KEYWORDS: Signal processing, Signal detection, Process control, Wavelet transforms, Wavelets, Manufacturing, Pattern recognition, Sensors, Data storage, Data modeling
Manufacturing processes are generally monitored by observing uniformly sampled process signals collected from
application specific sensors. Effective process monitoring and control requires identification of different types of
variations, including recurring patterns, in process variables. From the process control view point, any repeating patterns
in the process measurements will warrant an investigation into potentially assignable causes. In order to devise an
effective process control scheme, a novel method for identifying the repeated occurrence of patterns in process
measurements is described in this paper. First the sampled process signal is decomposed into signals of different
resolution using a wavelet transform. Next, a frequency index is assigned to every sampling point of the process signal at
every resolution level to improve the pattern recognition. Recurring patterns are first detected at different resolutions and
are then integrated to arrive at the final results. The experimental results show that the method used in this work
accurately detects a broader family of recurring patterns even in the presence of noise.
Location-awareness is a key enabler for using energy-conserving protocols and other location-based services in Wireless Sensor Networks (WSN). Due to the ad hoc nature of WSN, and resource-constrained sensor nodes, the localization technique must be infrastructure-free, computationally simple, and energy-efficient. In this paper we present an ad hoc localization technique that satisfies these requirements. The proposed localization technique is infrastructure-free, anchor-free, and is computationally efficient with reduced communication. We use a novel combination of TOA/TDOA and AOA ranging techniques to detect and estimate ranges between neighbors. Using this information we construct unidirectional coordinate systems to avoid the reflection ambiguity. This reduces the amount of information, and thus communication, required to induce location-awareness in sensor nodes. We then compute node positions using a transformation matrix [T] which reduces the computational complexity of the localization algorithm while computing positions relative to the fixed coordinate system.
This research investigates the advantages offered by embedded sensors for cost-effective and environmentally benign product life cycle management for desktop computers. During their use by customers as well as at the end of their lives, Sensor Embedded Computers (SECs) by virtue of sensors embedded in them generate data and information pertaining to the conditions and remaining lives of important components such as hard-drive, motherboard, and power supply unit. A computer monitoring framework is proposed to provide more customer comfort, reduce repair costs and increase the effectiveness of current disassembly practices. The framework consists of SECs, remote monitoring center (RMC), repair/service, disassembly, and disposal centers. The RMC collects dynamic data/information generated by sensors during computer usage as well as static data/information from the original equipment manufacturers (OEMs). The RMC forwards this data/information to the repair/service, disassembly, and disposal centers on need-basis. The knowledge about the condition and remaining life of computer components can be advantageously used for planning repair/service and disassembly operations as well as for building refurbished computers with known expected lives. Simulation model of the framework is built and is evaluated in terms of the following performance measures: average downtime of a computer, average repair/service cost of a computer, average disassembly cost of a computer, and average life cycle cost of a computer. Test results show that embedding sensors in computers provides a definite advantage over conventional computers in terms of the performance measures.
The driving forces behind product take-back and green manufacturing are well established. The two main product end-of-life options are reuse/remanufacturing and recycling. For either option, all take-back units are treated equally because no information that tracks the conditions of a product during its useful life is available. For example, all expired PCs are treated equally; no distinction can be made about which units still have healthy hard disks. This paper discusses sensor-based monitoring and prognostic methodologies for tracking the condition of products while being used by customers and timely and targeted servicing, smart and selective disassembling and refurbishing of products with known (long) remaining lives. The paper also discusses the added benefits to product manufacturers when the time comes to redesign their products. The real-time field data on service and utilization of products are communicated to manufacturers’ headquarters for further analysis.
This paper develops a computational methodology that allows decision-makers to calculate the disassembly cost of a product before it is built. The methodology makes it simple to perform "what if" scenarios fairly quickly. A Java based application has been developed to implement this methodology and it uses computational algorithms and a graphical user interface to enable designers to simulate product designs. The front end user interface is a Java based application while the back-end is the combination of a data parser and disassembly engine, which also makes use of Java and XML technologies. The disassembly engine performs calculations based on data represented in an XML data store and runs as the back-end component of the computational tools. The user interface has the ability to display a dynamically configurable disassembly tree. The disassembly knowledge is represented in XML format to allow robust and scalable parsing and processing of the various disassembly alternatives that correspond to the configurable disassembly tree. Examples are presented to demonstrate the implementation and capabilities of the computational design methodology presented in this paper.
Environmentally conscious manufacturing is an important paradigm in today's engineering practice. Disassembly is a crucial factor in implementing this paradigm. Disassembly allows the reuse and recycling of parts and products that reach their death after their life cycle ends. There are many questions that must be answered before a disassembly decision can be reached. The most important question is economical. The cost of disassembly versus the cost of scrapping a product is always considered. This paper develops a computational tool that allows decision-makers to calculate the disassembly cost of a product. The tool makes it simple to perform 'what if' scenarios fairly quickly. The tool is Web based and has two main parts. The front-end part is a Web page and runs on the client side in a Web browser, while the back-end part is a disassembly engine (servlet) that has disassembly knowledge and costing algorithms and runs on the server side. The tool is based on the client/server model that is pervasively utilized throughout the World Wide Web. An example is used to demonstrate the implementation and capabilities of the tool.
This paper presents a framework for a collaboration platform that facilitates agile design process. The paper specifies the drivers for building such a collaboration platform, identifies its attributes, and proposes the mechanisms for resolving its dilemmas. The primary force that is driving agile product design is the market demand for the 'right products,' which have three attributes: (1) right features, (2) right time to market, and (3) right cost. The success of a company in marketplace is decided by how well it strikes a balance between these three attributes while developing new products. There have been several productivity boosting techniques such as CAD, CAM, CAE tools to assist designers at each stage of product development. However, the total product development process has not benefitted much from them, because of the inherent delays between the stages that account for 30 to 90 percent of the total product development time. An innovative approach, which employs web- based collaboration tools, can offer dramatic improvements in the process of introducing 'right products' into the market. The paper contends that an ideal collaboration platform should enable any designer located anywhere to design products using any CAD and any PDM on any platform. Such a collaboration platform potentially (1) reduces product development time, (2) curtails product development cost, and (3) improves the chances for first to market.
This paper presents a new technique which uses a tree for constraining the compatibility among components in a logical bill of material (BOM) structure. The new representation for restricting possible combinations of components is designed to address the limitations of matrix representations that were used for the same purpose in earlier work. These matrix representations, which assume that the compatibility in a BOM can always be described for pairs of components, cannot be used for products in which the compatibility among three or more components is an issue. Thus, it is proposed to use a standard tree with a special representation, which is called a trie, to represent the compatibility between the components in a product configuration. Similar to the inter-component compatibility matrix, the trie can be used to validate and/or complete an arbitrary product configuration during the configuration process without having to spell out product configuration rules. The new representation provides the user with a means to describe all possible compatibility relationships with a limited amount of data. This trie representation is comprehensive, easy to maintain, and easy to understand.
This paper presents a new approach to address the problem of Planning for Disassembly (PFD). The approach is based on the Case-based reasoning technique. To assist planners to solve PH) problems, a system must have some heuristics and domain specific knowledge, which is related to the representation of the disassembly knowledge. In previous work, the authors suggested to use EMOPs (Eposodic Memory Organization Packet) for the knowledge representation of the PFD plan. This paper demonstrates the implementation of the EMOP memory model. The model has been implemented in C++, and tested. An example is presented to demonstrate the capabilities of the memory model.
Extensible markup language (XML) is a new powerful technique for Web and Internet development. It is a method of defining structured data in a text file. XML is expected to do for data what HTML has done for Web pages. XML's stiength lies in its simplicity to represent data and knowledge. It can maintain hierarchical structures encountered in many systems including assemblies and disassemblies. It can also be well integrated with Java, and its Java beans. Its strength lies in its flexibility to adapt to any knowledge domain because it is a metalanguage. It is used to develop modeling languages that are tailored to specific knowledge, and specific data structures and hierarchies. This paper presents an overview of XML, followed by a proposal of an XML-based knowledge representation model for disassembly planning. An example is used to demonstrate the capabilities ofthe proposed XML model.
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