Fixture knowledge model development and implementation based on a functional design approach

The development of a knowledge model applied to fixture design is a complex task. The main purpose of such model is the development of a knowledge-based application to assist fixture designers. It comprises a detailed specification of the types and structures of data involved in the execution of the inference process needed to create a fixture solution for machining a raw part. A development method together with a knowledge model for automating fixture design is proposed. The development was divided into three parts: Design Process Model, definition of Top-level functional functions and Product Knowledge Model. Adopting a functional design approach, the fixture design solution was created in two levels: functional and detailed. The functional level is based on fixture functional elements and the detailed one is based on fixture commercial elements. The definitions and concepts used in the application are specified in several Units of Knowledge (UoK) that comprises the Fixture Knowledge Model. Common Knowledge Analysis and Design Structuring (CommonKADS), Methodology and software tools Oriented to KBE Applications (MOKA), Integrated DEFinition for Function Modelling (IDEF0) and Unified Modelling Language (UML) are the methodologies and techniques used in the proposed method. Finally, a prototype KBE application for fixture design was developed.     

A method and advisor tool for multimedia user interface design

This paper describes a multimedia user interface design method and a design assistant tool which supports the method. The method covers specification of user requirements and information architecture, selection of appropriate media to represent the information content, design for directing attention to important information and interaction design to enhance user engagement. Guidelines for media selection and design for attractiveness, i.e. usability and user experience, are given. The method was evaluated in a case study design of a crowd control simulation training system, which demonstrated the method was usable and gave good solutions against an expert gold standard design. The tool provides advice on media selection and attention effects that match specification of the information content expressed as information types and communication goals. A usability evaluation was carried out to measure the usefulness and effectiveness of the tool in comparison to the method, and the results showed that the tool has a positive impact on multimedia design.     

Towards the design and development of a knowledge-based universal modular jigs and fixtures system

Jigs and fixtures are one of the important aspects of manufacturing. Parts may have different sets of fixturing requirements and call for different design strategies. Although there are numerous possibilities for fixture designs, a few basic configurations are clearly identifiable. Computer aided design (CAD) has done a little in assisting designers to design jigs and fixtures, making decisions of the best design selection, and providing designers with suggestions. The goal of this paper is to develop and document the design parameters and specifications utilized in jigs and fixtures design using universal modular jigs and fixtures design system (UMJFS). This is the first step to develop a knowledge-based Jigs and Fixture design and selection system. This application has the advantages of making the fixture design information completely modular and transparent, providing better match to the working conditions, reducing lead-time, and generally providing a significant enhancement of fixture productivity and economy. UMJFS has different standard and modular elements. This makes jigs and fixtures elements interchangeable and reusable. Designing a UMJFS then becomes a task of selecting and assembling the proper elements together.     

A CAD-Based hierarchical approach to interference detection among fixture modules in a reconfigurable fixturing system

A reconfigurable fixturing system has been developed for a computer-integrated assembly environment. The fixturing system employs a number of fixture modules which are set-up, adjusted and changed automatically by the assembly robot. A dedicated software program has been developed for the design, analysis, and verification of the fixture layout. The software program has been integrated with a commercially available computer-aided design (CAD) package to provide a user-friendly platform for modeling and display purposes. The robot program for setting up, adjusting, and dismantling the designed fixture is generated automatically. Interference between fixture modules during the fixture construction may arise due to incorrect selection of the fixture contact points at the design stage. The objective of the work described here is to develop a hierarchical approach for calculation of interference between fixture modules in a reconfigurable fixturing system. The formulation for the interference detection employs geometrical constraints as the basis. The approach does not require detailed simulation of the fixture construction for interference detection.     

An integrated fixture planning and analysis system for machining processes

Fixture planning is an important part of computer-aided process planning (CAPP), which is the link between design and manufacturing in a CIM environment. This paper presents a rational approach to computer-assisted fixture planning (CAFP), emphasizing integration of fixture planning with process planning, an issue that has not been adequately addressed until very recently. A systematic approach to fixture selection is outlined for planning of modular fixtures. A prototype CAPP-CAFP system has been developed at UCLA and linked to a commercial CAD system, namely, CADAM. Part design information can be extracted from the CAD model and multiple-view engineering drawings of a part stored in the CADAM system. Modular fixture elements can be selected automatically by the CAPP-CAFP system and the generated fixture layout can be displayed on the screen. Included also in the system is a fixture analysis module for verification and rationalization of a fixturing scheme. The force analysis module has a built-in local optimization routine that can determine the clamping forces of more reasonable magnitudes. The friction forces between the fixture and the workpiece can also be considered for simple cases.     

A knowledge based system for the integrated design and manufacture of round broach tools

A complete knowledge based procedure for the design and manufacture of a round hole broach tool is described. The knowledge based design system (KBDS) produces a tool specification from user inputs describing the task to be performed. These design results are then used by the knowledge base to generate a geometric CAD/CAM representation, which can be utilized directly to display a drawing of the tool or to generate a CNC program for producing it. The process of formulating a knowledge-based design system demonstrates: the integration of expertise from experts, handbooks and theory; the awareness of restrictions on the scope of design that can be handled by a given system: the use of failure handling mechanisms to detect design failures and either adjust the emerging design or indicate infeasibility.     

一种星载软件配置流程管理工具的设计

星载软件配置管理是星载软件工程化的一项重要内容,目前国内的软件配置管理基本上是采用国外的通用配置管理工具,由于工具没有和具体的流程相结合,因此对软件的出入库流程只能采用手工管理的方式;为了解决手工方式配置管理手续繁琐、效率低下及容易导致文实不符等问题,这里介绍了一种自主开发的星载软件配置流程管理工具的设计方案,它基于B/S结构,实现了配置管理流程审批过程的电子化和网络化,还通过和通用配置管理工具ClearCase接口,实现了软件源程序和目标代码的出、入库随流程审批过程自动完成;该工具大大提高了星载软件配置管理的质量和效率。     

Derivation of a ‘designer's guide’ for interactive ‘grey-box’ identification of nonlinear stochastic objects

The problem of using an ‘identification tool box’ for the design of ‘grey-box’ models for nonlinear dynamic objects is non-trivial. The design is an interactive process, and it is not given a priori in what order to execute the various subtasks that the tool box supports what design parameters to manipulate and how to interpret the intermediate results. The difficulties are enhanced when the uncertainty of the designer's a-priori information and the quality of the experiment are such that a model contains other stochastic elements than measurement error.

This paper derives a systematic procedure for design of such models, assuming a generic tool box. The origin is the basic procedure commonly used in natural sciences, namely that of repeated refinement and falsification of hypotheses. The derivation is based on statistical decision theory and leads to the specification of a ‘designer's guide’ for grey-box identification. The procedure has been tested on two industrial processes, using the IdKit tool box, and a prototype of the guide has been implemented as a Unix shell. A simulated example illustrates the procedure.     

Automated fixture configuration for rapid manufacturing planning

The wide adoption of agile manufacturing systems has necessitated the design and use of fixtures or work holding devices that have in-built flexibility to rapidly respond to part design changes. Despite the availability of reconfigurable fixtures, practical fixture configuration largely remains an experience driven manual activity to enable customization for varying workpiece geometry, and most automated solutions do not scale well to accommodate such variation. In this paper, we address the problem of rapidly synthesizing a realistic fixture that will guarantee stability and immobility of a specified polyhedral work-part. We propose that the problem of automated fixture layout may be approached in two distinct stages. First, we determine the spatial locations of clamping points on the work piece boundary using the principles of force and form closure, to ensure immobility of the fixtured part under external perturbation. In particular, we show that the candidate restraints mapped to the six dimensional vector space of wrenches (force–moment pairs) may be hashed in a straightforward manner to efficiently generate force closure configurations that restrain part movement against large external wrenches. When clamps are allowed to exert arbitrarily high reaction forces on the part, the spatial arrangement of the clamping locations ensures the part is in form closure. On generating force/form closure configurations, the chosen locations are matched against a user-specified library of reconfigurable clamps to synthesize a valid fixture layout comprising clamps that are accessible and collision free with each other and the part. Additionally, in the case of determining machining setups the clamps are chosen to avoid collisions with the moving cutting tool. We demonstrate fast algorithms to perform both location selection and fixture matching, and show several results that underscore the practical application of our solution in automated manufacturing process planning.     

Analysis and optimization of fixture under dynamic machining condition with chip removal effect

Dynamic interactions in the tool–workpiece and workpiece–fixture systems significantly impinge on the quality of finished workpieces. The presented simulation system integrates the effects of workpiece fixture dynamics with the other factors contributing to the machining process dynamics. It provides more accurate prediction of the process output which helps in the design of the optimum fixture configuration prior to the production stage. Modelling of the frictional contact behaviour between the fixture element and the workpiece helps to improve the prediction accuracy of the simulation system which accelerates the convergence to the optimum fixture configuration design and consequently improves the machined part dimensional accuracy and geometric integrity. The developed simulation is capable of modelling complicated part geometries by interfacing with commercial ANSYS.V10^® packages. This research work minimizes the deformation of workpiece using integrated optimization tool of Genetic algorithm (GA) and ANSYS Parametric Design Language (APDL) of finite element analysis. The same layouts given by the above optimization tool are used in the experimental setup and it is found that the improved geometric tolerance of squarness and flatness of the given workpiece. The chip removal effect and frictional contact between the workpiece and the fixture elements are taken into account based on element death technique and nonlinear finite-element analysis. A Case study of an open slot milling process illustrates the application of the proposed improved geometric tolerance approach.     

Iterative automatic test generation method for telecommunication protocols

Standardized languages used for protocol specification provide an excellent basis for both automatic and manual test generation. Test generation is composed of two steps, the derivation of test cases from the specification, and the selection of the test cases to be included in the final test suite in order to reduce its execution time. This article proposes a new method that aims to decrease the total number of test cases generated automatically by a test derivation algorithm and at the same time to reduce the computation requirements for the test selection procedure. It creates an iteration cycle on the model of evolutionary algorithms, where the test derivation and selection are done simultaneously. In each cycle first a “small” test suite is derived then optimized, evaluated and finally compared to the best suite so far. It is kept as the best suite, if it is found better according to some well-defined evaluation criteria and test suite metrics. This iteration condition is based on the test selection criteria. The article presents an experiment where iterative algorithms are compared to two simple test derivation methods from different aspects.     

An IKBS for integrating component design to tool engineering

Abstract: Component design and tool engineering functions are two sequentially related activities. Many additional benefits may arise if these activities can be effectively integrated together within a central environment. The principal aim of the research described in this paper is to develop a component design and tool engineering Intelligent Knowledge Based System (IKBS), called Holdex to demonstrate such a concept. It is an implementation designed to deduce the planning, design, tooling, procurement and scheduling information at the component design stage. It also assists the component designers in the operation of a Computer Aided Design (Cad) system and leads them towards the rationalisation of resources by encouraging standardisation of designs. A major benefit to arise from the provision of such assistance is to facilitate the tasks of executing the production engineering functions. The range of functions performed by Holdex includes the specification of a set of cutting tools; planning a set of pre-machining requirements; recommendation of the appropriate machine tool and manning level; and the automated design of fixtures. Towards this end, this research aims to provide a foundation for enabling industry to manufacture with the least amount of manual interpretation.     

Design and implementation of a relational data base for automated process planning

The function of process planning in a manufacturing facility is to identify the processes and the machines required to convert a design into its final form. Majority of the process plans are still made manually. The degree of the process plan detail varies with the shop environment. A feature-based process planning system which interacts with the SDRC I-DEAS solid modeling software is presented. The system operates under the UNIX environment. A relational database model which incorporates manufacturing details including the operation selection, machine selection, tool selection, fixture selection, etc. was developed and implemented. This relational database was structured using Microsoft SQL SERVER for the PC multi-user environment. This database is part of an ongoing research project on automated process planning and scheduling and primarily focuses on prismatic parts. The developed routines generate the Overall Removable Volume (ORV) graphically by comparing the desirable design to the blank work piece. The routines then decompose the ORV into various General Manufacturing Features (GMF) based on concave edges. The recognition routine captures geometrical and topological information and identifies the shape of each GMF. An expert system (using CLIPS expert system shell) analyzes the GMFs and determines appropriate operation(s) for the designed part. The developed expert system is capable of recommending the suitable machines, tools, fixtures, etc.     

Consistent specification of interface suites in UML

The paper motivates and describes a model oriented approach for consistent specification of interface suites in UML. An interface suite is a coherent collection of interfaces defining interactions that transcend component boundaries. The specification of interface suites contains diagrammatic views and documentation, but it is extended with templates for structured specifications deriving from the ISpec approach. To guarantee that the specification views, documentation and templates are consistent, a specification model has been constructed. The model contains both structural and behavioural information, represented in the form of sequences of carefully designed tuples. The model provides the underlying structure for the tool supporting the design process. The tool directs the designer to specify all elements of the model in a consistent way. The specification is collected both by customized specification templates and by diagrams. The documentation and the diagram elements – both derived from the template information – are automatically generated. This prevents errors and provides specification consistency. Initial submission: 15 February 2002 / Revised submission: 20 September 2002 Published online: 2 December 2002 RID="*" ID="*"Supported by PROGRESS grant EES.5141 and ITEA DESS grant IT990211.     

Applying RBR and CBR to develop a VR based integrated system for machining fixture design

A fixture is a special tool used to accurately and stably locate the workpiece during machining process. Proper fixture design improves the quality and production of parts and also facilitates the interchangeability of parts that is prevalent in much of modern manufacturing. This study combines the rule-based reasoning (RBR) and case-based reasoning (CBR) method for machining fixture design in a VR based integrated system. In this paper, an approach combines the RBR and fuzzy comprehensive judgment method is proposed for reasoning suitable locating schemes and locating features. Based on the reasoning results, a CBR method for machining fixture design is then presented. This method could help designers, by referencing previous design cases, to make a conceptual fixturing solution quickly. Finally, the implementation of proposed system is outlined and cases study has been used to demonstrate the applicability of the proposed approach.     

用Petri网描述程序精化中的循环不变式

形式化方法把程序看成规范,形式化开发方法包括形式规范和规范（程序）的精化。精化演算方法能够通过演算的方式,把规范逐步精化为程序。然而,演化的过程依赖于开发人员的经验,整个过程全部都是手动的。形式化方法的最高目标是软件自动化,使得能从规范自动开发出正确的程序。因而用Petri网来描述程序精化中的循环不变式,希望以此作为软件自动化的一个探索。