Modifying LOTOS Specifications by Means of Automatable Formula-Based Integrations

The use of good (formal) specifications of software components produces a good characterization of their functionalities. This fact eases the modifiability of a module specification due to a change of requirements or to the need of an enhancement of its functionalities after the delivery to the users, and then, in general, eases also the reusability of a module. Moreover, if existing modules have a specification not based on a natural language but on the well-given syntax of a specification language, it is possible to process the needed modifications in an automatic way. This work presents a method to derive the modifications of the specification of an existing module (given by means of the LOTOS language) from a characterization of the environment, in which the new module has to be used, given by means of temporal logic formulae. The method consists of tableau-based rules that build the due modifications, and always produces a fitting solution for formulae that can be satisfied and belong to a given class.     

面向装配的变动几何约束网络的生成方法研究

提出变动几何约束网络概念，并将此网络应用于计算机辅助公差设计领域，根据公差与配合的分类，定义3类变动几何约束，基于图论和TTRS理论提出配合树和回路概念，给出配合树的性质和回路的生成规则，基于CAD系统中功能表面间的配合关系，研究了变动几何约束网络的生成方法，通过变动几何约束网络在公差类型的生成和尺寸链的产生中的应用，验证此方法的有效性。     

Generation of functional tolerancing based on positioning features

The aim behind applying functional tolerancing to a mechanism is to widen the tolerances used in parts manufacturing according to the effective functional properties of the product. This step may be performed using CAD systems and geometrical specifications defined by ISO standards. The present paper will describe the complete process involved in functional tolerancing. The CLIC tolerancing method has been implemented within an Excel software environment. CAD models for parts have been imported via a STEP interface. According to this approach, the designer describes the assembly process; the CLIC system then determines the functional requirements corresponding to the joints between parts and generates all datum reference frames and tolerancing of set-up surfaces in compliance with ISO standards. CLIC also determines both the geometrical conditions of minimum distances in order to avoid interference between parts and the conditions for assembling small standard components. The designer next adds other functional requirements. For each such requirement, a tolerancing process creates location and orientation specifications for influential parts using datum reference frames derived during the previous stage. Excel formulae focusing on the sum of tolerances are generated using a three-dimensional statistical approach. Moreover, the tolerance database allows optimizing the tolerances and nominal dimensions of parts.     

Incremental mining of information interest for personalized web scanning

Businesses and people often organize their information of interest (IOI) into a hierarchy of folders (or categories). The personalized folder hierarchy provides a natural way for each of the users to manage and utilize his/her IOI (a folder corresponds to an interest type). Since the interest is relatively long-term, continuous web scanning is essential. It should be directed by precise and comprehensible specifications of the interest. A precise specification may direct the scanner to those spaces that deserve scanning, while a specification comprehensible to the user may facilitate manual refinement, and a specification comprehensible to information providers (e.g. Internet search engines) may facilitate the identification of proper seed sites to start scanning. However, expressing such specifications is quite difficult (and even implausible) for the user, since each interest type is often implicitly and collectively defined by the content (i.e. documents) of the corresponding folder, which may even evolve over time. In this paper, we present an incremental text mining technique to efficiently identify the user's current interest by mining the user's information folders. The specification mined for each interest type specifies the context of the interest type in conjunctive normal form, which is comprehensible to general users and information providers. The specification is also shown to be more precise in directing the scanner to those sites that are more likely to provide IOI. The user may thus maintain his/her folders and then constantly get IOI, without paying much attention to the difficult tasks of interest specification and seed identification.     

Tolerance specification of robot kinematic parameters using an experimental design technique—the Taguchi method

This paper presents the tolerance specification of robot kinematic parameters using the Taguchi method. The concept of employing inner and outer orthogonal arrays to identify the significant parameters and select the optimal tolerance range for each parameter is proposed. The performance measure based on signal-to-noise ratios (S/N) using the Taguchi method is validated by Monte Carlo simulations. Finally, a step-by-step tolerance specification methodology is developed and illustrated with a planar two-link manipulator and a five-degree-of-freedom Rhino robot.     

Integrated product and process design: a multi-objective modeling framework

In this paper we present an analytical multi-objective framework for the concurrent design of product and processes. The objective is to simultaneously consider the tolerance specification on the product or the component dimensions along with the selection of the manufacturing processes. For this purpose we consider three objectives: to minimize unit cost, to minimize quality loss and to minimize manufacturing lead time. We characterize the properties of the non-dominated solutions. These solutions provide flexibility needed in an agile manufacturing environment. The min–max approach is used to obtain trade-off solutions.     

A generic deviation-based approach for synthesis of tolerances

In this paper, a generic model for the synthesis of tolerances for manufactured parts is presented. The model uses a method of transforming traditional tolerance specifications (as defined in ASME Y14.5M) to a generalized coordinate system (hereinafter referred to as deviation space). Small displacement torsors (SDTs) have been used for representing the deviations. The tolerance synthesis method is formulated as a constrained nonlinear optimization process. Three different types of constraints have been considered for the optimization process: 1) representation of assemblability; 2) mapping of tolerance specification to deviations; and 3) functional requirements. A new deviation-based cost of manufacturing model has been proposed. A working module of the scheme has been implemented and the process has been elaborated with two examples. The possibility of extension of the model and scope for further generalization have been discussed. Note to Practitioners-This paper presents an optimization method for finding tolerance values for different features of an assembly of manufactured parts. Determination of different types of tolerances and their exact values for critical features of any part has been an ad-hoc process; it has been mostly experience-based till recent time. In this paper, efforts have been made to establish a strong mathematically oriented method for synthesis of tolerances. The procedure attempts to minimize cost of manufacturing while the functionality and assemblability are satisfied. It is a generalized method and could be applied for designing rigid manufacture parts. For practical usage, this method should be integrated with three-dimensional computer-aided design packages as a tolerance synthesis module for integrated tolerance design.     

Program Synthesis from Formal Requirements Specifications Using APTS

Formal specifications of software systems are extremely useful because they can be rigorously analyzed, verified, and validated, giving high confidence that the specification captures the desired behavior. To transfer this confidence to the actual source code implementation, a formal link is needed between the specification and the implementation. Generating the implementation directly from the specification provides one such link. A program transformation system such as Paige's APTS can be useful in developing a source code generator. This paper describes a case study in which APTS was used to produce code generators that construct C source code from a requirements specification in the SCR (Software Cost Reduction) tabular notation. In the study, two different code generation strategies were explored. The first strategy uses rewrite rules to transform the parse tree of an SCR specification into a parse tree for the corresponding C code. The second strategy associates a relation with each node of the specification parse tree. Each member of this relation acts as an attribute, holding the C code corresponding to the tree at the associated node; the root of the tree has the entire C program as its member of the relation. This paper describes the two code generators supported by APTS, how each was used to synthesize code for two example SCR requirements specifications, and what was learned about APTS from these implementations.     

三维工艺模型标注尺寸构造方法研究

根据工艺和拓扑相关表面(TTRS)理论识别三维工艺模型中全部面的特征,获得零 件的 TTRS 和相应最小几何基准元素(MGDE)的几何与拓扑信息,提取工艺模型标注元素。根据 MGDE 与基准的相对位置对工艺模型标注元素进行分类用于构造标注尺寸。标注元素存在冗 余,针对 3 种冗余情况提出了相应的冗余标注元素消除规则,并依据规则实现了冗余消除。对 于 6 种尺寸标注类型,给出了其权值的计算方法,并以此确定尺寸标注次序。针对生成的标注 尺寸中可能存在冗余的情况,运用图论方法消除冗余标注尺寸,并给出了冗余标注尺寸消除算 法流程图。构建了完整的尺寸标注集,实现了工艺模型三维标注尺寸的构造。基于 UG/Open Grip 开发了三维标注尺寸构造与显示模块,实现了上述算法。     

Teaching formal methods lite via testing

A new style of formal methods course is described, based on a pragmatic approach that emphasizes testing. The course introduces students to formal specification using Z, and shows how formal specification and testing can benefit each other, in both the validation and verification phases. It uses a tools‐based approach, with practical work that reinforces formal specification techniques as well as traditional software engineering skills, such as unit and system testing, inspection and defensive programming with assertions. The two main results are to identify several practical uses of formal specifications that are not widely practised or taught, and to demonstrate that teaching them results in a more interesting and relevant formal methods course. Copyright © 2001 John Wiley & Sons, Ltd.     

Method for automating digital fixture-setups that are optimal for machining castings to minimize scrap

The motivation for this paper is to describe a method for lowering the cost of finishing large castings that have machined surfaces for attaching other components. Considerable time is required to set-up each cast part on a machine-tool, sometimes taking longer than the machining itself, and errors in set-up can result in scrapping expensive parts or attempts to salvage them by rework. Although the focus of the paper is to demonstrate a new technology and software for set-up prior to the machining of iron/aluminum/steel sand castings, the same technology also is applicable to large welded assemblies on which finished machining occurs. In this paper, we outline a method, currently being implemented, that can predictively, and off-line, identify the adjustments needed to position and orient each part in its fixture before machining operations begin so that, after machining, all finished features will lie in their tolerance zones. Computer models first simulate all the to-be-machined (TBM) surfaces and any contact points with the fixture by feature-fitting point clouds taken from selective scanning of the raw casting. The locations of these features are compared with their locations on the CAD model of the part. Then, by using the T-Map model for tolerances, all possible locations of the part in its machining fixture are identified so that all TBM faces lie in their tolerance-zones. An optimum location may then be chosen.     

A new calculation method for the worst case tolerance analysis and synthesis in stack-type assemblies

Productivity and industrial product quality improvements entail a rational tolerancing process to be applied as early as product design. Once functional conditions are defined, an optimal specification for each component in a mechanical system is to be developed. Despite numerous studies in this area, the problem is still far from solved. It may be decomposed into two stages: development of specifications based on standards, or qualitative synthesis, and calculation of tolerances. To the extent that these two sets of problems are related, we propose to address them in parallel. In this paper, we present an original method that enables us to solve these two problems for the case of serial assembly (stacking) without clearances. This method is based on the use of influence coefficients to obtain the relationship between the functional tolerance and the tolerances associated with the geometry of the mechanism’s interface surfaces. We will describe a calculation algorithm that helps obtain influence coefficients solely from the assembly’s geometric definition. Then, we will show that under our working hypothesis, this relationship is piecewise linear.     

Simultaneous optimal selection of design and manufacturing tolerances with alternative manufacturing process selection

Tolerance specification is an important part of mechanical design. Design tolerances strongly influence the functional performance and manufacturing cost of a mechanical product. Tighter tolerances normally produce superior components, better performing mechanical systems and good assemblability with assured exchangeability at the assembly line. However, unnecessarily tight tolerances lead to excessive manufacturing costs for a given application. The balancing of performance and manufacturing cost through identification of optimal design tolerances is a major concern in modern design. Traditionally, design tolerances are specified based on the designer’s experience. Computer-aided (or software-based) tolerance synthesis and alternative manufacturing process selection programs allow a designer to verify the relations between all design tolerances to produce a consistent and feasible design. In this paper, a general new methodology using intelligent algorithms viz., Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi Objective Particle Swarm Optimization (MOPSO) for simultaneous optimal selection of design and manufacturing tolerances with alternative manufacturing process selection is presented. The problem has a multi-criterion character in which 3 objective functions, 3 constraints and 5 variables are considered. The average fitness factor method and normalized weighted objective functions method are separately used to select the best optimal solution from Pareto optimal fronts. Two multi-objective performance measures namely solution spread measure and ratio of non-dominated individuals are used to evaluate the strength of Pareto optimal fronts. Two more multi-objective performance measures namely optimiser overhead and algorithm effort are used to find the computational effort of NSGA-II and MOPSO algorithms. The Pareto optimal fronts and results obtained from various techniques are compared and analysed.     

An expert system approach for die and mold making operations

In the modern manufacturing of sophisticated parts with 3D sculptured surfaces, die and mold making operations are the most widely used machining processes to remove unwanted material. To manufacture a die or a mold, many different cutting tools are involved, from deep hole drills to the smallest ball nose end mills. Since the specification of each tool is very different from each other, each mold or die is specific with their complicated shapes and many machining rules exist to consider, a great deal of expertise is needed in planning the machining operations. An expert system (DieEX) developed for this purpose is described in the present work. The geometry and the material of the workpiece, tool material, tool condition and operation type are considered as input values and various recommendations about the tool type, tool specifications, work holding method, type of milling operation, direction of feed and offset values are provided.     

Coupling experimental design—digital simulation of junctions for the development of complex tolerance chains

This paper presents a new functional tolerancing method developed for analyzing tri-dimensional variations of mechanical assemblies. The behavior of a junction is simulated with Microsoft EXCEL to quantify the influence of geometrical variations of a given part on a functional requirement. The solver determines the critical situation of the mechanism with respect to the contact constraints and the location and orientation tolerances. The result of this stage is introduced into an experimental design so as to define a relationship between the variation of the functional requirement and the geometric tolerances specified for the surfaces of the parts. The complete inequality ensuring tolerance synthesis is obtained by adding the defects of all junctions forming the vector loop.     

Specifications: Formal and informal—a case study

Formal specifications (algebraic) are given for an informally specified small subsystem of the Change Management Automatic Build System. A comparison of the two specifications shows that although informal specifications are easier to read, the formal specifications are clearer, specify operation domains precisely, define the interaction between the operations, show the incompleteness of the informal specifications and are devoid of implementation details. The formal specifications pointed to the need of a function not in the subsystem whose inclusion would improve the system design. This inclusion is now being considered. However, the use of algebraic specifications requires practice and experience. Although the formal specification of large systems is somewhat impractical at the moment, experience in using formal specifications can lead to better informal specifications.     

A specification schema for indenting programs

A two level specification of the functional behaviour of a class of indenting programs for Pascal is presented. The transformation that these programs perform on the input text is a composition of splitting input lines, altering the blank space between lexical tokens and computing the margin required in front of each of the split lines. The high level specification is given as a stylized Pascal grammar in Extended BNF. In contrast, the low level specifications, which are operationally closer to a program, and which define how syntactically invalid text is dealt with, require several mathematical functions that capture the essence of these basic transformations. The specifications of an indenting program for Pascal are then obtained as a further elaboration of these functions. Most indentation styles appearing in the literature can be specified with precision using methods developed in this paper. Our experience in this case study indicates that although specifications for real-life programs can be given using simple mathematics, the effort required is still considerable.     

Enabling metrology-oriented specification of geometrical variability – A categorical approach

In this paper a metrology-oriented specification schema is proposed to enrich the specification semantics with sufficient metrological information. It is designed particularly for applications where non-traditional measurement methods are applied; and it can also identify any redundancies, inconsistencies or incompletenesses of a specification. The proposed schema is based on category theoretical semantics which uses category theory as the foundation to model the semantics. A set of verification operations that derived from the measurement process was firstly formalised using the categorical semantics. Then a set of full faithful functors were constructed to map the set of verification operations to a set of specification operations. A set of simplification rules was then developed to deduce all of the necessary specification objects which are independent to each other. Then the residual specification objects provide a compact structure of the specification. Three test cases were conducted to validate the proposed schema. An industrial computed tomography (CT) measurement process for an impeller manufacturing using selective laser sintering (SLS) technique, was modelled and a set of independent specification elements was then deduced. The other two test cases for checking redundancy and incompleteness on general ISO specifications were carried out. The results show that the proposed schema works for proposing semantic enriched specification that are characterised by non-traditional measurement methods and for testing redundancy and incompleteness of specifications based on geometrical product specifications and verification (GPS) standards system.