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In this paper, a misalignment-tolerant wireless charging system based on multidimensional cross-coupling for autonomous underwater vehicles (AUVs) is proposed. The four transmitting coils of the proposed system magnetic coupler are divided evenly into two pairs as bipolar transmitting units. Subsequently, the uniform multi-dimensional horizontal magnetic flux can be obtained by two current vectors with a 90° phase difference exciting in the bipolar transmitting units. For the receiver, a couple of orthogonal coils are designed to form cross-coupling with the transmitter to pick up the maximum magnetic flux. Then, the proposed magnetic coupler combined with the proposed transmitter and receiver is designed through finite element analysis. Finally, a 900 W prototype is built and tested. Experimental results show that the system has stable output characteristics in the ranges of a − 20° to 20° rolling misalignment and a − 30 to 30 mm axial misalignment. [ABSTRACT FROM AUTHOR]

Compact design in receiver and misalignment tolerance are two basic considerations for practical applications of wireless power transfer (WPT) in unmanned aerial vehicles (UAVs). To balance these two requirements, a novel magnetic design with the composite interval-acted parallel- & vertical-flux throw, orthogonal two-dimensional flux pick-up, and power-flow summed output is proposed in this letter. The resulting magnetic structure includes a target-shaped transmitter and two quadrature receivers, and the transmitter consists of four annular-type coils which are magnetized in a bipolar mode, making it possible to form a magnetic field with a parallel- and vertical-flux complementary distribution. Moreover, by integrating two orthogonal receiving coils into one receiver, a stable summed output current can supply the UAV onboard load with only a small size receiver. A UAV WPT prototype is established based on the proposal. The results show that the prototype can deliver 325 W with a system efficiency of 86%, and especially the variation of the output current is within ±0.76 A for different landing positions and directions. The overall system efficiency is from 87.3% down to 83.1%. [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicle (AUV) is a key mobile node in the ocean observation network. However, the limited endurance capacity and limited cruising range have become the bottlenecks in the wide application of the AUVs. In order to extend cruising range, this article develops a uniform power inductive power transfer (IPT) system for AUVs. A novel magnetic coupler with a low output fluctuation, low weight of receiver and a low space occupation of the AUV is proposed in this article. The proposed magnetic structure employing a quadruple-coil transmitter and a crossed dipole receiver utilizes uniform horizontal magnetic flux to establish stable coupling against rotational and axial misalignment. An IPT circuit topology is designed and analyzed in detail, meanwhile, the phase difference of the excitation currents is optimized to achieve the power and efficiency stability versus misalignments. The proposal is analyzed, established, and tested in this article. The magnetic receiver weighs only 414 g. The results show that the prototype can deliver 964.7 W with a dc–dc efficiency of 90.9%. In the process of rolling dislocation from –20° to 20° and axial dislocation from –30 mm to 30 mm, the maximum fluctuation of output power is 12.1% and 20.2%, respectively. [ABSTRACT FROM AUTHOR]

This letter develops a wireless charging system based on a novel orthogonal magnetic structure and primary-side power control to simplify the structure and reduce the weight of on-board pick-up for recharging the unmanned aerial vehicles (UAVs). The novel magnetic structure has a polarized transmitter with a flat U-type core and a perpendicular air-cored receiving coil, guaranteeing the magnetic flux operation space away from a UAV body by coil structure itself and also reducing the weight of a magnetic receiver. The power flow to the battery is controlled by the primary side based on charging current and voltage feedback by pick-up. Simulations based on ANSYS Maxwell and experiments are carried out to validate the proposal. The weight of a magnetic receiver is 130 g. And the system can deliver 500 W with a dc-to-battery efficiency of 90.8%, meanwhile 10 A constant current/50 V constant voltage charging for 12S lithium-ion battery is achieved by the closed-loop system. [ABSTRACT FROM AUTHOR]

This paper proposes a novel inductive and capacitive combined wireless power transfer (IC-WPT) system for unmanned aerial vehicle (UAV) applications. First, a new compact inductive and capacitive combined coupler is presented. The magnetic field coupled power transmission of the compact coupler contains one magnetic transmitting unit, which is composed of two biorthogonal L-type cores and two rectangular coils wound on each of the short edges of the L-type ferrite core in the vertical position, and two air-cored receiving coils embedded in the legs. Meanwhile, the electric field coupled power transmission of the compact coupler consists of four pieces of copper foil, where two are attached on the primary side and two are attached on the secondary sides for wireless energy transmission through capacitive coupling. Second, a simple resonant compensation network is developed for the IC-WPT system. To make the secondary side lightweight, the receiver self-inductance of the inductive power transfer (IPT) coupler and compensating capacitance of the capacitive power transfer (CPT) receiver can be used to compensate each other. A prototype of the proposed UAV IC-WPT system is built and tested. Experimental results show that the wireless power transfer system can deliver 130 W at an efficiency of 81.2%, which means it can be adopted to the autonomous charging of UAVs. [ABSTRACT FROM AUTHOR]

In the research of drone wireless charging, the lightweight design of the wireless charging device has a large impact on the overall performance of the drone. To realize the lightweight, the tubular coil, which caused by high‐frequency excitation to produce skin effect in the conductor becomes a way to optimize the weight of the receiver coil. This paper proposes an aluminum tube with a thin copper layer plated on the surface as a drone receiver coil and landing gear. This solution can not only replace the original bracket but also be lightweight and obtain high coupling coefficient. Experiments show that this novel receiver can receive power up to 30 W at 250 kHz excitation source with 78% average transmission efficiency and has good antimisalignment ability. This new tubular coupler is more suitable for the demand of lightweight wireless charging for drones. [ABSTRACT FROM AUTHOR]

A magnetic arc oscillation system for tungsten inert gas (TIG) narrow gap welding is developed to prevent insufficient sidewall fusion and improve efficiency and quality for thick component welding. The characteristic of the system is that a double magnetic pole is induced by exciting current flowing through the field coil to generate the magnetic field within the welding area. This optimization of double magnetic pole not only enhances magnetic flux density compared with conventional single magnetic pole but also provides reliable melting of the sidewall. In this article, a new experimental method for the determination of the resulting heat input into the workpiece is proposed. Measurements of arc voltage and welding current flowing through the sidewalls are used to validate the redistribution of the arc heat. Furthermore, the difference of linear heat input of the sidewalls caused by current division ratio difference and arc voltage difference was the main reason why the formation characteristics occurred. [ABSTRACT FROM AUTHOR]

Due to the galvanic isolation and excellent bidirectional power-transfer capacity, the symmetrical CLLC-resonant dc transformer (DCT) has received increasing attention and has been popularly adopted in dc microgrid. However, for good comprehensive performance, there are some concerns in the design of CLLC-resonant DCT. First, when it operates individually, its voltage transfer ratio (VTR) is hard to maintain within an acceptable range when fluctuations of inductance or capacitance exist in practice. Second, when the CLLC-resonant DCT operates in a cascaded system with a constant power load, impedance interactions may result in instability phenomenon. The fluctuations of inductance or capacitance will also affect the stability of this cascaded system. In order to deal with these concerns, a parameter design approach for the CLLC-resonant DCT is put forward in this article. A particle swarm optimization algorithm is specially applied to realize thorough considerations of unpredictable parameter fluctuations. Thus, the designed CLLC-resonant DCT is able to maintain robust VTR and system stability when circuit parameter fluctuations exist. In the end, a 1-kW prototype has proved the validity of this proposed design approach. [ABSTRACT FROM AUTHOR]

In this article, existed Lyapunov-based control methods for stand-alone inverters either have a single control loop accompanied with steady-state errors or dual control loops at the sacrifice of negative definiteness of the derivative of the Lyapunov function. Besides, load-current sensors or observers are indispensable in these methods. Proposed Lyapunov-based control inherently has dual control loops that can rigorously guarantee the global large-signal stability of the system. Meanwhile, load disturbance is suppressed adaptively without any load-current sensors or observers. Stability analysis proves that the proposed method is valid both for a linear and nonlinear load. The proposed approach complies with the internal model principle, leading to the minimized steady-state error. An adaptive weighted Lyapunov function (V) is proposed to derive the dual-loop control law and adaptive law. The closed-loop system is inherently d–q decoupled. Three controller gains are tuned quantitatively via explicit formulas based on pole-placement strategy. Simulation and experimental results demonstrate that the proposed method has good steady-state and dynamic performance with great robustness against the parametric mismatch. [ABSTRACT FROM AUTHOR]

In this paper, a novel large current rectifier using the fork-connected autotransformer and dc-side current injection method is proposed. The fork-connected autotransformer outputs two sets of three-phase voltages with 60° phase difference, and feeds two three-phase half-wave rectifiers. Compared with the isolated line-frequency transformer, the proposed autotransformer has lower kilovoltampere (kVA) rating under the same load power. An optimal designed single-phase full-bridge inverter is used to inject the compensation currents into the dc side of the two three-phase half-wave rectifier, which can reduce the harmonics in input line current to be an acceptable level. The kVA rating of the single-phase full-bridge inverter is very lower, and the proposed large current rectifier draws nearly sinusoidal currents from the ac main after using the dc-side injection. A 4 kW prototype is set up to validate the theoretical analysis and evaluate the performance. [ABSTRACT FROM PUBLISHER]

[Display omitted] • The heating allocation with wire wobbling is reconstructed by simulation analysis. • Complete sidewall penetration and concave weld shape are achieved. • The heat transfer and dissipation in multi-pass welding process are explained. • The relationship between thermal cycle, microstructure and performance is revealed. A novel, new approach of narrow gap laser wire feeding welding (NG-LWFW) with electromagnetic assisted wire wobbling is proposed to solve incomplete sidewall fusion and improve solidification morphology. The energy distribution and fusion zone formation during multi-pass NG-LWFW process are clarified. The melt pool is driven into sidewall position and the melted metal accumulates towards that side groove, leading to the increase of sidewall penetration with concave bead profile. The simulation results show that the wire wobbling obviously reduces peak temperature of melt pool and increases sidewall temperature. The heat affected zone (HAZ) width reduced, and a finer and diversity weld microstructure is presented. As multi-pass welding proceeds, the former weld is heat-treated by the latter weld, leading to the re-melting of columnar grains and increasing diversity of interlayer grains. The columnar crystal zone is refining and a narrower dendrite spacing of δ-ferrite phase is found with deposited filling layers. The micro-hardness of weld centerline shows an overall increase trend and the impact energy increases with denser dimples from the bottom layer to upper layer. [ABSTRACT FROM AUTHOR]

• Electromagnetic assisted wire wobbling is proposed to regulate melt flow. • Electromagnetic swing wire can enlarge melt pool and improve sidewall wetting. • Lack of fusion defect is solved and concave surface morphology is obtained. • Uniform temperature, element distribution and grain refinement are achieved. A novel, new approach of electromagnetic assisted wire wobbling to regulate energy allocation, melt flow and metallurgical structure is introduced in laser narrow gap welding of 316 L stainless steel. The formation of melt pool, weld surface morphologies and microstructure features in conventional laser welding, laser wobble welding and electromagnetic assisted wire wobble welding were compared. The results reveal that the forced convection generated by electromagnetic swing wire could broaden the melt pool size and compulsively push high-temperature weld metal towards groove sidewall. The wetting of liquid weld metal on groove sidewall was improved and concave weld morphology was obtained, thereby avoiding incomplete fusion of sidewall and favoring the filling of next weld bead. The temperature and element distribution in weld zone would be more uniform by the periodically and drastically forced convection, which helped to inhibit the growth of columnar crystals and promote the uniform distribution of elements. The average microhardness value in weld zone was uniform with the using of electromagnetic swing wire. Moreover, mechanisms of enhanced sidewall wetting and grain refinement were discussed in electromagnetic assisted wire wobble laser welding. [ABSTRACT FROM AUTHOR]