Misalignment Tolerance Research Articles

A Quadrupole Receiving Coil With Series-Connected Diode Rectifiers for Interoperability of Nonpolarized and Polarized Transmitting Coils

Non-polarized and polarized coils are utilized in an electric vehicles (EV) wireless charging system. These coils are decoupled from each other at the central position, leading to interoperability issues. This letter proposes a new decoupling method and a quadrupole receiving coil with series connected diode rectifiers for interoperability purposes. Decoupling windings are added to achieve decoupling of the four receiving poles. The total mutual inductance between the transmitting coil and the quadrupole receiving coil is the summation of the absolute values of the mutual inductances between the transmitting coil and the four receiving poles. In this way, the proposed quadrupole coil can be tolerant with not only the non-polarized transmitting coil, but also with the polarized transmitting coils along two perpendicular directions. The experimental results confirm that a large coupling and efficient power transfer can be achieved with the non-polarized coil and the polarized coil placed at two perpendicular directions with good misalignment tolerance.

A universal wireless charging platform with novel bulged‐structure transmitter design for multiple heterogeneous autonomous underwater vehicles (AUVs)

AbstractAutonomous underwater vehicles (AUVs) are important mobile equipment for ocean observation. Subsea docking stations are used to charge AUV batteries to increase their cruise duration. Here, a universal wireless charging platform with a novel transmitter is developed to address the issues of poor compatibility existing in conventional docking stations. In order to guarantee a sufficient charging area and reduce copper losses, the proposed transmitter is designed to have a bulged‐structure surrounding coil and a centre coil in coaxial. Moreover, the parameters of the transmitter that impact the magnetic flux density are analysed and optimized by non‐linear programming by Quadratic Lagrangian (NLPQL) algorithm to achieve a field with desirable intensity and uniformity. The characteristics of the circuits under single‐load and double‐load conditions have been tested in air and tank experiments. The results verify that the proposed platform achieves both the universality and misalignment tolerance requirements.

Design of a Highly Compatible Underwater Wireless Power Transfer Station for Seafloor Observation Equipment

Conventional cabled seafloor observatories (CSOs) power in-situ instruments via wet-mated or dry-mated direct electrical contact (DEC) connectors to achieve long-term and real-time observation. However, the DEC connectors have high risks of water leakage and short circuits in power feeding, especially under high water pressure. This paper proposes a highly compatible underwater station based on inductive wireless power transfer (IPT) technology to address the above reliability issue. A novel energy transmitter with runway-structure coils is applied to the proposed underwater station to cover a sufficient power feeding area so that various in-situ equipment can be powered with desirable misalignment tolerance. The magnetic field distribution is analyzed by both derivation and finite element analysis (FEA) methods, and the principal parameters of the transmitter are further optimized and compared with both the mixed-integer sequential quadratic programming (MISQP) algorithm and the evolutionary algorithm (EA) for better performance. The same results show a reliable optimization process. The WPT circuit characteristics are also investigated to power different loads and improve the power transmission efficiency. The output power decreases, and the transmission efficiency rises and then decreases as the load increases. In addition, receivers with higher mutual inductance have better transmission performance. A prototype of the underwater station has been tested both in air and in water, and the experimental results have proven it can power multiple seafloor observation instruments stably and achieve compatibility requirements. The maximum output power of the station prototype for testing is 100 W, and the maximum overall transmission efficiency is 61%.

A simplified laser-to-chip edge coupling scheme using 3D SU-8 taper

In this work, we design and simulate a three-dimensional (3D) SU-8 tapered edge coupler for effectively guiding light from an edge-emitting semiconductor laser diode directly to a silicon waveguide to realize a hybrid on-chip silicon light source. A series of coupling efficiencies for the commonly used top silicon thicknesses of the silicon-on-insulator wafers from 220 to 3000 nm are obtained, showing that this polymer taper can largely improve the coupling efficiency when the silicon waveguide thickness is moderate, for instance, from 41% (with no taper) to 67% for the 700 nm- thick silicon waveguide under 1 μm gap offset and relax the lateral misalignment tolerance to above one micron by suppressing the butt refractive index contrast and the mode mismatch between the laser diode and the silicon waveguide. Wave transformation inside the tapered coupler and the input silicon waveguide has also been revealed by 3D finite-difference time-domain simulations. This 3D tapered coupler is cost effective and easily fabricated which can have wide practical applications in massive production of various silicon photonic chips based on the present complementary metal-oxide-semiconductor foundry.

An Antioffset Electric Vehicle Wireless Charging System Based on Dual Coupled Antiparallel Coils

Wireless power transfer (WPT) has the advantages of safety, convenience and freedom from the impact of the environment. Misalignment tolerance is a major issue for the electric vehicle wireless charging system. In this letter, a WPT system with anti-offset characteristic is proposed based on dual coupled transmitting coils with antiparallel windings, forming the inductor-capacitor-capacitor-series (LCC-S) topology. The T-shaped equivalent circuit is developed to obtain the decoupling circuit. Based on the misalignment tolerant characteristic of the antiparallel windings, the two transmitting coils are designed to have the same coil structure with antiparallel windings, leading to the same variation trend of the coupling between the two transmitting coils and the receiving coil and the opposite influence on the output. Therefore, the output voltage can be stable within a certain misalignment range. An experimental prototype is built to verify the effectiveness of the proposal. The experimental results show that the output voltage can remain stable within the range of −150 mm to 150 mm in the horizontal direction and 80 mm to 160 mm in the vertical direction.

Achieving misalignment tolerance with hybrid topologies in electric vehicle wireless charging systems

With the rocketing progress of wireless power transfer (WPT) for electric vehicles (EVs), the issue of misalignment tolerance has become increasingly vital, a hybrid topology of the series–series (S–S) and inductor–capacitor–capacitor-parallel (LCC-P) is proposed in this paper to achieve misalignment tolerance. Both the S–S topology and the LCC-P topology have constant-current output, the difference is that the output power of S–S increases with the increasing misalignment, oppositely, the output power of LCC-P reduces with the increasing misalignment. A combination of these two topologies can enhance the anti-offset capability. The magnetic couplers utilize unipolar (Q) and bipolar (DD) coils as the two decoupled coils for power transfer. The mathematical model has been established and analyzed. The transfer efficiency and the output parameters’ expressions of current, voltage and power have been derived. The theoretical analysis has been verified in the simulation model of MATLAB/Simulink. The proposed hybrid topology has succeeded in achieving misalignment tolerance.

Comprehensive investigation on misalignment tolerance of inductive power transfer systems

Inductive power transfer (IPT) technology is gaining popularity for wireless charging applications of future electric charging for its contactless power supply. The square and circular planar spiral coils are most widely used in wireless power charge due to its simple structure. This paper gives analyses of comparing these two geometry windings in detail. As for an inductive power transfer system, coupling structures, such as line spacing and magnetic core structure, are of paramount importance, because of their significant impact on power transfer efficiency and voltage stability. By analyzing the characteristics of magnetic field distribution of the coupler, influences of coil shape, size, line spacing and core structures on coupling coefficient and coupling coefficient retaining ratio (CCRR) are firstly investigated. Misalignment tolerance under different coupler structures is then conducted, comprehensive optimization schemes of misalignment tolerance improvement are proposed. Results show that for the coupling coefficient and coupling coefficient retaining ratio, the optimal line spacing and core structures are highly dependent on the coil shape, size and air gap. A 3-kW IPT system was also built and experimental validations on original and optimized structures are performed. And the better misalignment tolerance was achieved with the optimal line spacing, transmitting coil and ferrite core structure.

An input‐parallel output‐series wireless power transfer scheme for automatic vehicle modular and misalignment‐tolerant charging

SummaryFor ameliorating the energy pick‐up capability of wireless charging during the movement of automatic vehicles, this paper proposes an input‐parallel output‐series wireless power transfer (WPT) scheme with modular extension and misalignment tolerance. Dual inductor‐capacitor‐capacitor (LCC) and series capacitor compensated WPT channels are included in this scheme. Input ports at the transmitter (Tx) side are in parallel, which shares an identical voltage source, and output ports at the receiver (Rx) side are in series for modular expansion of output capacity. Asymmetrical coupling coils based on the magnetic field distribution optimization of Tx coils are employed in this design for the tolerance performance under Rx misalignments. An output voltage control method at the Tx side is implemented to regulate the output voltage of each channel without communication. The phase and amplitude of each channel's output are actively consistent through the control, thereby improving the WPT efficiency and avoiding channel damage due to excessive output. Finally, a scaled‐down WPT prototype is established, and the performance of the proposed scheme is verified by experimental results.

An LCC‐S compensated wireless power transfer system using receiver‐side switched‐controlled capacitor combined semi‐active rectifier for constant voltage charging with misalignment tolerance

AbstractThe output characteristics of wireless power transfer systems are strongly susceptible to coupling and load variations. To achieve a constant voltage output under varying coupling and load, a voltage regulation method based on a combination of a semi‐active rectifier (SAR) and a switched‐controlled capacitor (SCC) is proposed for the LCC‐S topology. Adjusting the SAR can effectively regulate the voltage, and the introduction of SCC compensates the impedance brought by SAR, ensuring that the resonance condition is fully satisfied at the receiver side. Thus, the proposed wireless power transfer system can achieve zero phase angle over the entire load and coupling range, minimizing reactive power losses. This control method only needs to collect the signal from the receiver side, which enables single‐side control as well as avoids the wireless communication. The situation of coupler parameter drift due to misalignment is also considered. Even if the self‐inductance changes, the zero phase angle can be guaranteed on the receiving side by adjusting the SCC, and the zero voltage switching of the transmitter side can still be achieved. The principle prototype of 3 kW is constructed and the experimental results prove the effectiveness of the proposed method.

Requirements and Solutions for Robust Beam Alignment in Fiber-Coupled Free-Space Optical Systems

The continuous growth of Internet data traffic is pushing the current radio-frequency wireless technologies up to their physical limits. To overcome the upcoming bandwidth bottleneck, Free-Space Optics (FSO) is currently deemed as a key breakthrough toward next-generation ultra-high-capacity wireless links. Despite its numerous advantages, FSO also entails several particular challenges regarding the mitigation of the stochastic impairments induced by turbulence and the strict alignment requirements. One of the main issues of FSO communication systems is the mitigation of pointing errors and angle-of-arrival (AoA) fluctuations, which arise from misalignments induced by atmospheric turbulence and vibrations at the transmitting and receiving stations. A common approach to mitigate the impact of pointing errors is the use of an acquisition, tracking and pointing (ATP) system on one or both ends of the FSO link. In this paper, we present a characterization of the pointing errors and the AoA impact on the power budget of the FSO link to quantify the misalignment impairments. Afterwards, we experimentally demonstrate an FSO link with an ATP mechanism at both ends, managed by a control plane that enables the continuous and accurate alignment of the FSO link. To increase the misalignment tolerance, the ATP mechanism comprises two stages: the first one is based on a spatial diversity method provided by a quadrant detector, while the second stage maximizes the optical received power. Lastly, the impact of the beam misalignment on the achievable information rate of a coherent optical wireless system is theoretically addressed and characterized.

Compact Z-Impedance Compensation for Inductive Power Transfer and its Capacitance Tuning Method

This article proposes a Z-impedance compensation for inductive power transfer (IPT). There are three contributions. First, a Z-impedance-S compensated IPT topology is developed to achieve constant transmitting current, load-independent constant-voltage output, and zero-phase angle (ZPA) property, which is an alternative to the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S topology. Second, compared to an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> circuit, the Z-impedance compensation burdens much smaller current/voltage stress and shows lower sensitivity to compensation capacitance drift, contributing to high-power applications. Third, a capacitance tuning method is proposed to regulate power, which improves the misalignment tolerance. Two 5 kW Z impedance-S and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S IPT prototypes are implemented. Experiments show that the Z-impedance-S IPT system achieves comparable power and efficiency with an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> -S IPT system with smaller current/voltage stress and lower sensitivity. The proposed capacitance tuning method is effective to maintain a rated 3 kW output within a horizontal misalignment of [0 100 mm] with zero-voltage-switching and ZPA operation. Meantime, A peak dc-dc efficiency of 96.88% is realized in the Z impedance-S IPT system at 3.47 kW.

An Unsymmetrical Driving Scheme for Inductive Power Transfer Systems Using Decoupled Transmitter Coils

This paper explores a novel and unsymmetrical driving scheme for an inductive power transfer system using decoupled transmitter (TX) coils. Instead of driving each TX in the same way, the proposed driving scheme would employ various compensations for different coils. When one TX coil is series compensated, the other TX coil is compensated by the LCC network, and these two compensated coils are driven by a cascaded inverter instead of two bridge ones. Through circuit analysis, the power flow of each TX is closely coupled and help avoid over load conditions. Meanwhile, it would maintain the benefits of a multiple-TX system like high misalignment tolerance, and enable the system design and control like a single-TX one, e.g., having load-independent output voltage and optimal loads. The experiment demonstrates the waveform of normal mode and protection mode, load-independent output voltage, power distribution conditions, and the optimum efficiency.

Free-Rotation Wireless Power Transfer System Based on Composite Anti-Misalignment Method for AUVs

In the underwater environment, the ocean current will have a great influence on the anti-misalignment performance of the wireless power transfer (WPT) system for the autonomous underwater vehicles (AUVs). In this letter, a free-rotation WPT system with a new magnetic coupler for AUVs is proposed to improve the rotational and axial misalignment tolerance. The magnetic coupler has two decoupled transmitters and one segmented arc solenoid receiver with reversely wound adjacent receiver coils. The mutual inductances between the receiver and the two transmitters can compensate each other. Moreover, cooperated with the phase control between the two transmitters, the system can achieve more stable output power under the rotational and axial misalignment. A free-rotation WPT prototype was set up and the experimental results showed that the output power can reach 700 W and the output power fluctuation is below 5% based on the proposed anti-misalignment method.

A Misalignment Tolerate Integrated S-S-S-Compensated WPT System with Constant Current Output

This paper proposes a cooperative (Cx) coil design for the series-series-series (S-S-S)-compensated wireless power transfer (WPT) system to improve the horizontal misalignment tolerance and the system efficiency. The Cx coil is formed by four series-connected rectangular coils and integrated into the transmitter (Tx) coil to provide a coupling variation opposite to that of the Tx coil, obtaining the constant equivalent mutual inductance (MI). The design overcomes the problem that the decoupling-designed intermediate coil does not participate in system energy delivery under the well-aligned condition. A misalignment tolerant design with the zero-phase-angle (ZPA) input and load-independent constant current (CC) output conditions is presented based on the Delta-Wye network transform and linear regression. A comparison between the proposed design and a two-coil system using a similar amount of copper, i.e., the Tx coil plus the Cx coil, is made. Finally, a 218.08 W/85.85 kHz scaled-down prototype with the proposed Cx coil is demonstrated to validate the performance and effectiveness of the design. The proposed design can maintain at over 82% efficiency, and offer the ZPA input and load-independent CC output within a misalignment tolerant range of 50% of the length of the receiver coil, as the load varies from 10 Ω to 25 Ω.

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

The Fifth Bioelectronic Medicine Summit Hosted by the Feinstein Institutes for Medical Research (Manhasset, NY) and Columbia Engineering (NY, NY) at The Garden City Hotel, Garden City, NY 11530 on October 11-12th, 2022- Bioelectronic Medicine: Today’s Tools, Tomorrow’s Therapies

Multi-Objective Optimization of LCC-S-Compensated IPT System for Improving Misalignment Tolerance

Due to their excellent performance, the inductor–capacitor–capacitor-series (LCC-S)-compensated topologies are extensively used in inductive power transfer (IPT) applications. However, perfect alignment of the system’s contactless couplers is difficult, which leads to serious deterioration of the system output characteristics. In this paper, the influence of the coupler misalignment on the performance of the conventional resonant system is studied. To obtain stable output against varying couplings and loads in a certain range, a novel parameter design method based on the multi-objective particle swarm optimization (MOPSO) algorithm is introduced. The multi-objective optimization framework is developed to analyze the Pareto trade-offs between three conflicting performance metrics, namely output current/voltage ripple, reactive power transmission and component stress. Optimization results depict that misalignment tolerances in both constant current output (CCO)-type and constant voltage output (CVO)-type LCC-S-compensated IPT systems are improved, while a wider load range is suitable for a CCO-type system using the method of compensation parameter optimization. Experimental results are highly consistent with the design, achieving a current fluctuation of no more than 10.5% with a load range from 50 Ω to 100 Ω and a voltage fluctuation of less than 10.4% with a narrow load from 90 Ω to 100 Ω over 100% of coupling variations (from 0.25 to 0.5).

Enhancing Power Transmission Stability of AUV’s Wireless Power Transfer System with Compact Planar Magnetic Coupler

In this paper, a wireless power transfer (WPT) system with a compact planar magnetic coupler for an autonomous underwater vehicle (AUV) is proposed. A passive induction (PI) coil is integrated into the circular transmitter (Tx) coil to build a uniform magnetic field (UMF), which can guarantee the stable output of the WPT system under uncertain radial and axial misalignments for AUV. Based on normalized magnetic induction intensity distribution analysis, a UMF constructing method with a PI coil is given, aiming to eliminate the fluctuation of magnetic field intensity, and the PI coil design principles and flow chart are obtained. The theoretical analysis shows the proposed integrated coil can effectively enhance the radial misalignment tolerance compared with a conventional circular spiral coil. The zero-phase angle (ZPA) input condition can be achieved by adjusting the series capacitor connected with the Tx coil in S-S compensation topology. Experimental results show that the proposed magnetic coupler containing an integrated coil significantly improves the stability of output power and power transfer efficiency within the possible radial and axial misalignments compared with a conventional coupler. It was demonstrated that the output power changes less than 5.5% and the power transfer efficiency maintains at approximately 84.5% in arbitrary radial positions within the possible working region with an axial transfer distance of 50 mm in saltwater.

Operation of Inductive Charging Systems Under Misalignment Conditions: A Review for Electric Vehicles

Inductive power transfer (IPT) for electric vehicles (EVs) is an emerging technology that can transfer power wirelessly over certain distances, thus offering some remarkable characteristics in terms of flexibility, position, and movability. The output power of an IPT system depends on the coupling factor of the magnetic couplers, which can deviate from the nominal operating conditions due to the occurrence of misalignment. Nevertheless, misalignment of the magnetic couplers in inductive charging is inevitable, and it usually results in the variation of the mutual inductance and output power of the system with a corresponding decrease in the system’s overall efficiency. So far, the literature has reported various techniques for achieving designs with higher misalignment tolerance. The reported techniques can be mainly classified into three categories, as viewed from the following aspects: magnetic couplers layouts, compensation networks, and control strategy. Each of these techniques has its pros and cons in terms of implementation cost, system layout, efficiency, power density, and reliability depending on the application. With the increased investigation of more applications of IPT, new modified techniques for improving the misalignment tolerance in the IPT system are continuously being proposed based on permutations and combinations of the existing ones; thus causing some confusion and difficulties for researchers and system vendors to follow. This article, therefore, aims to provide a comprehensive review of the existing methods for IPT systems that address the misalignment issue in EVs’ wireless charging. The background of the inductive charging systems for EVs is presented and an investigation of the numerous factors affecting the output power and other performances is conducted. In addition, the advantages and disadvantages of each technique on the IPT system’s performance are analyzed in detail.

A Systematic Method for Efficient Wireless Powering to Implantable Biomedical Devices

Wireless power transfer (WPT) technology has played a vital role in the rapid development of biomedical devices. While several single methods to improve WPT efficiency have been reported, the lack of integrality in these single methods limits the effect of the improvements. In this investigation, we analyze the physical process of a typical WPT scenario and find that the high propagation loss consisting of in-tissue attenuation and interface reflection degrades the WPT performance. A systematic method to comprehensively improve WPT efficiency is then proposed. Specifically, a Fresnel zone plate (FZP) is applied against the attenuation of inner biological tissue, and a practical air layer-artificial matching layer (AL-AML) is applied to decrease the reflection on the surface of biological tissue. According to a simulation of possible analytical models, the efficiency is significantly improved when using the proposed method. In an experiment with an implant depth of 20 mm, the proposed systematic method is found to enhance maximum relative received power by 12 dB, with an almost 15-fold increase in efficiency over the conventional system with just a transmitter (Tx) and a receiver (Rx). It is also verified that the improvement in efficiency is greater in the systematic method than in single methods. Also, various misalignment tolerances between the proposed structures and the Rx are determined from the coupling strength of the proposed WPT system. The results of this investigation show the potential of the proposed systematic method for further improvements in WPT efficiency.

An Onboard Magnetic Integration-Based WPT System for UAV Misalignment-Tolerant Charging With Constant Current Output

This article presents an onboard magnetic integration-based wireless power transfer (WPT) system for misalignment-tolerant and stable charging of unmanned aerial vehicles (UAVs) with a lightweight and compact receiver (Rx). The onboard Rx and integrated compensation coils are coupled with an asymmetrical transmitter (Tx) coil to enhance the power transmission capacity and achieve misalignment tolerance. The secondary integrated-based compensation topology and its tuning method, which neutralize the coupling between the Rx and compensation coils, are elaborated to maintain the high-order topology performance with zero phase angle (ZPA) and constant current (CC) output. Furthermore, the topology operates stably in the whole misalignment-tolerant area of the asymmetrical coils. Finally, a WPT prototype is built to verify the performance of the studied methodology in both load variation and position deviation configurations. The output current changes by only ±2.5% when the load resistance varies from 5 to 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> . The proposed onboard magnetic integration-based WPT system allows ±150-mm landing deviations of UAVs.