S.Q. Xie

Leakage current as a predictor of failure in dielectric elastomer actuators

Dielectric breakdown often leads to catastrophic failure in Dielectric Elastomer Actuator(s) (DEA). The resultant damage to the dielectric membrane renders the DEA useless for future actuation, and in extreme cases the sudden discharge of energy during breakdown can present a serious fire risk. The breakdown strength of DEA however is heavily dependent on the presence of microscopic defects in the membrane giving its overall breakdown strength inherent variability. The practical consequence is that DEA normally have to be operated far below their maximum performance in order to achieve consistent reliability. Predicting when DEA are about to suffer breakdown based on feedback will enable significant increase in effective DEA performance without sacrificing reliability. It has been previously suggested that changes in the leakage current can be a harbinger of dielectric breakdown; leakage current exhibits a sharp increase during breakdown. In this paper the relationship between electric field and leakage current is investigated for simple VHB4905-based DEA. Particular emphasis is placed on the behaviour of leakage current leading up to and during breakdown conditions. For a sample size of nine expanding dot DEA, the DEA that failed at electric fields below the maximum tested exhibited noticeably higher nominal power dissipation and a higher frequency of partial discharge events than the DEA that did not breakdown during testing. This effect could easily be seen at electric fields well below that at which the worst performing DEA failed.

Recent development on product modelling : a review

Product modelling is a pivotal activity in product development (PD) processes. Well-defined product models organize product data, production information and knowledge to satisfy the requirements of the rapid changes of the PD environment. In this paper, a comprehensive review is carried out on the recent development of product modelling technology. Four types of product modelling methodologies are discussed in detail. Two object-oriented product modelling methods: STEP-based product modelling and UML-based product modelling are reviewed and compared. The research gaps and issues are identified. To implement the product modelling into current integrated manufacturing environment, a generic product modelling framework is proposed. The future research trend of product modelling is also discussed.

A new digital watermarking scheme for 3D triangular mesh models

This paper proposes a new watermarking scheme for three-dimensional (3D) triangular mesh models. In this new scheme, feature points from the rapid changing regions are used to uniquely partition a 3D mesh model into Voronoi patches. Each Voronoi patch is then projected to a reference square plane and the corresponded range image is generated. By employing the existing two-dimensional (2D) image watermarking algorithms, watermark information is embedded into the transform domain of each range image. The watermarked 3D mesh model is obtained by perturbing the vertexes of each patch according to its watermarked range image. In order to make the watermarking scheme robust against various forms of attacks while preserving the perceptibility of the model, the length of the watermark information, the number of the feature points and the embedding strength of the watermark are made adaptive with respect to the geometry complexity of the 3D mesh models. Experimental results show that the proposed watermarking scheme has good imperceptibility and performs well under common 3D watermarking attacks such as mesh simplification, adding noise and cropping.

A case study on STEP-enabled generic product modelling framework

This research proposes a STEP-enabled generic product modelling framework (GPMF) for efficient information exchange and sharing in support of rapid product development in a modern manufacturing environment. This framework consists of four functional components: an EXPRESS data model, namely EDM; a STEP–based modelling environment; a ‘five-phase’ modelling method; and three EDM data exchange and sharing methods. The focus of this research is placed on the modelling methodologies and the definition of schemas for various product development activities such as manufacturing, inspection, etc., and the integration of the schemas with other resources defined within STEP. There are 25 schemas defined to enable that the proposed GPMF is compatible and can be used in modelling various types of products. These aspects, to our best knowledge, are not studied extensively in the literature. The structure of framework will be discussed in the paper with the focus placed on the EDM as the core of the framework. Case studies are carried out to validate the proposed GPMF. Two products are chosen from different engineering disciplines. They are modelled into product models according to the GPMF. Each case utilizes one of the EDM data exchange and sharing methods and its corresponding software environment to obtain the product models that are presented as STEP Part 21 exchange files, STEP objects and a database object. A prototype system called product data management system (PDMS) is developed to test the GPMF. The case studies show that the product models built based on the GPMF are capable of integrating information in product design, manufacturing and assembly, and the GPMF is compatible, comprehensive and flexible.

Module partition for 3D CAD assembly models: a hierarchical clustering method based on component dependencies

Reusing previous CAD assembly models directly in new product development is almost impossible in One-of-a-Kind Production (OKP) in which customer requirements vary from one to another. As such, modularisation of CAD assembly models is required to facilitate modular design for OKP. However, to the authors’ best knowledge, there has been no research carried out on modularisation of CAD assembly models so far. To bridge this gap and make the best use of existing CAD models, this paper proposes a novel module partition approach, to group existing CAD assembly models into modules based on component dependencies. In this approach, an extraction algorithm was developed to extract assembly information from a given assembly model directly, by using automated programmable interfaces of CAD software tools. The extracted information is processed to generate the component design structure matrix (DSM) representing hierarchical relations and dependency strengths between components. Four popular hierarchical clustering methods were used to work with the component DSM to produce results of module partition. A case study was carried out to illustrate the proposed methods and demonstrate their feasibility. It enables OKP companies to respond rapidly to changing customer requirements and develop customised products in a short period.

A MGrid-based information sharing system for distributed product information sharing and exchange

Grid technology is an emerging technology for the sharing of heterogeneous information globally distributed. This paper presents an information sharing system based on such a technology for a distributed injection moulding manufacturing enterprise. A Manufacturing Grid (MGrid) is proposed for information sharing in distributed manufacturing environment. Based on the MGrid, an information sharing system is developed to support the heterogeneous information sharing across departmental boundaries. By employing OGSA-DAI (Open Grid Services Architecture Data Access and Integration), the heterogeneity and the regional distribution of product information are managed efficiently. Users from different departments of the manufacturing enterprise can utilise the remote information as conveniently as they use local information for their product development tasks. A Grid portal is designed to provide uniform and friendly interfaces for users to interact with the information sharing system in a transparent manner. In order to improve the efficiency of the system, the workflow technology and the concurrently distributed information query process are also investigated in this paper. Case studies are carried out in an international injection moulding enterprise and results show the proposed system provides an efficient mechanism for the enterprise to quickly develop customised products in an economical way.

A STEP-compliant product data model for injection moulding products

In the current rapidly changing manufacturing environment, most manufacturing companies have realised that the ability to quickly develop a customised product at competitive prices is very crucial for them to survive in the keen competitive global market. Product modelling has been recognised as one of the key factors in determining the success of various product development strategies and for industrial competitiveness now and in the future. Standard for Exchange of Product model data (STEP) is an international standard designed to provide a complete, unambiguous, computer-readable definition of the physical and functional characteristic of a product through its lifecycle. This paper proposes a STEP-compliant product data model to fully support the complete product information representation and management for injection moulding product development. The data model is developed based on the structure of an injection moulding company. The entire data model consists of six data models which are defined to express information from various departments of the company. The data model is described in EXPRESS language, which can be integrated with other STEP-based product data models and databases. Consequently, the proposed system can be further extended for helping other injection moulding manufacturers to improve their product development process. An information sharing prototype system is implemented based on the proposed product data model to demonstrate the feasibility of the approach.

A WWW-based Collaborative Design and Manufacturing System for rapid mould product development

Most manufacturing companies have realized that the ability to quickly develop a customized product through an economic and efficient way is critical for them to survive in the keen competitive global market. In order to shorten the lead time to market, the product design and manufacturing requires designers and engineers from different departments of the enterprise to work together within a collaborative environment to accomplish a common mission. In this paper, a WWW-based collaborative design and manufacturing system (WCDMS) is proposed to support current product development, which enables team members in geographically distributive locations to carry out product development activities simultaneously and collaboratively. A knowledge base is developed to provide designers and engineers with complete information about the existing and the under developing products to support injection mould product development. A prototype system is presented and implemented using Web technologies and .Net programming languages to demonstrate that the proposed WCDMS system is beneficial for injection moulding manufactures to reduce the amount of reworks and shorten the product development cycle.

A novel feature points selection algorithm for 3D triangular mesh models

As an important technique of 3D (Three-dimensional) mesh model retrieval and partition, feature points are widely used to describe the intrinsic characteristics of 3D surfaces. In this paper, a novel feature points selection algorithm is proposed for 3D triangular mesh models. Detecting from the sudden variation regions of the 3D mesh models, feature points selected by our algorithm carry the significant information and possess the global geometry characteristic of the models. Experimental results show that the selected feature points are robust against attack operations on the mesh models such as mesh simplification and adding noise.

STEP-Compliant Knowledgebase in Support of Customized Product Development for SMEs

Nowadays, Small and medium-sized Manufacturing Enterprises (SMEs) are facing intensive competition from the global market. For these SMEs, how to better manage and record the previous Product Development (PD) knowledge has become a core issue for them to improve PD process, cut down development cost and reduce lead time. In this paper, we present our work in developing a STEP (Standard for the Exchange Product Model Data)-compliant knowledgebase for the development of customized products. The paper focuses on how to develop a STEP-compliant knowledgebase that is applicable to different types of customized products. This knowledgebase uses the STEP as a foundation. Tools are developed to model, record and search information such as customer requirements and expectations, engineering responses, product design, decision making and product machining processes, etc. The recorded product information and knowledge in the knowledgebase will then be reused for the development of customized products of similar types.