H.H. Cheung

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.

A multi-material virtual prototyping system

Abstract This paper proposes a multi-material virtual prototyping system for digital fabrication of heterogeneous prototypes. It consists mainly of a topological hierarchy-sorting algorithm for processing slice contours, and a virtual simulation system for visualisation and optimisation of multi-material layered manufacturing (MMLM) processes. The topological hierarchy-sorting algorithm processes the hierarchy relationship of complex slice contours. It builds a parent-and-child list that defines the containment relationship of the slice contours, and subsequently arranges the contours in an appropriate sequence, which facilitates toolpath planning for MMLM by avoiding redundant tool movements. The virtual simulation system simulates MMLM processes and provides stereoscopic visualisation of the resulting multi-material prototypes for quality analysis and optimisation of the processes.

Implementation issues in RFID-based anti-counterfeiting systems

RFID has emerged as a potential tool to combat product counterfeiting, which undermines the global economy hugely. Recently, a number of anti-counterfeiting approaches have been proposed for such purpose. This paper presents a track-and-trace system for RFID-based anti-counterfeiting, and addresses possible implementation issues, such as tag selection, product tagging, tag programming and locking. A packaging line for bottled products is developed and integrated with the proposed system for investigation of these issues. Experiments are conducted to determine the critical tag moving speed beyond which the tag programming rate or reliability of tagged products being transferred on a convey drops significantly. The critical tag moving speed is vital not only for determining the maximum production throughput possible, but also for setting up RFID equipment needed to ensure tagged products with erroneous tagging can be sorted out from the packaging line accordingly.

A topological hierarchy-based approach to toolpath planning for multi-material layered manufacturing

This paper proposes a topological hierarchy-based approach to toolpath planning for multi-material layered manufacturing (MMLM) of heterogeneous prototypes. The approach facilitates control of MMLM and increases the fabrication efficiency of complex objects by generating multi-toolpaths that avoid redundant tool movements and potential collisions. It uses a topological hierarchy-sorting algorithm to group complex multi-material slice contours into families connected by a parent-and-child relationship. Subsequently, a sequential toolpath planning algorithm generates multi-toolpaths for sequential deposition of materials without redundant tool movements. To reduce build time further, a concurrent toolpath planning algorithm generates collision-free multi-toolpaths to control the tools that deposit materials concurrently. It uses parametric polygons to construct tool envelopes for contour families of the same material property to simplify detection of tool collisions. The tightness of polygons can be controlled to suit the processing speed and the optimality of the resulting concurrent toolpaths. The proposed approach has been implemented as an integral part of a multi-material virtual prototyping (MMVP) system that can process complex slice contours for planning, stereoscopic simulation, and validation of multi-toolpaths. It may be adapted for subsequent control of MMLM processes.

RFID tag data processing in manufacturing for track-and-trace anti-counterfeiting

We address the issues in e-pedigree management for RFID-based track-and-trace anti-counterfeiting.We propose an algorithm for RFID tag data processing and synchronization (TDPS) to generate initial e-pedigree for apparel products during production.We identify and study tag EPC writing as a major bottleneck of e-pedigree generation.We incorporate an integrated method for EPC block writing and verification to optimise the TDPS algorithm for practical implementation in packaging lines. With advancement in radio frequency identification (RFID), RFID-based track-and-trace anti-counterfeiting has attracted considerable research interests. Track-and-trace anti-counterfeiting demands a trustworthy electronic pedigree (e-pedigree), which records the movements of product items from manufacturers to retailers, to ensure high supply chain visibility and to provide evidence for product authentication. Creation and synchronization of initial e-pedigrees in the manufacturing stage is particularly crucial to the accuracy and trustworthiness of subsequent processing of the e-pedigrees and authentication of product items. This is a critical yet challenging task, as it involves a number of practical issues, such as incomplete tag writing/locking, environment disturbances, and potential data falsification. This paper first presents an innovative track-and-trace anti-counterfeiting system, and then proposes a tag data processing and synchronization (TDPS) algorithm to generate initial e-pedigrees for general, tangible products during production. An RFID-enabled apparel packaging line is established to validate the performance of TDPS and identify the bottleneck of e-pedigree generation. Experiment results show that TDPS can create accurate and secure initial e-pedigrees for fast moving product items, and that tag EPC writing is a major bottleneck of e-pedigree generation. Thus, we optimise TDPS by incorporating a block writing method and an integrated verification step to remove the bottleneck. Further experiments demonstrate the optimised TDPS can be adapted to suit different practical requirements to achieve a good balance between tag writing/locking rate and the moving speed of product items in packaging lines without severing the throughput.

A topological hierarchy-based approach to layered manufacturing of functionally graded multi-material objects

This paper presents an approach based on topological hierarchy to representation and subsequent fabrication of functionally graded multi-material (FGM) objects by layered manufacturing. The approach represents an FGM object by material control functions and discretisation of slice contours. Based on the topological hierarchy of slice contours, material control functions are associated with contour families of some representative layers across the X-Y plane and along the Z-plane. The material composition at any location is calculated from the control functions, and the slice contours are discretised into sub-regions of constant material composition. The discretisation resolution can be varied to suit display and fabrication requirements. In comparison with pixel- or voxel-based representation schemes, this approach is computationally efficient, requires little memory, and facilitates fabrication of large and complex objects, which can be assemblies of FGM and discrete materials. The proposed approach has been incorporated with a virtual prototyping system to provide a practical and effective tool for processing FGM objects.

Multi-material virtual prototyping for product development and biomedical engineering

This paper describes the development of a multi-material virtual prototyping (MMVP) system, which integrates virtual reality (VR) and layered manufacturing (LM) for digital fabrication of multi-material prototypes to facilitate advanced product development and biomedical engineering. The MMVP system incorporates a topological hierarchy-sorting algorithm, two algorithms for sequential and concurrent multi-toolpath planning, a build-time estimation algorithm, and a virtual prototyping system. Based on the topological hierarchy of slice contours, the sequential multi-toolpath planning algorithm generates sequential toolpaths that avoid redundant tool movements, while the concurrent multi-toolpath planning algorithm generates collision-free concurrent toolpaths to further reduce the build-time. To verify the resulting toolpaths and to facilitate estimation of fabrication cost, a mathematical model is incorporated for build-time estimation of multi-material fused deposition processes. The MMVP system is useful for planning, stereoscopic simulation, build-time estimation and validation of multi-toolpaths, and subsequent digital fabrication and analysis of multi-material prototypes.

A CAVE-based Multi-Material Virtual Prototyping System

This paper proposes a CAVE-based multi-material virtual prototyping (CMMVP) system for immersive stereoscopic visualisation and optimisation of multi-material layered manufacturing (MMLM) processes. The CMMVP system consists mainly of a suite of software packages for simulation of MMLM processes, integrated with a multi-screen CAVE-based virtual reality (VR) system, to create an immersive virtual environment for digital fabrication of multi-material product prototypes. In comparison with desktop-based or semi-immersive VR systems, the CMMVP system blocks out environmental disturbances such that designers can fully immerse in performing stereoscopic visualisation and quality analysis of the resulting multi-material prototypes for subsequent improvements of a product design. The CMMVP system facilitates advanced product design and helps reduce product development time and cost substantially.

Item-level RFID for enhancement of customer shopping experience in apparel retail

We use item-level RFID to enhance customer shopping experience in apparel retail.We install RFID devices to collect customer shopping behaviour.We implement intelligent fuzzy screening algorithms to analyze customer preferences.We use the results for apparel collocations to improve marketing and services. In the customer-oriented apparel retail industry, providing satisfactory shopping experience for customers is a vital differentiator. However, traditional stores generally cannot fully satisfy customer needs because of difficulties in locating target products, out-of-stocks, a lack of professional assistance for product selection, and long waiting for payments. Therefore, this paper proposes an item-level RFID-enabled retail store management system for relatively high-end apparel products to provide customers with more leisure, interaction for product information, and automatic apparel collocation to promote sales during shopping. In this system, RFID hardware devices are installed to capture customer shopping behaviour and preferences, which would be especially useful for business decision-making and proactive individual marketing to enhance retail business. Intelligent fuzzy screening algorithms are then developed to promote apparel collocation based on the customer preferences, the design features of products, and the sales history accumulated in the database. It is expected that the proposed system, when fully implemented, can help promote retail business by enriching customers with intelligent and personalized services, and thus enhance the overall shopping experience.

Data management of RFID-based track-and-trace anti-counterfeiting in apparel supply chain

With recent advancement in Radio Frequency Identification (RFID), RFID-based track-and-trace anti-counterfeiting has attracted considerable research interests. A track-and-trace anti-counterfeiting system requires an integral and reliable electronic pedigree (e-pedigree) to ensure high product visibility along the supply chain. With the continuous movements of large volumes of products along the supply chain, huge amounts of RFID data would be inevitably generated, posing great challenges to system development and operation. As such, the front-end RFID data should be well-formatted for efficient capturing, filtering, and synchronization in a logical and reliable way, so that the accumulated e-pedigree would be complete and trustworthy for subsequent product authentication. In this paper, we present an innovative track-and-trace anti-counterfeiting system for apparel products, and discuss a number of key data management issues, such as e-pedigree formatting, data synchronization, and traceability / visibility control. A data format of e-pedigree for full traceability of garments is proposed to support products authentication in item-level, products anti-lost in pallet-level and products status prediction in batch-level. Based on this format, a three-step mechanism of data synchronization is established to ensure e-pedigree integrity. To avoid possible leakage/falsification of e-pedigree data, an RBAC-based access control is proposed as an auxiliary module of the anti-counterfeiting system.