a large overshoot at light loads and during abrupt output resistance variations. To solve these problems, an optimized feedback control scheme is used according to the output resistance to adjust the coefficients of the controller. The basic idea of this controller is to suggest a new way for reduction of the sensitivity function amplitude of the closed loop system. The presented approach is developed for three basic DC/DC converters; i.e. boost, buck-boost and quadratic boost converters. Generally, the certain advantages of the suggested control approach are: (i) a fast transient response can be achieved in heavy load conditions, (ii) the voltage overshoot can be effectively reduced during load variations; (iii) the transient voltage overshoot can be eliminated in light load conditions; (iv) the closed loop control sensitivity can be reduced and therefore, the performance specification of a control system can be improved compared with the conventional sliding mode current control. To show the reliability of the suggested control scheme, simulations and experimental results for the derived systems are developed. Several conditions are performed to confirm the effectiveness of the proposed controller.     

Numerical issues in backstepping control: Sensitivity and parameter tuning

The backstepping-based adaptive tuning functions design is a control-scheme for uncertain systems that ensures reasonably good stability and performance properties of the closed loop. The complexity of the controller makes inevitable the use of digital computers to perform the calculation of the control signal. This paper addresses the issue of the numerical sensitivity of this control scheme. It is shown that while the increase of the design parameters may be desirable to achieve a good transient performance, it harms the control signal as this increase introduces large high-frequency components due to the numerical errors. The presented results suggest that it is necessary a certain compromise between the choice of the design parameters and the numerical precision of the tools involved in the control design. This compromise can be quantified by explicit expressions.     

Stability-equation method for sampled-data systems

This paper presents a new transformation by which the stability-equation method can be applied for analysis and design of sampled-data systems. New stability criteria applicable to systems with transfer function having both real and complex coefficients are presented. Several kinds of examples are considered with computer results given.     

空间光学遥感器的计算机辅助热分析方法

介绍了一套空间光学遥感器的计算机辅助热分析方法 ,包括热平衡计算、热弹性分析、热光学分析、热光学灵敏度分析以及热设计方案评价等。热平衡计算用来预示遥感器的温度分布 ,热弹性分析用来计算热致变形和面型变化 ,热光学分析讨论热致位移和面型变化对成像质量的影响 ,热光学灵敏度分析则讨论不同形式的温差变化对成像质量影响的敏感程度。通过上述分析 ,能够弄清空间热环境对遥感器温度分布以及温度分布对成像质量的影响 ,进而提出热控制指标、制定合理的热设计方案。在工程任务的实际应用中表明该方法是可行的     

考虑风险偏好和属性约简的熵可靠性决策模型

针对属性值为区间数的大量属性决策问题,提出考虑决策者风险偏好和属性约简的熵可靠性决策模型。首先引入风险偏好因子将决策者进行分类,然后提出基于熵可靠性的属性约简方法并提取有效属性,匹配相应的信息熵权重确定方法和排序方法进行方案排序和择优,通过案例分析验证该方法的科学合理性;并通过选取不同的风险偏好因子,对决策对象排序结果进行灵敏度分析。结果表明随着决策者风险偏好程度的增加,决策属性保留个数递减;最后经算法对比表明该算法考虑决策信息的可靠性,减少信息损失且计算简便。     

Design and evaluation of information systems

A perspective is presented to bring into focus the state-of-the-art and development of methods and criteria which relate to the problem of design and performance evaluation of information systems. Two major aspects of design and evaluation are considered. These are the initiation, planning, development and testing of new information systems, to include modification of existing structures; and the appraisals and measurement of operational systems and their components. A taxonomy of information systems is presented in order to provide for a basis of organized evaluation of system performance.     

Parasitic tolerant designs of sampled data filters using switched capacitors and unity gain amplifiers

New and systematic procedures are presented for realizing sampled data filter (SDF) functions using switched capacitors (SCs) and unity gain amplifiers (UGAs). The procedures are attractive and simple to implement. Any SDF, recursive or non-recursive and of any order, can be realized using the methods presented. The designs of biquadratic SDFs is discussed in detail. The resulting realizations possess the property that the numerator and denominator coefficients of the SDF functions can be controlled by independent capacitance ratios. This makes the filters attractive for adaptive applications. The sensitivity properties of the resulting filters are analyzed and guidelines given for obtaining low sensitivity realizations. A method is also suggested to make the filters relatively insensitive to the parasitic capacitances in the circuit. Finally, a step by step procedure, easily implemented in a computer, is given. Starting from the given analog filter specifications, the method yields a design that has very low sensitivity, uses minimum total capacitance and is tolerant of the various parasitic capacitances in the circuit. Experimental results show very good agreement with the theoretical analysis.     

基于尺寸设计变量的声场-结构耦合系统的敏度分析

本文应用有限元方法对声场-结构耦合系统进行数值模拟和灵敏度分析.通过在结构设计阶段数值方法的研究,对耦合系统基于尺寸设计变量的特征频率和特征向量的灵敏度进行了分析,并通过数值算例的结果表明了算法的正确性,可为耦合系统的声学性态优化设计提供理论和算法基础.