2,476 research outputs found

    NOVEL METHODS FOR PERMANENT MAGNET DEMAGNETIZATION DETECTION IN PERMANENT MAGNET SYNCHRONOUS MACHINES

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    Monitoring and detecting PM flux linkage is important to maintain a stable permanent magnet synchronous motor (PMSM) operation. The key problems that need to be solved at this stage are to: 1) establish a demagnetization magnetic flux model that takes into account the influence of various nonlinear and complex factors to reveal the demagnetization mechanism; 2) explore the relationship between different factors and demagnetizing magnetic field, to detect the demagnetization in the early stage; and 3) propose post-demagnetization measures. This thesis investigates permanent magnet (PM) demagnetization detection for PMSM machines to achieve high-performance and reliable machine drive for practical industrial and consumer applications. In this thesis, theoretical analysis, numerical calculation as well as experimental investigations are carried out to systematically study the demagnetization detection mechanism and post-demagnetization measures for permanent magnet synchronous motors. At first a flux based acoustic noise model is proposed to analyze online PM demagnetization detection by using a back propagation neural network (BPNN) with acoustic noise data. In this method, the PM demagnetization is detected by means of comparing the measured acoustic signal of PMSM with an acoustic signal library of seven acoustical indicators. Then torque ripple is chosen for online PM demagnetization diagnosis by using continuous wavelet transforms (CWT) and Grey System Theory (GST). This model is able to reveal the relationship between torque variation and PM electromagnetic interferences. After demagnetization being detected, a current regulation strategy is proposed to minimize the torque ripples induced by PM demagnetization. Next, in order to compare the demagnetization detection accuracy, different data mining techniques, Vold-Kalman filtering order tracking (VKF-OT) and dynamic Bayesian network (DBN) based detection approach is applied to real-time PM flux monitoring through torque ripple again. VKF-OT is introduced to track the order of torque ripple of PMSM running in transient state. Lastly, the combination of acoustic noise and torque is investigated for demagnetization detection by using multi-sensor information fusion to improve the system redundancy and accuracy. Bayesian network based multi-sensor information fusion is then proposed to detect the demagnetization ratio from the extracted features. During the analysis of demagnetization detection methods, the proposed PM detection approaches both form torque ripple and acoustic noise are extensively evaluated on a laboratory PM machine drive system under different speeds, load conditions, and temperatures

    Validation of Radiocarpal Joint Contact Models Based On Images from a Clinical MRI Scanner

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    Due to the severity and continuing escalation in occurrences of degenerative joint diseases, it is vital to establish a means of detection and prevention that could lead to an improvement in quality of life. One such means is MRI-based modeling for joint contact analysis of in vivo functional loading. The purpose of this study was to validate models generated from a clinical MR scanner for future in vivo joint contact analyses. Models were tested using 3 cadaver forearm specimens and compared with experimental data. It was found that models were validated based on contact area. Direct contact area measurements were observed to be very close to experimental data. Model force measurements were reasonable, but did not agree with experimental data as well as contact area. Peak pressure data from the models were less consistent in correspondence with experimental data. Also, radiocarpal mechanics were investigated to determine the effect of inserting a sensor into the joint space. Magnitudes of bone motions were found to be greater with film inserted than without film. Model results showed contact areas to be higher with film than without film

    Eco‐Holonic 4.0 Circular Business Model to  Conceptualize Sustainable Value Chain Towards  Digital Transition 

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    The purpose of this paper is to conceptualize a circular business model based on an Eco-Holonic Architecture, through the integration of circular economy and holonic principles. A conceptual model is developed to manage the complexity of integrating circular economy principles, digital transformation, and tools and frameworks for sustainability into business models. The proposed architecture is multilevel and multiscale in order to achieve the instantiation of the sustainable value chain in any territory. The architecture promotes the incorporation of circular economy and holonic principles into new circular business models. This integrated perspective of business model can support the design and upgrade of the manufacturing companies in their respective industrial sectors. The conceptual model proposed is based on activity theory that considers the interactions between technical and social systems and allows the mitigation of the metabolic rift that exists between natural and social metabolism. This study contributes to the existing literature on circular economy, circular business models and activity theory by considering holonic paradigm concerns, which have not been explored yet. This research also offers a unique holonic architecture of circular business model by considering different levels, relationships, dynamism and contextualization (territory) aspects

    Stress Shielding Minimized In Femoral Hip Implants A Finite Element Model Optimized By Virtual Compatibility

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    Bone mechanics and traditional implant materials produce a recurring problem for patients of total hip arthroplasty (THA): the bone is “shielded” from the loading it has become accustomed to over many years of development. Bone adheres to what is called “Wolff’s Law”, meaning it is an adaptive structure which adjusts its geometry based on the loads experienced over its life (Pearson; Goldstein). As the new femoral hip implant transmits reduced stresses to the remaining bone, bone tissue atrophies at the interface, permitting loosening of the implant, pain, and thereby obliging additional surgery to correct the issue (Meade). In the present work, a methodology is endeavored for creating an innovative design for femoral hip implants. The approach uncouples the finite element implant model from the bone model, in order to focus solely on expected behavior within the implant while considering the varying material behavior in unique directions and locations. The implant’s internal geometry is optimized in order to better match typical, intact bone conditions. The eventual design reduces extreme changes in stresses within remnant bone such that the implant will remain implanted for greater periods of time without additional surgical attention

    A total hip replacement toolbox : from CT-scan to patient-specific FE analysis

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    Preliminary and advanced structural design of a three-modal camber morphing wing flap for large civil aircraft applications

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    Researchers and engineers design modern aircraft wings to reach high levels of efficiency with the main outcome of weight saving and airplane lift-to-drag ratio increasing. Future commercial aircraft need to be mission-adaptive to improve their operational efficiency. Within the framework of Clean Sky 2 Airgreen 2 (REG-IADP) European research project, a novel multifunctional morphing flap technology was investigated to improve the aerodynamic performances of the next Turboprop regional aircraft (90 passengers) along its flight mission. The proposed true-scale device (5 meters span with a mean chord of 0.6 meters) is conceived to replace and enhance conventional Fowler flap with new functionalities. Three different functions were enabled: overall airfoil camber morphing up to +28 deg (mode 1), +/- 10 deg (upwards/downwards) deflections of the flap tip segment (mode 2), flap tip twist of +/- 5 deg along the outer flap span (mode 3). Morphing mode 1 is supposed to be activated during take-off and landing only to enhance aircraft high-lift performances and steeper initial climb and descent. Thanks to this function, more airfoil shapes are available at each flap setting and therefore a dramatic simplification of the flap deployment system may be implemented. Morphing modes 2 and 3 are enabled in cruise and off-design flight conditions to improve wing aerodynamic efficiency. The proposed structural concept consists of a multi-box arrangement activated by segmented ribs with embedded inner mechanisms to realize the transition from the baseline configuration to different target aero-shapes while withstanding the aerodynamic loads. Lightweight and compact actuating leverages driven by electromechanical motors were properly integrated to comply with demanding requirements for real aircraft implementation: minimum actuating torque, minimum number of motors, reduced weight, and available design space. The methodology for the design of the inner mechanisms is based on a building block approach where the instant centres analysis tool is used to preliminary select the locations of the hinges’ leverages. The structural layout of an Adaptive Twist composite Tab was considered as a promising concept to balance the conflicting requirements between load-carrying capability and shape adaptivity in morphing lightweight structures. Finally, the embedded system functionality of the actuation system coupled with the structural skeleton is fully investigated by means of detailed finite element simulations. Results of actuation system performances, and aeroelastic deformations considering limit aerodynamic loads demonstrate the potential of the proposed structural concepts to be energy efficient, and lightweight for real aircraft implementation

    Symmetry in Structural Health Monitoring

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    In this Special Issue on symmetry, we mainly discuss the application of symmetry in various structural health monitoring. For example, considering the health monitoring of a known structure, by obtaining the static or dynamic response of the structure, using different signal processing methods, including some advanced filtering methods, to remove the influence of environmental noise, and extract structural feature parameters to determine the safety of the structure. These damage diagnosis methods can also be effectively applied to various types of infrastructure and mechanical equipment. For this reason, the vibration control of various structures and the knowledge of random structure dynamics should be considered, which will promote the rapid development of the structural health monitoring. Among them, signal extraction and evaluation methods are also worthy of study. The improvement of signal acquisition instruments and acquisition methods improves the accuracy of data. A good evaluation method will help to correctly understand the performance with different types of infrastructure and mechanical equipment

    Stresses Associated with Subchondral Bone Cysts - A Finite Element Analysis on an Extended Stifle Joint

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    Subchondral cystic lesions (SCL), sometimes referred to as subchondral bone cysts (SBC) or subchondral lucencies, occur in the medial femoral condyle (MFC) of horses and can cause lameness. They are more common in horses ≤ 2 years of age, but can occur in older horses. The causes of SCL are not well understood, however, trauma and osteochondrosis are most commonly implicated. Radiographs of young horses that develop SCLs indicate a progression from sclerosis to MFC flattening, and then a defect (SCL) that enlarges. Treatments are directed at reducing local inflammation and promoting bone and cartilage healing, with approximately 50-75% of horses becoming sound enough for work. However, bone healing after surgery is inconsistent, occurring in <20% of patients. Recently, a treatment of MFC SCL using a lag screw was reported to improve the rate of lameness resolution and is the first study to report significant and consistent bone healing. This suggests a biomechanical approach can improve the treatment of equine SCL, but very little is known about the stresses within the equine stifle and how the surgical procedure may be optimized. The equine stifle is a complex biological system and direct collection of biomechanical data would be difficult, if not impossible. The objective of this current study is to investigate the stresses in the subchondral femoral bone at different stages of cyst progression using finite element analysis. This information can help us better understand the mechanics associated with SCLs that will allow clinicians to develop and implement rational treatment strategies
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