Consumption of silk

Automatic assembly equipment is the key to improving the efficiency and quality of workpiece assembly. The precision of assembly directly influences the overall quality of the assembled product. To optimise the position control accuracy in the automatic assembly equipment, a variable universe fuzzy proportional integral (VUFPI) controller optimised by the sparrow search algorithm (SSA) is developed in this paper. The developed controller adopts the SSA to adjust in real time the universe of the fuzzy controller according to the deviation of the servo system. The servo system model is established to evaluate the performance of the proposed SSA-VUFPI controller; furthermore, the SSA-VUFPI controller is implemented in the automatic assembly equipment for experimental evaluation. The analysis results demonstrate that the proposed SSA-VUFPI controller is capable of improving the anti-interference ability and position accuracy of the servo system compared to traditional PI, VUFPI, and currently used back propagation neural network proportional-integral-derivative (BP-PID), fractional-order PID (FOPID), and SSA-PID controllers. Moreover, it effectively improves the position accuracy of the workpiece and ultimately improves the quality of the assembly.

Screw assemblies of radar are characterized by numerous densely distributed small screws of various types, rendering their manual assembly difficult and inefficient. To improve the assembly quality and efficiency, an automatic assembly system was developed. First, the position and attitude relationships among the workpiece, camera, and base coordinate systems of the manipulator were obtained using three-point location and nine-point calibration methods. Second, a visual servoing strategy is designed for guiding the manipulator such that its position can be adjusted adaptively to achieve the high-precision positioning of threaded holes. Third, a method for evaluating assembly quality is developed. The templates of angle–torque curves of various screws were produced by fitting experimental data. Furthermore, the assembly quality was determined by calculating the similarity between the angle–torque curves and templates based on the Fréchet distance. Finally, the feasibility was verified using a flat plate component with five threaded holes.

Mass personalization and shorter product life cycles complicate the assembly of manufacturing companies. To handle the complexity, a high number of employees execute varying assembly tasks. Their work is characterized by learning new tasks frequently to produce different variants. To achieve good learning results in a short amount of time, a suitable individual assembly workers’ competence development process is crucial. Therefore, this publication shows the development of a user methodology to plan the competence development process focusing on selecting learning measures that fit both the work situation and learning employees. The presented user methodology is based on a standardized description and selection procedure for learning measures by using results of a Domain Mapping Matrix, Delphi study, and expert interviews. The publication contributes to improved competence development to support the strategic empowerment of the workforce and to increase the flexibility in manual assembly.

Today, importance of flexibility and reconfigurability needs to be addressed when designing and implementing a cost-effective and responsive manufacturing system. Such a system should be able to accommodate dynamic changes of product varieties and production volumes by maximizing its production capability and minimizing its production costs, this is particularly useful for a SME (small and medium-sized enterprises) to remain competitive in the market. For a manual assembly line, it is always a good practice using a highly skilled workforce that each assembly worker is capable of performing multiple tasks. Ideally, each worker is fully trained to complete assigned tasks of a unit from start to finish. This paper presents a case study of incorporating 5S management rules into an assembly system using so-called skillful and dynamic walking workers as a combination of lean management approaches to improve productivity and efficiency of a shop floor production line at a local plant.

Prediction of Defect Propensity for the Manual Assembly of Automotive Electrical Connectors

Currently, the realization of rationally designed architectures based on polyoxometalates (POMs) with designed functions has mostly been achieved through the preparation of functional films. However, the traditional approaches suffer from the drawbacks such as time-consuming processes, ill-defined structure and quality, random orientation of the POM molecules, and unsatisfactory performance. In this study, microcrystals of Ag9[EuW10O36]·36H2O (denoted as Ag9[EuW10O36]) were synthesized via a titration method by treating Na9[EuW10O36]·32H2O (denoted as Na9[EuW10O36]), selected as a prototype, with Ag+, leading to the formation of a water-insoluble crystalline powder with a uniform hexagonal platelet morphology. After this, a simple yet efficient manual assembly method was used to rapidly manufacture Ag9EuW10O36 microcrystal thin films on a glass substrate with high coverage, high crystallinity, and highly preferential orientation. Note that the as-prepared films emit orange polarized fluorescence with an anisotropy value of about 0.21, which places them among the materials of largest anisotropy. It is expected that the manual assembly approach can be generally adopted for the fabrication of many other kinds of polyoxometalate-based materials on various substrates for practical applications.

The Hardware-In-the-Loop (HIL) simulation system for on-orbit docking dynamics is a large-scale complex test equipment. It establishes working conditions for the docking mechanism similar with those on orbit. The kernel of above dynamics HIL simulation system is a mechanical force and movement actions simulator. Besides the mechanical force and movement actions simulator, it also includes an environmental simulator, a microgravity simulator and so on. In a narrow mind, the HIL simulation system for on-orbit docking dynamics refers to the mechanical force and movement action simulator. It is a feedback system which consists of the dynamics simulation model and real-time simulaton computer, the hardwares under test, the force and torque sensor, the motion simulator. The research topic of this paper is limited in above narrow mind. The HIL simulation system for on-orbit docking dynamics is a key technology that played important roles in the lunar excursion of America and in the assembling and re-supplying of Russian MIR space station. Morden space programme enhance the requirements to the HIL simulation for spacecraft docking dynamics. International Space Station (ISS) program also required that the ISS Common Berthing Mechanism (CBM) testing on ground simulator should be performed under operational vacuum and thermal conditions (Office of NRBMP, 1999). In the early days, the physical simulators played main roles in docking dyniamics tests. Because of the development of computor and the complexity of modern docking mechanism, the HIL simulation technology is applied in the docking dynamics simulation. The dynamic docking test system (DDTS) is setup in US (Gates & Graves, 1974), and the integated testing system for docking mechanism was built in former Soviet (Peng et al., 1992). In1980s, docking dynamic test facility (DDTF) was created for testing the handleslatch docking mechanism (Crimbert & Marchal, 1987). National space development agency of Japan built the rendezvous and docking operation test system (RDOTS) testing threepoints handles-latch docking mechanism (Lange & Martin, 2002). The HIL simulation for spacecraft on-orbit docking is a attractive and promising research field. Lim et al. (1989) modeled and simulated the Stewart platform of DDTS. They pointed

De novo genome assembly is a fundamental problem in genomics research. When assembling large genomes, time is often a very important concern, and one might have no choice but to use a more efficient assembler like SOAPden-ovo2 instead of a high-quality but prohibitively slow assembler (e.g., SPAdes). Yet SOAPdenovo2 has inherent difficulty to utilize the full advantage of longer reads (say, 150bp to 250bp from Illumina HiSeq and MiSeq). Other assemblers that are based on string graphs (e.g., SGA), though less popular and also very slow, are indeed more favorable for longer reads.
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\nIn this thesis, I mainly present a new contig assembler called BASE, based on a seed-extension approach. It exploits an efficient indexing of reads to generate adaptive seeds with high probability of unique appearance in the genome and high sequencing quality. Guided by these seeds, BASE constructs extension trees and gradually removes the branches with a method called reverse validation, which utilizes information about read coverage and paired-end relationship to obtain consensus sequences of reads sharing the seeds. These consensus sequences are further extended to form high quality contigs.
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\nBenchmark on several bacteria and human datasets demonstrates the performance advantage of BASE in speed and assembly quality when longer reads are used. Our first benchmark was based on two datasets of deeply sequenced bacteria genomes (240X) with read length of 100bp and 250bp. Especially for 250bp reads, BASE performs much better than SOAPdenovo2 and SGA and is similar to SPAdes in performance. Regarding speed, BASE is consistently a few times faster than SPAdes and SGA, but still slower than SOAPdenovo2. We have further compared BASE and SOAPdenovo2 using human genome datasets with read length 100bp, 150bp and 250bp. BASE consistently achieves a higher N50 for all datasets; while the improvement becomes more significant when read length reaches 250bp. SOAPdenovo2 uses relatively more memory when sequencing error is high.
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\nBASE is an efficient assembler for contig construction, with significant improvement in quality for long NGS reads. It could be easily extended to support scaffolding in the near future.

Compliant force control in space docking is studied. Compliant force control strategy is developed based on the inner loop position control of 6-dof parallel robot in order to simulate push and pull process of forcible alignment in space docking. Compliant force control structure based on the inner position loop is introduced. The more systematic design methods of a serial PID type controller and a robust controller are presented in detail. Simulation and experiment results indicate efficiency of the designed force controllers and superiority of robust force controller.

Until recently, power semiconductors were usually produced as TO, power-PAK, and D-PAK style packaging, due to die size, thermal dissipation requirements, and the vertical flow of current through the devices. The introduction of GaN to power semiconductors has allowed manufactures to produce devices with approximately 9% the footprint of similar rated D-PAK Si MOSFETs. In addition, GaN semiconductors have much better theoretical limits of specific on-resistance to breakdown voltage, when compared to Si and SiC. As of now, GaN devices offer very good performance at much less the cost of SiC, very small footprints, no reverse recovery losses of a body diode, very low RDS(ON), and very fast turn-on and turn-off times due to QGS in single-digit nC range. GaN semiconductors are expected to make vast improvements over the next decade. Unfortunately, this decrease in package size has made design prototyping significantly more challenging. Traditional manual solder iron assembly is not sufficient for these devices. Difficulties include board design, device handling, alignment, solder reflow, flux residue removal, and post-assembly inspection. The EPC 2014 and 2015 devices both have a 4mm pitch and are 1.85mm2 and 6.70mm2, respectively. In many situations, the decreased pitch and small overall size of these devices mandate the use of automated assembly equipment, such as a pick & place, to ensure quality and repeatability of assembly. However, this may not be feasible for initial prototyping, due to cost and time constraints. Here we will present a technique for manual assembly of these chip scale devices, applied specifically to the EPC 2014 and 2015. This should decrease the cost and turn time for prototype assembly when utilizing these types of chip scale packaged power semiconductor devices.

For cost-beneficial reasons simulations with computer manikins have been increasingly used in the automotive industry for prediction of ergonomics problems before the product and work place exist in physical form. The main purpose of ergonomics simulations is to apply biomechanical models and data to assess the acceptability of the physical work load, e.g. working postures, visibility, clearance etc., which could result in requirements to change the design of the product. The aim is to improve ergonomics conditions in manual assembly and to promote a better product quality through improved assemblability (ease of assembly). Many studies have shown a clear correlation between assembly ergonomics and product quality and that poor assembly ergonomics result in impaired product quality and in decreased productivity. Nevertheless, there are remaining difficulties in achieving acceptance for changes of product and production solutions because of poor assembly ergonomics. A recent study in the Swedish automotive industry showed that huge savings and increased profit margins can be obtained by eliminating ergonomics risk concepts in the very early product development process. The study confirmed a strong relation between poor ergonomics assembly solutions and quality errors of the product (car). There was a substantially increased risk for quality errors and increased costs for corrective measures of the product for assembly items of high and moderate physical work load compared to assembly items of low work load. The quality risk was increased 3 and 3.7 times, respectively. The overall cost for corrective measures in the assembly plant and for factory complete cars was 8.7 and 8.2 times higher for assembly items of high and medium physical work load compared to items of low physical work load. The purpose of this paper is to demonstrate the need for ergonomics simulations of potentially harmful assembly concepts in combination with cost-benefit analyses of conceivable system solutions based on calculation of costs for quality errors related to poor ergonomics and poor assemblability. The intended end result of this research is a model by application of which it is possible to calculate the cost for quality losses and health effects due to poor ergonomics and compare it with the cost for improving the ergonomics with designers, manufacturing engineers and ergonomists as main users.

Hydrated aramid nanofiber network enhanced flexible expanded graphite films towards high EMI shielding and thermal properties

Modeling and evaluating of surface roughness prediction in micro-grinding on soda-lime glass considering tool characterization

Experimental Verification of Two New Theories Predicting Temperature-Dependent Viscosity Effects on the Forced Convection in a Porous Channel

Modelling and simulation of chatter in milling using a predictive force model