Literature Review and Research Objectives

This study describes the application of the develop ed model to the scheduling of the Robotic Flexible Assembly Cells (RFACs). The present study is a continuation of the paper titled “Development of a Fuzz ySimulation Model of Scheduling Robotic Flexible Assembly Cells”. This new model for multi-objective scheduling problems in RFACs was based on combining a fuzzy-based mathematical model with simulation software tools. In this study, a hypothetical case study of RFACs is presented to demonstrate the effectiveness of the developed model and then compare the results that are obtained by the new methodology with the common scheduling rules. The simulation results show that the performance of the proposed methodology outperforms the most popular scheduling rules from previous research.

Multi-objective optimisation of dynamic scheduling in robotic flexible assembly cells via fuzzy-based Taguchi approach

• A new control logic for the SCMSHPD system under low meteorological conditions was proposed. • Performance of the SCMSHPD system operating under the new control logic were analyzed. • The effects of the waste heat recovery on the combined drying system under different meteorological parameters were obtained. • Drying process of the combined drying system was optimized. To solve the problem that the high drying temperature demand could not be met when combined drying system operated under low ambient temperature and weak solar irradiance, a new control logic of the solar combined multi-heat source heat pump drying (SCMSHPD) system was proposed and its simulation model was established. By modifying its operating strategy, the SCMSHPD system achieved a higher drying temperature under low environment temperature and weak irradiance, which ensured the implementation of the drying process. The simulation results was verified through experimental study. Additionally, to address the issue of significant heat loss of the exhaust air, waste heat recovery was implemented and its impact on the system’s operating characteristics was analyzed. At last, the drying process was optimized due to the significant improvement of the specific moisture extraction rate ( SMER ) and the system performance was further improved. The results showed that the errors in coefficient of performance ( COP ), energy consumption, and SMER between the experimental and simulation results were 4.04%, 1.84% and 1.53% respectively, which verified the reliability of the simulation model. In October, the COP of the SCMSHPD system without waste heat recovery was 3.66% higher than that of the ASHPD system, but with the decrease of ambient temperature and solar irradiance, the COP of the combined drying system increased by 5.86% in December, demonstrating the advantage of the SCMSHPD system with the new control logic under low meteorological parameters. The waste heat recovery could not improve the system performance of the SCMSHPD system operating with the new control logic proposed, which caused a decrease of 1.06% and 1.19% in October and December respectively. However, the SMER was significantly increased by 70.67% and 12.78% respectively, and the energy consumption was significantly decreased by 41.33% and 10.94%. The results indicated that although waste heat recovery resulted in a slight decrease in system COP , the significant reduction in energy consumption and notable increase in SMER demonstrated a marked improvement in the overall system performance. Due to the significant increase of the SMER , the drying time was shortened, which caused an increase of 1.77% in COP in October. With meteorological parameters became lower, the COP get a bigger increase of 3.34%. Therefore, it could be concluded that the combination of waste heat recovery and shortened drying time could effectively improve the system performance, and the lower the meteorological parameters, the greater the improvement in the system performance. This study can provide important guidance for the selection of control logic and the optimization of the drying process for the SCMSHPD system under low meteorological parameters.

Companies are increasingly being forced by market demands to increase the competitiveness of their products in regard to price, quality and delivery time. Development, both of product and production, is the key word in achieving this goal. This paper focuses on the following related subject: cost-effective design, with applications to robotic assembly cells. Against this background, a total productivity model is introduced, which allows an opinion to be formed about the performance of robotic assembly cells during the conceptual stage of the design process.

This book focuses on the design of Robotic Flexible Assembly Cell (RFAC) with multi-robots. Its main contribution consists of a new effective strategy for scheduling RFAC in a multi-product assembly environment, in which dynamic status and multi-objective optimization problems occur. The developed strategy, which is based on a combination of advanced solution approaches such as simulation, fuzzy logic, system modeling and the Taguchi optimization method, fills an important knowledge gap in the current literature and paves the way for future research towards the goal of employing flexible assembly systems as effectively as possible despite the complexity of their scheduling.

Current developments in the field of automated assembly systems show an increasing interest in systems that are flexible in both CAD based product design and CAD based assembly. For the application addressed in this paper, coupling the vision system and a CAD database is of prime importance in order to achieve the required automatic reconfiguration of the assembly cell when new parts are defined. This paper presents a 3D CAD-based vision system for obtaining 3D data about the scene. After the images are acquired, edge detection is preformed and the detected edges are stored as chaincodes. Following that, a stereo vision algorithm is applied for finding the recognition features. The output are lists of features that are combined into a 3D wireframe representing the scene. The recognition algorithm takes the observed wireframe outputs from the stereo vision system, and compares them with a set of model wireframes derived from previous models, in order to select the 'best match', where the previous models used for recognition are derived from a product data model (PDM). The PDM is an interface between the CAD database and the recognition system, which allows the automatic generation of new models when new parts are introduced into the system. The vision system described in this paper is part of an intelligent robotic assembly cell, where the aim is to build a flexible intelligent robotic assembly cell, such that robots would be able to automatically assemble a random variety of small- batch products.

Flexible Assembly Systems - Hardware Components and Features: Basic components of a FAS.- Classification of flexible assembly systems.- Examples of industrial installations.- Issues in Design, Planning and Scheduling of Flexible Assembly: FAS design issues.- Network design for material flow systems.- Design for assembly.- Assembly planning.- Planning and scheduling.- Loading and Routing Decisions in Flexible Assembly Systems: Description of a flexible assembly system.- Optimization of station workloads and product movements.- Design and balancing of flexible assembly lines.- Numerical examples.- Simultaneous loading and routing.- Sequential loading and routing.- Loading and Routing Decisions with Assembly Plan Selection: Simultaneous loading, routing and assembly plan selection in a general flexible assembly system.- Simultaneous loading, routing and assembly plan selection in a flexible assembly line.- Loading and Scheduling in Flexible Assembly Cells: Loading and scheduling in a robot assembly cell.- Loading and sequencing in printed circuit board assembly.- Production Scheduling in Flexible Assembly Lines: Flexible assembly line with limited intermediate buffers.- Flexible assembly line with no in-process buffers.- Global lower bounds for flexible flow lines with unlimited buffers.- Just-in-time scheduling of flexible assembly lines.- Multilevel scheduling of flexible assembly lines with limited intermediate buffers.- Machine and Vehicle Scheduling in Flexible Assembly Systems: Dispatching scheduling.- Machine and vehicle scheduling - a multi-level approach.- Machine and vehicle scheduling - a single-level approach.

Urban floods have adverse impacts on the performance of urban infrastructures and the life of residents. The floods cause heavy damages and perturbation in the serviceability of urban infrastructures as well as transportation. Therefore, different factors affecting the urban water flood characteristics should be considered in urban development planning, especially in metropolitan areas. In recent years, climate change and its consequences have affected the total components of the water cycle as well as floods. These effects are intensified in urban areas because of the anthropogenic effects they have on the water cycle, such as reducing the infiltration capacity of basins, construction regardless of the channel's right of way, and disposal of sediment and solid wastes into channels that will decrease the channels' safe carrying capacity. In this way, incorporating climate change impact on urban water studies could help to achieve more reliable results to be applied in real-time planning of urban areas through selection of best management practices (BMPs). In this study, an algorithm for selecting the BMPs to improve the system performance and reliability in dealing with urban flash floods is proposed that considers the anthropogenic and climate change effects. The suggested algorithm is applied to the Tehran metropolitan area drainage system as a case study. First, the future rainfall pattern of the study area under climate change impact is simulated. Then, the effectiveness of present and future development projects for improvement of drainage system performance is evaluated under different scenarios. Also, the effect of solid wastes and sediments carried with surface runoff in system performance is considered. Finally, feasibility of suggested BMPs and their effectiveness in urban flood management as well as their related costs and benefits are considered. The results of the study show the significance of using analytical and management tools in assessing and improving the urban drainage system.

Industrial automation and safety applications demand low latency and ultra reliable communication. Currently deployed wireless communication technologies are mostly developed for non-critical applications and hence, they are not suitable for these kind of applications. On the other hand, cable based communication is widely popular in industries, even though it has limitations towards cost of installment and is susceptible towards mechanical wear and tear. This paper reviews the feasibility of large antenna arrays at the receiver to achieve low latency and ultra reliable communication for up-link scenarios. The suitability of both coherent and non-coherent multiple input multiple output (MIMO) receivers are investigated. Non-coherent MIMO receiver is found to be a promising option as signal to noise power ratio (SNR) is fairly reasonable in achieving the desired reliability. The effect of antenna correlation at the transmitter and at receiver on reliability are also looked into. Its influence on the system performance is very nominal. Moreover, in certain scenarios, antenna correlation at the transmitter gives a significant improvement in system performance. Furthermore, having a single antenna at the sensors is found not to be a limiting factor in achieving the desired performance goal.

This study describes the application of the developed approach to the scheduling of the Robotic Flexible Assembly Cells (RFACs). The present study is a continuation of the paper titled "development of fuzzy AHP and TOPSIS approach for multi-objective scheduling problems in robotic flexible assembly cells". In this paper, a realistic case study of RFACs is presented to examined and verified the developed approach via implement three phases: problem description; application of FAHP-FTOPSIS; and analysis of the results. The analysis showed the stability of the results for FAHP-FTOPSIS and also verified the robustness and the appropriateness of the proposed approach. This study also demonstrated that the proposed approach can be successfully used in the multi-objective optimisation of dynamic scheduling in RFAC.

Hierarchical femtocell architectures have become popular recently because of their potential to provide increased coverage and capacity in cellular systems. However, introduction of femtocells might reduce the overlay macrocell system performance due to increased interference caused to macrocel-lular users. With MIMO precoding, the Least Interference (LI) technique can be employed at the femtocellular base stations (FBSs) to minimize the interference to the macrocellular user. This approach maximizes the macrocellular throughput, but also results in significant reduction in femtocellular throughput. As is well-known, a Precoding Matrix Index (PMI) approach to beamforming can maximize the signal power at a desired receiver, with minimal feedback. In this paper, we apply mode adaptation between LI and PMI at the FBSs in order to increase both the macrocellular and femtocellular throughputs. We show that allowing for mode adaptation at each FBS improves the system performance when compared with using the same mode across the system, and a simple binary choice at each FBS can nearly achieve the optimum mode-adaptation performance. Analysis and simulation results in a multicell environment are presented to illustrate the improvement in system performance with the proposed techniques.

In this paper, we propose a fast and simple system emulator, called a system performance emulator (SPE), to evaluate long read operations. The SPE estimates how much system-wide performance is enhanced by using a faster solid state disk (SSD). By suspending a CPU for a certain time during direct memory access (DMA) transfer and subtracting this suspended time from the total DMA time, the SPE estimates the improvement in system performance expected from an enhanced SSD prior to its manufacture. We also examine the relation between storage performance and system performance using the SPE.

Using MATLAB to model and simulate a photovoltaic system to produce hydrogen

The near-far problem and the correlations in a MIMO channel are two major obstacles in the way of widely implementing space division multiple access (SDMA) systems. In this paper we investigate the effect of distributing the basestation antennas and the reduction of intra-user correlations on the performance of a MIMO-OFDM system in which a basestation, composed of distributed antenna arrays, is communicating (downlink transmission) with several single antenna mobile users. The arrays are located at different sites in a Ricean-Lognormal channel environment. Very significant improvement in system performance is achieved due to the improved spatial properties of the MIMO channel and due to the reduction of channel matrix correlations

The introduction of many VLSI devices into system designs is placing new requirements on the packaging technologies that are used to interconnect devices and assemble systems. These requirements include the assembly of high pin out (up to 500 I/O's) devices, the ability to sustain synchronous system operation at frequencies up to 100 MHz, and cooling at thermal loads greater than 1 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A new packaging technology is described that will overcome many of the limitations of conventional packaging. The new technology has the capability for assembling devices with more than 200 I/O's, a maximum signal lead length less than 20 cm, a power and ground lead inductance less than 0.1 nH, a signal lead capacitance less than 20 pF, and a cooling capability greater than 1 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The substrate for the proposed new packaging technology is a silicon wafer. The power and ground are distributed by means of copper planes on either side of the substrate. Two signal layers are positioned above the power plane using a polyimide dielectric material. The signal leads are a minimum of 10 µm wide. With 10-µm-thick polymer, the line capacitance is ~ 1 pF/cm. Copper metallization is · used to achieve a resistance of 10 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Omega</tex> /cm for the minimum width signal leads with 2-µm-thick conductors. Devices are attached to the interconnection substrate by means of solder. The solder technology was chosen because it is repairable, provides a low-inductance (< 1 nH) connection between chip and substrate, and enables I/O pads to be positioned over the area of the chip. The matched thermal expansion coefficient between the substrate and chip results in a mechanically stable solder attachment. This new packaging technology has been demonstrated by means of a prototype vehicle. Three chips from the WE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> 32100 chip set: CPU, memory management unit (MMU), and math accelerator unit (MAU), have been flip-chip bonded and interconnected together on a 1.3 x 3.0-cm substrate. The chips have been spaced 500 µm apart. The assembly has been bonded to a metal heat sink using a compliant adhesive layer to minimize stresses in the silicon substrate. The chip-to-heat sink thermal resistance for the assembly is 5°C/W (junction to case). A 160 I/O multilayer printed wiring board package has been used to fan out from the edge of the substrate to pins on a 100-mil grid. Wire bonds electrically connect the substrate to the package and provide for chip backside grounding. A protective cover completes the package assembly. In summary, significant improvements in system performance can be achieved with the new multichip technology. Compared to conventional packaging, a factor of 3 improvement in system operating frequency is expected when IC's are designed specifically for the technology. Additionally, system size and power dissipation can be reduced by a factor of seven and 30 percent, respectively.