Search Results (45)

Wireless power transfer (WPT) systems for autonomous underwater vehicles (AUVs) are gaining traction in marine exploration due to their operational convenience, safety, and flexibility. Nevertheless, disturbances from ocean currents and marine organisms frequently induce rotational, axial, and air-gap misalignments, significantly degrading the output power stability. To mitigate this issue, this paper proposes a novel reconfigurable WPT system utilizing coaxial antipodal dual DD (CAD-DD) coils, which strategically switches between a detuned S-LCC topology and a detuned S-S topology at a fixed operating frequency. By characterizing the output power versus the coupling coefficient (P-k) profiles under both reconfiguration modes, a parameter design methodology is developed to ensure stable power delivery across wide coupling variations. Experimental validation using a 1.2 kW AUV charging prototype demonstrates remarkable tolerance to misalignment: ±30° rotation, ±120 mm axial displacement, and 20–50 mm air-gap variation. Within this range, the output power fluctuation is confined to within 5%, while the system efficiency exceeds 85% consistently, peaking at 91.56%. Full article

Wireless power transfer systems require not only strong coupling capabilities but also stable output under various misalignment conditions. This paper proposes a hybrid magnetic coupler for autonomous underwater vehicles (AUVs), featuring two identical arc-shaped rectangular transmitting coils and a combination of an arc-shaped rectangular receiving coil and two anti-series connected solenoid coils. The arc-shaped rectangular receiving coil captures the magnetic flux generated by the transmitting coil, which is directed toward the center, while the solenoid coils capture the axial magnetic flux generated by the transmitting coil. The parameters of the proposed magnetic coupler have been optimized to enhance the coupling coefficient and improve the system’s tolerance to misalignments. To verify the feasibility of the proposed magnetic coupler, a 300 W prototype with LCC-S compensation topology is built. Within a 360° rotational misalignment range, the system’s output power maintains around 300 W, with a stable power transmission efficiency of over 92.14%. When axial misalignment of 40 mm occurs, the minimum output power is 282.8 W, and the minimum power transmission efficiency is 91.6%. Full article

This paper proposes a method for array design and optimal transmitting coil selection of underwater wireless power transfer systems. This method is divided into three steps. Firstly, by analyzing the influence of different ratio side lengths of the transmitting coil and receiving coil on mutual inductance, the optimal ratio side length coil is selected. Secondly, by analyzing the relative size of the reflection impedance of the power supply coil and its surrounding coils, the optimal coil activation criterion is derived. Finally, by estimating the position of the receiving coil without communication, the switching of the power supply coil is realized. According to the proposed method, it was verified on the experimental platform. Under a rated power of 300 W with a load resistance of 20 Ω, the system maintains efficiency ≥ 80% even under horizontal offsets up to 150 mm (75% of the transmitting coil side length) and two-dimensional offsets up to 200 mm (100% of the transmitting coil side length). Full article

This paper proposes a 1000 W high-frequency three-phase power inversion underwater capacitive wireless power transfer (UCWPT) system for power delivery to autonomous underwater vehicles (AUVs). The multi-phase coupling structure is designed as a columnar configuration that conforms to the shape of AUVs. This paper innovatively presents a curved coupling coupler composed of six metal plates. This design significantly enhances the mutual capacitance of the coupling structure and the power transfer capacity of the UCWPT system. Utilizing the columnar structure, the receiver of the capacitive wireless power transfer system can be easily integrated into AUVs, reducing the installation space. Furthermore, the cylindrical dock-transmitter terminal structure of the system greatly improves the anti-misalignment capability. This addresses issues such as charging voltage and current fluctuations caused by vehicle rolling in dynamic ocean environments. Additionally, the wireless power transfer capacity is notably enhanced. An experimental platform was constructed, and tests were conducted in both air and water media. A 1000 W experimental setup was developed to validate the theoretical analysis and simulations. The experimental results align closely with the theoretical predictions. At a fixed distance of 3 cm between transmitter and receiver, peak power transfer efficiencies of 80% in air and 74% in water were achieved with stable operational performance. The cylindrical structure demonstrates robust anti-misalignment properties. Full article

This work presents a high-speed hybrid communication system integrating Underwater Optical Wireless Communication (UOWC), Multimode Fiber (MMF), and Free-Space Optics (FSO) channels, leveraging Orbital Angular Momentum (OAM) beams for enhanced data transmission. A Photodetector, Remodulate, and Forward Relay (PRFR) is employed to enable wavelength conversion from 532 nm for UOWC to 1550 nm for MMF and FSO links. Four distinct OAM beams, each supporting a 5 Gbps data rate, are utilized to evaluate the system’s performance under two scenarios. The first scenario investigates the effects of absorption and scattering in five water types on underwater transmission range, while maintaining fixed MMF length and FSO link. The second scenario examines varying FSO propagation distances under different fog conditions, with a consistent underwater link length. Results demonstrate that water and atmospheric attenuation significantly impact transmission range and received optical power. The proposed hybrid system ensures reliable data transmission with a maximum overall transmission distance of 1125 m (comprising a 25 m UOWC link in Pure Sea (PS) water, a 100 m MMF span, and a 1000 m FSO range in clear weather) in the first scenario. In the second scenario, under Light Fog (LF) conditions, the system achieves a longer reach of up to 2020 m (20 m UOWC link + 100 m MMF span + 1900 m FSO range), maintaining a BER ≤ 10⁻⁴ and a Q-factor around 4. This hybrid design is well suited for applications such as oceanographic research, offshore monitoring, and the Internet of Underwater Things (IoUT), enabling efficient data transfer between underwater nodes and surface stations. Full article

A constant current constant voltage charging scheme based on a single-ended primary inductive converter is proposed to address the key issues of wireless power transfer (WPT) technology for charging devices in seawater environments. The scheme can effectively adapt to the complex transmission conditions of a WPT system in a seawater environment by using the advantages of single-ended primary inductor converter (SEPIC) topology, such as adjustable voltage, wide input range, and the same polarity as output; its regulating effect on charging current and voltage is modeled and analyzed. An underwater experimental platform is built to test the charging performance of the system under different transmission distances, radial offsets, and deflection angles (1 A is set for the constant current stage and 5 V for the constant voltage stage). The experimental results show that when the distance is 2 cm, the maximum fluctuation amplitude of the current is 0.04 A. When the transmission distance is increased to 6 cm, and a radial offset of 5 cm is introduced, the fluctuation amplitude increases to 0.13 A. Under the condition of dynamic charging, the maximum fluctuation range of current is 0.15 A, and the fluctuation rate reaches 16.7%. It shows that the system has good applicability and application prospects in seawater environments. Full article

With the growing use of unmanned surface vehicles (USVs) for underwater exploration, efficient wireless charging solutions like inductive power transfer (IPT) are crucial for addressing power limitations. This paper presents a novel IPT system for USVs and introduces a systematic design approach for optimizing magnetic couplers. The proposed design addresses three critical challenges: misalignment tolerance, lightweight construction, and thermal safety, which are intricately linked through a magnetic field. In terms of misalignment, this paper demonstrates that the coil length is a key factor in determining misalignment tolerance. For a lightweight design, replacing the ferrite plate with ferrite bars can significantly reduce the weight of the coupler without causing core saturation. The design is further validated through a two-way coupled electromagnetic–thermal simulation. The results reveal that, with proper thermal management, the system avoids thermal risks in underwater environments compared to air. Finally, a 3 kW prototype is constructed and tested in fresh water, achieving 55 V and 50 A wireless charging at an 85.7% full-load dc-to-dc efficiency, thus confirming the practicality and performance of the design. Full article

Wireless power transfer (WPT) technology applied to underwater environments has the advantages of no electrical contact, high safety, and high applicability. Underwater capacitive power transfer (UCPT) technology shows great potential in the field of underwater wireless power transfer as it has more advantages compared to underwater inductive power transfer (UIPT) technology. This paper begins with the system principles of UCPT and explains the advantages of UCPT technology for underwater applications. It then reviews the coupler and equivalent circuit models currently used for UCPT in various underwater environments, which indicates the direction for the design of underwater couplers in the future. In addition, compensation networks currently applied in UCPT systems are summarized and compared. Furthermore, different application examples of UCPT are introduced, and the key factors constraining UCPT development are pointed out. Research directions for future development of UCPT technology are also investigated. Full article

Building a reliable and optimum underwater optical wireless communication (UOWC) system requires identifying all potential factors that cause the attenuation and dispersion of the optical signal. The radiative transfer equation (RTE) solution can be utilised to conclude these essential design parameters to build an optimum UOWC system. RTE has various numerical and simplified analytical solutions with varying reliability and capability scope. Many scientists consider the Monte Carlo simulation (MCS) method to be a consistent and widely accepted approach to formulating an RTE solution, which models the propagation of photons through various underwater channel environments. MCS recently attracted attention because we can build a reliable model for underwater environments. Based on such a model, this report demonstrates the resulting received optical power distribution as an output for an array of emulation inputs, including transmitted light’s spatial and temporal distribution, channel link regimes, and associated impairments. This study includes a survey component, which presents the required framework’s foundation to establish a valid RTE model, which leads to solutions with different scopes and depths that can be drawn for practical UOWC use cases. Hence, this work shows how underlying modelling elements can influence a solution technique, including inherent optical properties (IOPs), apparent optical properties (AOPs), and the potential limitations of various photon scattering function formats. The work introduces a novel derivation of mathematical equations for single- and multiple-light-pulse propagation in homogeneous and inhomogeneous channels, forming the basis for MCS-based UOWC studies. The reliability of MCS implementation is assessed using compliance with the Central Limit Theorem (CLT) and leveraging the Henyey–Greenstein phase function with full-scale random selection. As part of the tutorial component in this work, the MCS inner working is manifested using an object-oriented design method. Therefore, this work targets researchers interested in using MCS for UOWC research in general and UOWC photon propagation in seawater channel modelling in general. Full article

This study presents a comprehensive model for ultrasonic energy transfer (UET) using a 33-mode piezoelectric transducer to advance wireless sensor powering in challenging environments. One of the advantages of UET is that it is not stoppable by electromagnetic shielding and can penetrate metal. Existing models focus on feasibility and numerical analysis but lack an effective link between input and output power in different media applications. The proposed model fills this gap by incorporating key factors of link loss, including resonant frequency, impedance matching, acoustic coupling, and boundary conditions, to predict energy transfer efficiency more accurately. The model is validated through numerical simulations and experimental tests in air, metal, and underwater environments. An error analysis has shown that the maximum error between theoretical and experimental responses is 3.11% (air), 27.37% (water), and 1.76% (aluminum). This research provides valuable insights into UET dynamics and offers practical guidelines for developing efficient wireless powering solutions for sensors in difficult-to-access or electromagnetically shielded conditions. Full article

In this work, we consider a point-to-point underwater optical wireless communication scenario where an underwater sensor (US) transmits its sensing data to a remotely operated vehicle (ROV). Before the US transmits its data to the ROV, the ROV performs simultaneous lightwave information and power transfer (SLIPT), delivering both control data and lightwave power to the US. Under the considered scenario, our objective is to maximize energy harvesting at the US while supporting predetermined communication performance between the two nodes. To achieve this objective, we develop a hierarchical deep Q-network (DQN)–deep deterministic policy gradient (DDPG)-based online algorithm. This algorithm involves two reinforcement learning agents: the ROV and US. The role of the ROV agent is to determine an optimal beam-divergence angle that maximizes the received optical signal power at the US while ensuring a seamless optical link. Meanwhile, the US agent, which is influenced by the decision of the ROV agent, is responsible for determining the time-switching and power-splitting ratios to maximize energy harvesting without compromising the required communication performance. Unlike existing studies that do not account for adaptive parameter control in underwater SLIPT, the proposed algorithm’s adaptive nature allows for the dynamic fine-tuning of optimization parameters in response to varying underwater environmental conditions and diverse user requirements. Full article

Efficiency has always been one of the most critical indicators for evaluating wireless power transfer (WPT) systems. To achieve fast maximum energy efficiency tracking (MEET), this paper provides an innovative control method utilizing the hill climbing-golden section search (HC-GSS) method of an LCC-S compensated WPT system. The receiver side includes a buck-boost converter that regulates the output current or voltage to meet output requirements. In the meantime, the buck-boost converter on the transmitter side is managed by the HC-GSS approach for MEET by minimizing the input power under the premise of output stability. Compared with the conventional P&O method, the HC-GSS method can eliminate the trade-off between the oscillation and convergence rate because it is designed for different system stages. In this WPT system, there is no need for direct communication between the transmitter and receiver. Therefore, the system is potentially cheaper to implement and does not suffer from annoying communication delays, which are prevalent in underwater environments for unmanned underwater vehicles’ (UUV) WPT systems. Both the simulation and experiment results show that this method can improve the efficiency of the WPT system without communication. The proposed method remains valid with coupler displacement as it does not include the mutual inductance of the system. Full article

Compared to the traditional wet-mate underwater power supply method, Magnetic Coupling Resonant Wireless Power Transfer (MCR-WPT) technology boasts advantages such as excellent insulation, high safety, and convenient operation, showing promising application prospects in the field of power supply for underwater vehicles and other mobile underwater devices. In order to explore the transmission characteristics of this technology underwater, this article first establishes a traditional mathematical model, and then modifies the underwater model through analysis of changes in coil self-inductance and mutual inductance, as well as the impact of eddy current losses. Using the modified mathematical model of the underwater MCR-WPT system, the transmission characteristics are analyzed, and simulations and experimental validations are performed using MATLAB R2022a software. In the study of frequency characteristics, it is found that the system operates optimally when both ends of the circuit work at the resonant state; that is, when f_input = f_resonance = 100 kHz, the output performance is at its best, and the optimal resonant frequency significantly improves power and transmission efficiency. When the input frequency is less than 87.3 kHz or greater than 122.9 kHz, the output power decreases to less than half of the maximum power. In the investigation of load effects, the optimal load for maximizing system output power was identified, but the load that maximizes transmission efficiency is different from this optimal load. This study provides strong theoretical support and guidance for improving the performance of underwater wireless power transmission systems. Full article

Magnetically coupled resonant wireless power transfer (MCR-WPT) technology offers longer effective transmission distances and higher efficiency compared to traditional charging methods, making it better suited to the prolonged and efficient operation of autonomous underwater vehicles. This paper first establishes a traditional mathematical model and then refines it while analyzing the variations in the self-inductance and mutual inductance of underwater coils. To further enhance the system’s performance, a multi-objective optimization of the coupling mechanism is conducted. An orthogonal experiment is employed to determine the effects of various influencing factors on the coils’ self-inductance and mutual inductance. Subsequently, an RBF neural network is used to create a regression prediction model based on the results of the orthogonal experiment. The NSGA-II algorithm is then applied for the multi-objective optimization of the coupling mechanism, resulting in a Pareto front solution set. The optimized efficiency is 93.35%, representing an approximately 6% improvement over the original system, with the power density increasing from ${1.267\times 10}^6 \mathrm{W}/{\mathrm{m}}^3$ before optimization to ${4.782\times 10}^6 \mathrm{W}/{\mathrm{m}}^3$ after optimization. Significant enhancement in system performance is achieved. Full article

In recent years, underwater wireless ultrasonic energy transmission technology (UWUET) has attracted much attention because it utilizes the propagation characteristics of ultrasound in water. Effectively evaluating the performance of underwater ultrasonic wireless energy transmission is a key issue in engineering design. The current approach to performance evaluation is usually based on the system energy transfer efficiency as the main criterion, but this criterion mainly considers the overall energy conversion efficiency between the transmitting end and the receiving end, without an in-depth analysis of the characteristics of the distribution of the underwater acoustic field and the energy loss that occurs during the propagation of acoustic waves. In addition, existing methods focusing on acoustic field analysis tend to concentrate on a single parameter, ignoring the dynamic distribution of acoustic energy in complex aquatic environments, as well as the effects of changes in the underwater environment on acoustic propagation, such as spatial variability in temperature and salinity. These limitations reduce the usefulness and accuracy of models in complex marine environments, which in turn reduces the efficiency of acoustic energy management and optimization. To solve these problems, this study proposes a method to evaluate the performance of underwater ultrasonic energy radiation based on the spatial distribution characteristics of acoustic power. By establishing an acoustic power distribution model in a complex impedance–density aqueous medium and combining numerical simulation and experimental validation, this paper explores the spatial variation of acoustic power and its impact on the energy transfer efficiency in depth. Using high-resolution spatial distribution data and actual environmental parameters, the method significantly improves the accuracy of the assessment and the adaptability of the model in complex underwater environments. The results show that, compared with the traditional method, this method performs better in terms of the accuracy of the acoustic energy radiation calculation results, and is able to reflect the energy distribution and spatial heterogeneity of the acoustic source more comprehensively, which provides an important theoretical basis and practical guidance for the optimal design and performance enhancement of the underwater ultrasonic wireless energy transmission system. Full article