Browsing by Subject "Coils"
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Item Open Access All-surface induction heating with high efficiency and space invariance enabled by arraying squircle coils in square lattice(Institute of Electrical and Electronics Engineers, 2018) Kılıç, Veli Tayfun; Ünal, Emre; Yilmaz, N.; Demir, Hilmi VolkanThis paper reports an all-surface induction heating system that enables efficient heating at a constant speed all over the surface independent of the specific location on the surface. In the proposed induction system, squircle coils are placed tangentially in a two-dimensional square lattice as opposed to commonly used hexagonal packing. As a proof-of-concept demonstration, a simple model setup was constructed using a 3 × 3 coil array along with a steel plate to be inductively heated. To model surface heating, a set of six locations for the plate was designated considering symmetry points. For all of these cases, power dissipated by the system and the plate's transient heating were recorded. Independent from the specific plate position, almost equal heating speeds were measured for the similar levels of dissipated energies in the system. Using full three-dimensional electromagnetic solutions, the experimental results were also verified. The findings indicate that the proposed system is proved to enable energy efficient space-invariant heating in all-surface induction hobs.Item Open Access Innovative modular and arrayed coil systems for ultrahigh efficiency in inductive heating and automated metal detection(2016-12) Kılıç, Veli TayfunInduction systems have become increasingly more important and popular in our modern world and their application areas have widely expanded because of their high levels of safety and controllability. Today one important application of these induction systems is the inductive heating, which now finds use not only in conventional applications of point-source heating but also in new areas including all-surface heating with some degree of exibility in localization. The efficiency of such emerging systems, especially in planar structures across an entire surface, however, has thus far been limited compared to conventional inductive heating. In this thesis, to address these problems, we show a new class of strongly coupled planar coils that enhance magnetic coupling in square lattice stacking by design and with phase difference application in operation. These coils can be tiled in two-dimensional arrays in a modular fashion or to cover an arbitrarily large continuous surface. In a proof-of-concept realization, we experimentally demonstrated that these proposed outer squircle-inner circular coils outperform the conventional coils of circular shape. Using square-arrayed coil architecture, here we also present all-surface induction systems achieving uniform and enhanced heating speed for all loading positions no matter what the misalignment of the heated vessel with respect to the coils is. In addition, to solve the problems of automatically detecting metals over the whole surface together with determining their exact positions, we introduce a new method that relies on simultaneous wireless measurement and tracking of inductance-resistance of the coils at multiple frequencies to identify those coupled with the metal targets to be detected in the system. While pinpointing the location of the targeted metals, the proposed technique also identifies their material types. For future ubiquitous all-surface systems, this approach allows for automated sensing of metal vessels and powering the loaded coils for the highest possible performance independent of the specific location of each vessel with respect to coils. These findings indicate that the proposed innovative modular and arrayed coils enable, for the first time, full degree of exibility in localized inductive heating with space-invariance in all-surface heating.Item Open Access Projection onto epigraph sets for rapid self-tuning compressed sensing MRI(IEEE, 2019) Shahdloo, Mohammad; Ilıcak, Efe; Tofighi, Mohammad; Sarıtaş, Emine Ülkü; Çetin, A. Enis; Çukur, TolgaThe compressed sensing (CS) framework leverages the sparsity of MR images to reconstruct from undersampled acquisitions. CS reconstructions involve one or more regularization parameters that weigh sparsity in transform domains against fidelity to acquired data. While parameter selection is critical for reconstruction quality, the optimal parameters are subject and dataset specific. Thus, commonly practiced heuristic parameter selection generalizes poorly to independent datasets. Recent studies have proposed to tune parameters by estimating the risk of removing significant image coefficients. Line searches are performed across the parameter space to identify the parameter value that minimizes this risk. Although effective, these line searches yield prolonged reconstruction times. Here, we propose a new self-tuning CS method that uses computationally efficient projections onto epigraph sets of the ℓ1 and total-variation norms to simultaneously achieve parameter selection and regularization. In vivo demonstrations are provided for balanced steady-state free precession, time-of-flight, and T1-weighted imaging. The proposed method achieves an order of magnitude improvement in computational efficiency over line-search methods while maintaining near-optimal parameter selection.Item Open Access Strongly coupled outer squircle-inner circular coil architecture for enhanced induction over large areas(Institute of Electrical and Electronics Engineers Inc., 2016) Kilic V.T.; Unal, E.; Gonendik, E.; Yilmaz, N.; Demir, Hilmi VolkanThis paper reports a newly designed class of strongly coupled planar coil structures for the purpose of enhanced induction over large areas. These new architectures feature a squircle shape at the outer rim with rounded corners and straight sides evolved into a fully circular shape in the inner side, which proves to be essential to achieve high efficiency in arrays and all-surface inductive heating. As a proof-of-demonstration, a simple inductive heating system composed of a pair of side-by-side placed coils was constructed together with a ferrite layer. Experiments were repeated for 0° and 180° phase differences between coil currents. Here, the system efficiency was shown to be increased overall by 37.4% using outer squircle-inner circular coils instead of conventional circular coils. This comparative study indicates that the proposed coil architecture offers the potential for large-area, fast, and phase-insensitive inductive heating with high efficiency.Item Open Access Wireless metal detection and surface coverage sensing for all-surface induction heating(MDPI AG, 2016) Kılıç, Veli Tyfun; Ünal, Emre; Demir, Hilmi VolkanAll-surface induction heating systems, typically comprising small-area coils, face a major challenge in detecting the presence of a metallic vessel and identifying its partial surface coverage over the coils to determine which of the coils to power up. The difficulty arises due to the fact that the user can heat vessels made of a wide variety of metals (and their alloys). To address this problem, we propose and demonstrate a new wireless detection methodology that allows for detecting the presence of metallic vessels together with uniquely sensing their surface coverages while also identifying their effective material type in all-surface induction heating systems. The proposed method is based on telemetrically measuring simultaneously inductance and resistance of the induction coil coupled with the vessel in the heating system. Here, variations in the inductance and resistance values for an all-surface heating coil loaded by vessels (made of stainless steel and aluminum) at different positions were systematically investigated at different frequencies. Results show that, independent of the metal material type, unique identification of the surface coverage is possible at all freqeuncies. Additionally, using the magnitude and phase information extracted from the coupled coil impedance, unique identification of the vessel effective material is also achievable, this time independent of its surface coverage.