A virtual prototyping approach to product disassembly reasoning

An important aspect of Design for the Life Cycle is assessing the disassemblability of products. After an artifact has completed its useful life, it must be disassembled then recycled, remanufactured or scrapped. Disassemblability of a product can be evaluated by performing disassembly activities on prototypes. Virtual prototyping (VP) is an alternative to hardware prototyping in which analysis of designs can be done without manufacturing physical samples. In recent years, disassembly processes have been generated either by using interactive or automated approaches, but these approaches have limitations. Interactive approaches require extensive user input usually in the form of answering questions, whereas automated approaches can only be used to generate disassembly processes for products with simple component configuration and geometry. In this paper automated and interactive techniques are combined, using VP, to generate complete disassembly processes of a product design. To support generation of disassembly processes of a product, a virtual environment and VP method were developed that will support disassembly activities performed by a designer. The product model of the virtual prototype is generated from the CAD model. The disassembly process model for the prototype is generated using automated reasoning techniques and is completed by interactively disassembling the product in the virtual environment. Extensions to automatic reasoning techniques to compute ranges of feasible directions of component removal were developed to facilitate the generation of the disassembly process. A scheme to represent the disassembly process for disassemblability evaluation was developed and implemented. In this paper a Chrysler LHS center console has been used to illustrate our approach of generating disassembly processes via VP.     

Integrated multi-layer representation and ant colony search for product selective disassembly planning

Selective disassembly plays an important role in product life cycle to meet requirements of the product repairing, reusing and recycling. An efficient disassembly plan is essential to minimize processing time in product maintenance for cost saving. This paper introduces a method for integration of the multi-layer product representation and the optimal search in product selective disassembly planning. The multi-layer representation is based on the product structure formed in product design. The method enables an efficient search for the disassembly sequence. Unlike the existing product representation methods, the multi-layer representation is a dynamic product data model integrated with an ant colony search process for a near optimal solution. Industrial applications have proven the method effectiveness.     

A framework for virtual disassembly analysis

Product reuse or recyclability is enhanced by designing the product for inexpensive and efficient disassembly. However, accomplishing enhanced product design requires design for disassembly (DFD) tools. This paper presents a disassembly framework that consists of design modules; both of these are embodied in the geometric DFD tool. These modules consist of different tasks including: selection of the appropriate disassembly method; producing an optimized disassembly sequence; evaluating a disassembly sequence for cost; producing design change recommendations. These considerations make a product easier to disassemble and therefore have potential benefit to the environment.     

A versatile virtual prototyping system for rapid product development

This paper presents a versatile virtual prototyping (VP) system for digital fabrication of multi-material prototypes to facilitate rapid product development. The VP system comprises a suite of software packages for multi-material layered manufacturing (MMLM) processes, including multi-toolpath planning, build-time estimation and accuracy analysis, integrated with semi-immersive desktop-based and full-immersive CAVE-based virtual reality (VR) technology. Such versatility makes the VP system adaptable to suit specific cost and functionality requirements of various applications.

The desktop-based VR system creates a semi-immersive environment for stereoscopic visualisation and quality analysis of a product design. It is relatively cost-effective and easy to operate, but its users may be distracted by environmental disturbances that could possibly diminish their efficiency of product design evaluation and improvement. To alleviate disturbance problems, the CAVE-based VR system provides an enclosed room-like environment that blocks out most disturbances, making it possible for a design team to fully concentrate and collaborate on their product design work.

The VP system enhances collaboration and communication of a design team working on product development. It provides simulation techniques to analyse and improve the design of a product and its fabrication processes. Through simulations, assessment and modification of a product design can be iterated without much worry about the manufacturing and material costs of prototypes. Hence, key factors such as product shape, manufacturability, and durability that affect the profitability of manufactured products are optimised quickly. Moreover, the resulting product design can be sent via the Internet to customers for comments or marketing purposes. The VP system therefore facilitates advanced product design and helps reduce development time and cost considerably.     

Artificial bee colony algorithm for solving sequence-dependent disassembly line balancing problem

In this paper, we consider a sequence-dependent disassembly line balancing problem (SDDLBP) with multiple objectives that requires the assignment of disassembly tasks to a set of ordered disassembly workstations while satisfying the disassembly precedence constraints and optimizing the effectiveness of several measures. Since the complexity of SDDLBP increases with the number of parts of the product, an efficient methodology based on artificial bee colony (ABC) is proposed to solve the SDDLBP. ABC is an optimization technique which is inspired by the behavior of honey bees. The performance of the proposed algorithm was tested against six other algorithms. The results show that the proposed ABC algorithm performs well and is superior to the other six algorithms in terms of the objective values performance.     

Computer-aided prototyping of production flows for a virtual enterprise

This paper presents a logistics framework to cope with the problem of planning and control of production flows processed on a set of work cells distributed among component firms of a virtual enterprise (VE). The constraints theory framework is employed to study constraint-based production flow coordination rules. The article discusses relationships linking structural parameters (e.g. buffer capacity, machine tool efficiency, and automated storage/retrieval systems) of VE components with material flow control guaranteeing efficient completion of work orders, and specified by such parameters as batch delivery periods, work-in-process (WIP) and make-span. The results are summarized in the form of a performance evaluation scheme. Examples using a software package that implements the proposed flow coordination methodology are provided.     

Communication support for prototyping projects

Communication plays a critical role in system development projects. In the paper we present our experiences with ‘communication consultants’ and ‘project diaries’, as a means of supporting system development projects using prototyping as a development strategy. Communication consultants are project members who are particularly concerned with all aspects of communication relating to a given project. Project diaries are a means of capturing the actual course of a project, and they reflect those project activities which are supplemental to conventional product documentation.     

On Building Prediction Systems for Software Engineers

Building and evaluating predictionsystems is an important activity for software engineering researchers.Increasing numbers of techniques and datasets are now being madeavailable. Unfortunately systematic comparison is hindered bythe use of different accuracy indicators and evaluation processes.We argue that these indicators are statistics that describe propertiesof the estimation errors or residuals and that the sensible choiceof indicator is largely governed by the goals of the estimator.For this reason it may be helpful for researchers to providea range of indicators. We also argue that it is useful to formallytest for significant differences between competing predictionsystems and note that where only a few cases are available thiscan be problematic, in other words the research instrument mayhave insufficient power. We demonstrate that this is the casefor a well known empirical study of cost models. Simulation,however, could be one means of overcoming this difficulty.     

Kansei engineering as a powerful consumer-oriented technology for product development

Kansei engineering was founded 30 years ago, as an ergonomics and consumer-oriented technology for producing a new product. When a consumer wants to buy something, he/she will have a kind of feeling and image (kansei in Japanese) in his/her mind. If the consumer's feeling could be implemented in the new product, he/she would be more satisfied with the product. Kansei engineering aims at translation of kansei into the product design field including product mechanical function. This is why it is called the consumer-oriented aspect. There are many products in Japan which have applied kansei engineering. Recently, it has also been applied to construction products as well as to community design.     

An efficient approach to human motion modeling for the verification of human-centric product design and manufacturing in virtual environments

The efficient and reliable human-integrated design of products and processes is a major goal of the manufacturing industry. Thus, numerous human-related product functionality and manufacturability aspects need to be verified, using simulation, in the context of the product development procedures. The natural representation of human motions in virtual environments is crucial for the reliability of the simulation results. In this context, the paper presents an efficient approach to human motion analysis and modeling with respect to the anthropometric parameters, based on real motion data. Statistical methods employed for the analysis of the data and additive motion models are derived. The models are capable of predicting human motion and driving digital humans in product and worker simulation environments. A specific test case is presented to demonstrate the application of the suggested methodology on a real industrial problem.     

A new integrated approach for engineering characteristic prioritization in quality function deployment

As a customer-driven quality improvement tool, quality function deployment (QFD) can convert customer requirements (CRs) into appropriate engineering characteristics (ECs) in product design and development. However, the conventional QFD method has been criticized for a variety of drawbacks, which limit its efficiency and potential applications. In this study, a new QFD approach integrating picture fuzzy linguistic sets (PFLSs) and the evaluation based on distance from average solution (EDAS) method is proposed for the determination of ranking order of ECs. The PFLSs are utilized to express the judgements of experts on the relationships among CRs and ECs. Then, the EDAS method is extended under picture fuzzy linguistic environment for the prioritization of the ECs identified in QFD. Moreover, a combined weighing method based on technique for order of preference by similarity to ideal solution (TOPSIS) and maximum entropy theory is established to calculate the weights of experts objectively. Finally, a product-service system design is provided to illustrate the effectiveness of the proposed QFD approach. The result shows that the manufacturer should pay more attention to “Meantime before failure”, “Warning feature” and “Quality of product manual”. Feedback from domain experts indicates that the integrated approach being proposed in this paper is more suitable for assessing and prioritizing ECs in QFD.     

How to model and implement connections between physical and virtual models for digital twin application

Digital twin (DT) is a virtual mirror (representation) of a physical world or a system along its lifecycle. As for a complex discrete manufacturing system (DMS), it is a digital model for emulating or reproducing the functions or actions of a real manufacturing system by giving the system simulation information or directly driven by a real system with proper connections between the DT model and the real-world system. It is a key building block for smart factory and manufacturing under the Industry 4.0 paradigm. The key research question is how to effectively create a DT model during the design stage of a complex manufacturing system and to make it usable throughout the system’s lifecycle such as the production stage. Given that there are some existing discussions on DT framework development, this paper focuses on the modeling methods for rapidly creating a virtual model and the connection implementation mechanism between a physical world production system at a workshop level and its mirrored virtual model. To reach above goals, in this paper, the discrete event system (DES) modeling theory is applied to the three-dimension DT model. First, for formally representing a manufacturing system and creating its virtual model, seven basic elements: controller, executor, processor, buffer, flowing entity, virtual service node and logistics path of a DMS have been identified and the concept of the logistics path network and the service cell is introduced to uniformly describe a manufacturing system. Second, for implementing interconnection and interaction, a new interconnection and data interaction mechanism between the physical system and its virtual model for through-life applications has been designed. With them, each service cell consists of seven elements and encapsulates input/output information and control logic. All the discrete cells are constructed and mapped onto different production-process-oriented digital manufacturing modules by integrating logical, geometric and data models. As a result, the virtual-physical connection is realized to form a DT model. The proposed virtual modeling method and the associated connection mechanism have been applied to a real-world workshop DT to demonstrate its practicality and usefulness.     

一类不确定模糊动态时滞系统保成本控制

针对一类不确定非线性动态时滞系统，利用模相T—S模型，通过状态反馈对保成本控制问题进行研究。应用线性矩阵不等式给出模糊闭环系统渐近稳定的充分条件，保证了所有允许的不确定闭环系统是稳定的，而且对于一个给定的二次型成本函数，舱保证闭环成本不超过某个界。仿真结果表明所提出的控制方法是有效的。     

Comparing a knowledge-based and a data-driven method in querying data streams for system fault detection: A hydraulic drive system application

The field of fault detection and diagnosis has been the subject of considerable interest in industry. Fault detection may increase the availability of products, thereby improving their quality. Fault detection and diagnosis methods can be classified in three categories: data-driven, analytically based, and knowledge-based methods.     

教师教学质量评估信息系统设计与实现

本文介绍了教务管理系统的一个子系统－教师教学质量评估系统的功能和实现，该系统基于校园网环境，实现教师课堂教学质量的定量评估和分析。     

A computational model of time for stiff hybrid systems applied to control synthesis

Computation has quickly become of paramount importance in the design of engineered systems, both to support their features as well as their design. Tool support for high-level modeling formalisms has endowed design specifications with executable semantics. Such specifications typically include not only discrete-time and discrete-event behavior, but also continuous-time behavior that is stiff from a numerical integration perspective. The resulting stiff hybrid dynamic systems necessitate variable-step solvers to simulate the continuous-time behavior as well as solver algorithms for the simulation of discrete-time and discrete-event behavior. The combined solvers rely on complex computer code which makes it difficult to directly solve design tasks with the executable specifications. To further leverage the executable specifications in design, this work aims to formalize the semantics of stiff hybrid dynamic systems at a declarative level by removing implementation detail and only retaining ‘what’ the computer code does and not ‘how’ it does it. A stream-based approach is adopted to formalize variable-step solver semantics and to establish a computational model of time that supports discrete-time and discrete-event behavior. The corresponding declarative formalization is amenable to computational methods and it is shown how model checking can automatically generate, or synthesize, a feedforward control strategy for a stiff hybrid dynamic system. Specifically, a stamper in a surface mount device is controlled to maintain a low acceleration of the stamped component for a prescribed minimum duration of time.     

基于人工神经网络BP算法的公司债券财务质量评级

在建立公司债券财务质量指标体系的基础上,提出了用神经网络对公司债券财务质量的综合评价方法,并利用数据进行了实证,得到了较好的评价结果。     

A virtual factory based approach to on-line simulation and scheduling for an FMS and a case study

The recent years have witnessed a revolution in computing capabilities. At the same time, modern manufacturing systems are becoming increasingly complex and capital-intensive. Here, we propose a virtual factory wherein an efficient prototyping testbed will be provided. It will be possible to develop detailed models to support system design and operation, to test different system configurations. Besides, It will be possible to manipulate all system features which impact performance, and to see the results of these manipulations, all without disrupting the actual system. This paper is one among very few that tries to represent the virtual factory in an analytic form so that many existing mathematical analyses can be applied. New pseudo resources can be added to form a new virtual environment, and control policy designed by engineers will be evaluated before being issued. Since a state-transition sequence of the virtual factory from the initial state to the final state can be seen as a schedule of the modeled system. An effective schedule of the processing can be obtained by using an A* based search algorithm, namely, Limited-Expansion A algorithm.     

Fuzzy boundary layer tuning for sliding mode systems as applied to the control of a direct drive robot

Chattering in the control signal is a significant problem in sliding mode control (SMC). The boundary layer approach is one of the many modifications proposed in the literature to avoid the chattering. In this approach, instead of the discontinuous SMC, a continuous feedback control law is employed in a boundary layer around the sliding surface. The thickness of the boundary layer is an important design parameter. This paper proposes a fuzzy online tuning method to adjust the boundary layer thickness for the best system performance without chattering. The method features the measurement of the chattering in the control signal. The paper validates the performance of the algorithm by experiments on a direct drive robot with a range of different payloads.