Power Transfer Unit Research Articles

Problems of testing and operation of hydraulic power transfer units

The purpose and principles of operation of a civil aircraft emergency system including a power transfer unit are considered. Problems and trends of the development of piston hydraulic machines in aircraft construction are analyzed. The parameters of power transfer units used on 12 types of passenger airplanes are analyzed. The scenarios of failure of power transmission units are considered. The main directions of solving the problems of operation, as well as the requirements to design and testing are outlined.

Design of continuous repeater power transmission coil for wireless power transfer system for EVs with consideration of vehicle deviation

In recent years, EVs have become increasingly popular around the world, and research on wireless power supply technology for EV driving has progressed accordingly. In order to realize this wireless power transfer system for EVs on a real scale, it is necessary to lengthen the power transfer section per power transfer unit and to secure a sufficient power transfer section with a small number of power transfer units as a whole. To solve this problem, the single coil method, in which one coil is lengthened, has been proposed. However, as the coil length increases, resistance loss increases and efficiency decreases. Therefore, a repeater coil system has been proposed. In this in-transit power-feeding system, it is necessary to consider transient phenomena when the EV to be fed deviates from the feeding lane. Therefore, we propose a new repeater coil configuration on the transmission side that assumes a no-load condition. In this study, a new repeater coil system combining rectangular coils and orthogonal coils is proposed, which enables stable feeding of power to EVs by rectangular coils and response to transient phenomena. A comparison was also made with the single coil method that has been studied previously.

A New Multilevel Inverter Based Grid Connected Reliable Solar Power Transfer Unit With Power Quality Enhancement

This article proposes a multilevel inverter (MLI) based grid-connected solar power transfer unit (PTU). This work is a technological enhancement for the interconnection of photovoltaic (PV) array and distribution grid for mitigating the present energy crisis and power quality issues. The proposed MLI generates nine-level output voltage with a minimum device count and reduced losses. Hence, it provides a low harmonic AC waveform with higher efficiency when compared to the reported topologies. The MLI configuration consists of two isolated DC sources, realized by PV array management in a ratio of 3:1. Eight switches are used in the circuit, out of them, two are bidirectional to achieve the four-quadrant operation and thereby realize the control of reactive power flow. The least number of ON-OFF transitions in high power switches are ensured to minimize the switching losses. The single-stage PTU is controlled to extract the maximum power from PV arrays at varying irradiance levels. The shunt-connected PTU is controlled with an adaptive least mean square algorithm to enhance the grid power quality by meeting the nonlinear local load demands. Three modes of PTU operation are presented in this work according to the available PV power and load power information, and the grid power quality compliance with the IEEE-519 standard is verified in each mode. Battery-supported DC bus voltage regulation is adopted to overcome the reliability issue of the solar PV array power. The proposed system is designed and simulated in MATLAB/Simulink and tested at various operating conditions. Further, the real-time system behavior is tested and validated on a hardware model.

A portable, auxiliary photovoltaic power system for electric vehicles based on a foldable scissors mechanism

In recent years, countries worldwide have actively advocated electric vehicles for environmental protection. However, restrictions on the driving range and charging have hampered the promotion of electric vehicles. This study proposes a portable, auxiliary photovoltaic power system based on a foldable scissors mechanism for electric vehicles. The system includes a photovoltaic power generation module and an electricity transfer module. The photovoltaic power generation module built based on a foldable scissors mechanism is five times smaller than in its unfolded state, improving its portability in its folded state. The electricity transfer module transfers electricity into the cabin via wireless power transfer units and stores electricity in supercapacitors. Solar simulation experiments were conducted to evaluate the system's performance: maximum output power of 1.736 W is measured when the load is 5 Ω, while maximum wireless power transfer efficiency is up to 57.7% with 10 Ω load. An electric vehicle in Chengdu city was simulated for a case study. The results show that the annual output of a single photovoltaic power system can drive the MINIEV for 423.625 km, indicating that the proposed system would be able to supply power for electric vehicles as an auxiliary power supply system.

Throughput performance of a non‐linear energy‐harvesting cognitive radio‐enabled device‐to‐device network

SummaryIn cellular networks, device‐to‐device (D2D) communication is a new paradigm. In this paper, the performance of a non‐linear energy‐harvesting D2D communication network underlaying a cellular network is studied under a channel quality constraint. To make the study more realistic, spectrum sensing is incorporated with the D2D communication. Thus, the user equipments (UEs), that is, D2D devices, are enabled with cognitive radio (CR) technology. Since the UEs are battery powered, there exists an energy constraint. Thus, each UE is also equipped with an energy‐harvesting circuit and harvest energy from radio frequency (RF) signal of power transfer units (PTUs) and cellular users (CUs). Each UE uses its harvested energy for transmission. A D2D transmitter uses sensing information to decide its mode of transmission over a CU channel and is shared in hybrid mode. An algorithm is proposed based on threshold‐based censoring to maximize the throughput. In the proposed scheme, D2D users associated with the bad quality of channels are eliminated from the transmission process. Analytical expressions of throughput and improvement in spectrum utilization (ISU) are developed. The impact of the interference threshold to CU, the censoring threshold and the saturation level of the energy harvester on throughput is studied. The network performance is also investigated for several types of channels. It is found that the amount of fading has a significant impact on throughput performance. It is observed that the proposed scheme outperforms the conventional scheme.

Data analytics using statistical methods and machine learning: a case study of power transfer units

Sensors can produce large amounts of data related to products, design, and materials; however, it is important to use the right data for the right purposes. Therefore, detailed analysis of data accumulated from different sensors in production and assembly manufacturing lines is necessary to minimize faulty products and understand the production process. Additionally, when selecting analytical methods, manufacturing companies must select the most suitable techniques. This paper presents a data analytics approach to extract useful information, such as important measurements for the dimensions of a shim, a small part for aligning shafts, from the manufacturing data of a power transfer unit (PTU). This paper also identifies the best techniques and analytical approaches within the following six individual areas: (1) identifying measurements associated with faults; (2) identifying measurements associated with shim dimensions; (3) identifying associations between station codes; (4) predicting shim dimensions; (5) identifying duplicate samples in faulty data; and (6) identifying error distributions associated with measurement. These areas are analysed in accordance with two analytical approaches: (a) statistical analysis and (b) machine learning (ML)-based analysis. The results show (a) the relative importance of measurements with regard to the faulty unit and shim dimensions, (b) the error distribution of measurements, and (c) the reproduction rate of faulty units. Additionally, both statistical analysis and ML-based analysis have shown that the measurement ‘PTU housing measurement’ is the most important measurement among available shim dimensions. Additionally, certain faulty stations correlated with one another. ML is shown to be the most suitable technique in three areas (e.g. identifying measurements associated with faults), while statistical analysis is sufficient for the other three areas (e.g. identifying measurements associated with shim dimensions) because they do not require a complex analytical model. This study provides a clearer understanding of assembly line production and identifies highly correlated and significant measurements of a faulty unit.

КОНЦЕПЦИЯ РАЗВИТИЯ БЛОКОВ ПЕРЕДАЧИ МОЩНОСТИ В ГИДРОСИСТЕМЕ ГРАЖДАНСКОГО САМОЛЕТА

There is a need to ensure a high level of safety of the aircraft's flight, in particular with regard to the redundancy of the hydraulic system. However, the introduction of additional hydraulic circuits entails, in addition to the advantages and many disadvantages, such as increasing the complexity and weight of the hydraulic system. One of the compromises in this situation was the installation of a power transfer unit. In this article, schematic solutions and peculiarities of operation of power transfer units, cases of their use are considered. An analysis of the current problems and possibilities of improving such aggregates is presented. Possible directions of further development of power transmission units have been identified. In particular, the directions for increasing pressure, reducing the gas content of the liquid, using pump power regulators, reducing gaps, reducing noise and temperatures, and introducing an intelligent component are highlighted. Possibilities for installation of power regulators, their various circuit solutions and operating principles are described. The characteristics of regulators , the operation of which is based on the principle of load sensitivity, the possibility of using these regulators to optimize the operation of the power transfer unit, and, therefore, increase the accuracy, stability, controllability of the entire hydraulic system of the aircraft are presented.

Recursive Domain Decomposition Approach in 2-D Time-Harmonic Wireless Power Transfer Simulations Considering Litz Wires

A recursive domain decomposition approach based on a 2-D time-harmonic finite element (FE) model with AVI formulation is used to model a wireless power transfer (WPT) unit with litz wires. Similar techniques exist in the literature, but they have not yet been applied to WPT units. The approach produces a model that is significantly faster to update and resolve than a traditional FE model, and hence, it is suitable for performing parametric sweeps where the positioning of the coils is varied. Using the technique, it is possible to study losses emerging in individual strands even with an extremely high number of strands. The loss distribution between the litz wire strands is studied, varying the number of strands from 7 to 925. The results and speed are compared with a traditional FE AVI model. The method yields the results up to a 1% relative error compared with the traditional model with significantly faster simulation time.

Finite element modeling and fatigue analysis of hypoid gears installed in a power transfer unit with a correlational study based on an experimental investigation

The effective analysis modeling of a power transfer unit (PTU) with the finite element method was conducted to investigate gear-root bending fatigue. This PTU was designed for an AWD/4WD vehicle system. The hypoid gear plays an important role in PTU systems. The finite element (FE) model is useful to consider various stiffness components and is regarded as the most suitable and effective tool as computer performance increases. Without a proper introduction of system stiffness, we cannot exactly predict fatigue failure life in FE analysis. In this study, a simulation model was developed with the focus of affecting gear-mesh misalignment, such as gear-body flexibility, shafts, bearing stiffness and gearbox stiffness. To validate the results, we did a correlation study of fatigue failure life between physical test results and fatigue life analysis results. Prior to this fatigue analysis, the system torsional stiffness was correlated between physical tests and virtual analysis. Next, loaded tooth contact analysis (LTCA) was conducted to compare the experimental and simulated results. The proposed integrated FE model for predicting the fatigue life of hypoid gear roots based on the full system agrees well with the results of the physical durability test. Moreover, the developed FE model is becoming competitive in terms of computational costs.

A non-contact docking system for charging and recovering autonomous underwater vehicle

To improve the observation capability of the ocean, the combination of the static cabled ocean observatory network and the dynamic autonomous underwater vehicle has attracted more and more attention. In this paper, a non-contact docking system for the autonomous underwater vehicle is developed to combine the advantages of the cabled ocean observatory network and the autonomous underwater vehicle. The system includes both acoustic and optical navigation, underwater wireless communication, non-contact power transfer, and monitoring and controlling of the docking system. This docking system was verified by sea trials at depths of 50 and 105 m. The autonomous underwater vehicle successfully docked 11 times, during which non-contact power transfer and wireless communication were completed. The charging power reached 682 W, with a total efficiency of 78.5%, and the efficiency of the power transfer unit was 92%. The rate of wireless data transfer reached 3.1 MB/s. For the first time, this docking system has realized complete homing and docking navigation, wireless communication and charging in a water depth of more than 100 m, thus establishing a good foundation for the combination of the cabled ocean observatory network and autonomous underwater vehicles.

Chip-Scale Near-Field Resonant Power Transfer via Elastic Waves

This paper reports on the proof-of-concept demonstration of an approach for the synthesis of a through package charging and authenticating communication link enabled by GHz-range aluminum nitride (AlN) piezoelectric transducers. The acoustic link is formed by two thickness-mode acoustic transducers placed on the two sides of a packaging substrate. The link leverages the enhancement of energy transfer that occurs at resonance; 1- $\mu \text{m}$ -thick (2.7 GHz) and 6- $\mu \text{m}$ -thick (500 MHz) AlN acoustic links are demonstrated showing substantial enhancement of power transfer efficiencies (PTE) when using thicker AlN substrates. PTEs of −8 dB at 2.7 GHz and −2 dB at 500 MHz are measured for transducers’ size of $1\times 100\times 100~\mu \text{m}^{3}$ and $6\times 100\times 100~\mu \text{m}^{3}$ through 700- and 500- $\mu \text{m}$ -thick silicon substrates, respectively. The experimental values are in very close agreement with the analytical model of the acoustic link. The potential misalignment between the two transducers is the main limitation of this approach. To overcome this challenge, acoustic phased arrays are devised to enable steering of the transmitted beam. Preliminary results on the steering capability demonstrate about 8 dB of improvement in PTE via a two-element array when dealing with a 100- $\mu \text{m}$ misalignment. This paper is the first step toward the development of next-generation high-efficiency and micro-scale power transfer units that could energize chips through packages. [2017-0010]

Optimal Design of Power Transfer Unit Oil Seal Considering Pressure Drop Generated during Water-Way Driving

This study investigated the pressure drop generated in the power transfer unit (PTU). During water-way driving, this pressure drop could open the lips of an oil seal and caused critical problems, such as water intrusion into or oil leakage out of the PTU. Optimal design of oil seal shape was proposed in order to prevent the unexpected failure of oil seal. As the result of the test to check the effects of the vacuum pressure, it was found that outside water was flowed into inside at - 0.4 bar for dust lip without any interference, whereas, there was no intrusion of outside weater through the seal with interferences of dust lips even at - 0.8 bar. But the seal with interferences of dust lips had 30~40 % higher than that without interference because the interference of dust lip with shaft made friction force increased at the interface between rubber and shaft.

Wireless Power Systems for Mobile Devices Supporting Inductive and Resonant Operating Modes

We demonstrate a family of wireless power devices that operate in a variety of operating modes. A multimode wireless power receiver unit (PRU) allows a mobile device to charge from any one of three wireless power standards: Qi, Power Matters Alliance, or Rezence. A coil arrangement and matching network is introduced that is resonant in both 6.78-MHz and 100-kHz bands, allowing the same power conversion circuitry to operate in either mode. The multi-mode PRU converts 5 W of ac power to a regulated 5-V output with an efficiency of up to 83% in Rezence mode and up to 86% in Qi mode. A wireless charging power transfer unit (PTU) using the Rezence specification charges three such PRUs at a power level of 5 W each with a power transfer efficiency of 66%. An in-band communications protocol provides enhanced capabilities to the Rezence system. Multiple layers of encoding ensure reliable delivery of messages under difficult channel conditions. Another PTU design allows the same receiver to charge through a table of 30-mm thickness while maintaining the in-band communications link. We show that a wide variety of multimode devices are possible, enabling widespread adoption of wireless power even in the absence of a single unified standard.

A Hydraulic Wind Power Transfer System: Operation and Modeling

Conventional wind power plants employ a variable speed gearbox to run a generator housed on top of a tower. A new topology can remove some of the weight from the tower and centralize the wind power generation. This new topology uses a hydraulic wind power transfer system to connect several wind turbines to the generation unit. This paper demonstrates a mathematical modeling of this wind power transfer technology and its dynamic behavior. The flow response, angular velocity, and pressure of the system obtained from the mathematical model are compared with test results to demonstrate the accuracy of the mathematical model. Several speed-step responses of the system obtained from the mathematical model demonstrate a close agreement with the results from the prototype of the hydraulic wind power transfer unit.

NCPX 계측방법을 이용한 타이어/노면 사이에서 발생하는 마찰소음에 대한 차량자체에서 발생하는 소음 제거 연구

PURPOSES : The purpose of this study is to eliminate the noise of the vehicle after measuring the friction noise obtained from the NCPX (Noble Close ProXimity) method. The pure friction noise between the tire and road pavement could be determined from filtering the compositeness of sound and the influence of the vehicle noise. METHODS: The noise magnitude could be determined by analyzing the sound pressure level (SPL) and sound power level (PWL) along with the noise frequency of a FFT (Fast Fourier Transform) analysis as well as CPB (Constant Percentage Bandwidth) analysis. RESULTS: When the test for measuring the friction noise originated somewhere between tire and road pavement is performed with NCPX method, it must be fulfilled by attaching the surface microphone near the tire. In this condition, the surface microphone can measure the friction noise occurred at between tire and pavement, the chassis noise from the engine and power transfer units, the fluctuating aerodynamic noise, and the turbulence noise directly affected to the surface microphone. By using the NCPX method, the noise occurred at the vehicle must be eliminated for measuring the friction noise between tire and pavement from the traffic noise. CONCLUSIONS: The vehicle`s testing engine noise depends on the vehicle and road types. The effect of vehicle`s engine noise is less than the friction noise occurred at between tire and pavement at less than 1% effect.

Development of a Standard Spin Loss Test Procedure for FWD-Based Power Transfer Units

Development of a Standard Spin Loss Test Procedure for FWD-Based Power Transfer Units

An Inductive Link-Based Wireless Power Transfer System for Biomedical Applications

A wireless power transfer system using an inductive link has been demonstrated for implantable sensor applications. The system is composed of two primary blocks: an inductive power transfer unit and a backward data communication unit. The inductive link performs two functions: coupling the required power from a wireless power supply system enabling battery-less, long-term implant operation and providing a backward data transmission path. The backward data communication unit transmits the data to an outside reader using FSK modulation scheme via the inductive link. To demonstrate the operation of the inductive link, a board-level design has been implemented with high link efficiency. Test results from a fabricated sensor system, composed of a hybrid implementation of custom-integrated circuits and board-level discrete components, are presented demonstrating power transmission of 125 mW with a 12.5% power link transmission efficiency. Simultaneous backward data communication involving a digital pulse rate of up to 10 kbps was also observed.

PERFORMANCE OF A POWER TRANSFER UNIT FOR AIRCRAFT APPLICATIONS

This paper considers power transfer between two fluid power circuits such that a failing pressure in one of them is improved by power transfer from the other circuit. The two coupled axial piston machines are effectively driven by the pressure differential across the two machines and particular features are required for the unit to operate successfully. Steady state theory is presented that may be used to select the relative displacement ratios and the range predicted is compared with those typically found in aircraft applications.

High Efficiency Hydraulic Power Transfer Units for Multisystem Aircraft

Fully powered flight controls are common among many aircraft, both military and commercial. Multiple pumps are generally employed to provide these flight controls with a redundant power source in addition to many other aircraft services. The prime hydraulic source in most cases is the engine‐driven pump. It is driven directly by one of the aircraft's engines and offers the most efficient method of converting engine horsepower to hydraulic horsepower. The secondary hydraulic power source is generally not as efficient. It must derive its power from a source other than that which powers the prime pump. Present transport aircraft have utilised bleed air, ram air, electrical power, or hydraulic power to drive this redundant pump. All have demonstrated poor power‐transfer efficiency when compared to a mechanically coupled pump. This inefficiency generally results in increased cost, weight, and complexity to the aircraft. The inadequate performance of existing hydraulic power transfer units was of particular concern. This paper will address the performance problem as well as the Douglas approach to improve it.

Aircraft Power Transfer Units

AS hydraulic systems in modern military and commercial aircraft continue to grow in size and complexity with practically each new aircraft introduced, many aircraft manufacturers are turning to the use of power transfer units to help hold down overall hydraulic system weight and complexity. A power transfer unit allows transfer of hydraulic power from one system to another without transfer of hydraulic fluid (Fig 1).