Lateral Misalignment Research Articles

Nonrotationally symmetric aberrations of off-axis two-mirror astronomical telescopes induced by axial misalignments.

In unobscured off-axis astronomical telescopes with an offset pupil, the effects of axial misalignments are very different from those in on-axis ones. Specifically, a series of nonrotationally symmetric aberrations with characteristic field dependence will be induced by axial misalignments. This paper takes off-axis two-mirror astronomical telescopes as an example to discuss the field characteristics of several important nonrotationally symmetric aberrations (including astigmatism, coma, and trefoil aberration) induced by axial misalignments in off-axis astronomical telescopes. The expressions of these aberrations are derived under some approximations. The accuracy of the proposed expressions is demonstrated. The specific field characteristics of these aberrations are presented and explicated. It is shown that the effects of axial misalignments bear strong similarities to the effects of the lateral misalignments in the symmetry plane of the off-axis system. On the other hand, the inherent relationships between astigmatism and coma induced by axial misalignments are further revealed, which are different from those induced by lateral misalignments. This fact presents the possibility of separating the effects of axial misalignments and lateral misalignments. Most of this work can be extended to other off-axis astronomical telescopes with more freedom.

Analytical solutions for the self‐ and mutual inductances of arbitrary triangular coils with rectangular cross‐section

A new analytical solution for the self- and mutual inductances of arbitrary triangular coils with rectangular cross-section is presented. Firstly, the electromagnetic field problem of a filamentary triangular coil is solved based on second-order vector potential. Then, the solution is effectively extended to the arbitrary triangular coil with different track widths by changing the radius of its inscribed circle. A series of new formulae are given for calculating electromagnetic field, self- and mutual inductances of triangular coils with different shapes, separation distances, lateral misalignments or angular misalignments. Finally, the verification experiments are carried out on a series of irregular and regular triangular coils. Also, the experimental results show that the measured values are in good accordance with the calculated ones.

Distribution of splice loss in single mode optical fiber.

This work investigates a probabilistic model for splice loss in single mode optical fibers. We derive the probability density function for loss values as a function of lateral and angular misalignment. We then use observed data to estimate these model parameters; both Bayesian and maximum likelihood estimation procedures are described. These estimates can then be used to provide an indication of the relative importance of various loss mechanisms. Alternatively, if one is given values for maximum lateral and angular misalignment, our results allow for predictions of expected distribution of loss values. An overall goal of this paper is to demonstrate that, beyond the mean and variance of splice loss, there is significant information in the shape of the distribution of values. A second goal is to understand the trade-off between the number of splice loss measurements and the confidence in estimates of parameters in the splice loss model.

Distributed Diameter Subcoil Twisted Loop Antenna in Nonradiative WPT

This letter focuses on the high-frequency wireless power transfer by electromagnetic induction and its dependence on the lateral misalignment and tilt of the small receiving coil relative to the transmitting coil. We combine two structures, the twisted loop antenna (TLA) and subcoils of a distributed diameter coil (DDC) for transmitting designs. Our system is then referred to as TLA-DDC. The radius of the subcoils is parametrically varied for different distances between the coils and performed in two positions for each distance (coaxial position when the receiving coil is parallel to the plane of the transmitting coil, and center position for the perpendicular orientation of both coils). Then, using different radii for the transmitting DDC TLA when the receiving coil is moved onto its surface allows us to obtain a greater value of efficiency at different positions: up to 2.4 times for the peak value and 1.5 for the average value for receiving coil in parallel plane. The efficiency of the magnetic coupling is determined by means of power efficiency with a comparison between the DDC TLA antennas and a standard coil antenna corresponding to the same inductance value.

Demagnetization Weakening and Magnetic Field Concentration With Ferrite Core Characterization for Efficient Wireless Power Transfer

To improve the power transfer efficiency in wireless power transfer systems, a novel configuration of a magnetic resonant structure is proposed in this paper. According to the analytical expression of mutual inductance, the magnetic field can be improved by weakening the demagnetizing factor for coils with a ferrite core. In this paper, the demagnetizing factors of a cylindrical ferrite core and a novel ferrite core are investigated. Compared with the cylindrical ferrite core, the proposed ferrite core has a smaller demagnetizing factor and an increased mutual inductance. In addition, the magnetic field through the receiving coil is enhanced due to the thin ferrite axis where the magnetic field is concentrated. The proposed ferrite core is designed and analyzed. Moreover, the effects of pitch and lateral misalignment, as well as the number of turns of the receiving coil, the core loss, and the load, are studied. Experimental prototypes are established to validate the performance of the wireless power transfer system with different types of receiving structures. The results indicate that the proposed structure is superior to others and that it shows better performance in power transfer efficiency and transfer distance, which is in good agreement with the theoretical and simulation analysis.

Analysis of Square and Circular Planar Spiral Coils in Wireless Power Transfer System for Electric Vehicles

Nowadays, wireless power transfer (WPT) has attracted great attention from researchers because it is a safe, convenient, and reliable way to recharge electric vehicles. Square and circular coils are most commonly used in WPT systems. However, there are few analyses of comparing these two geometry windings in detail. In this paper, two analytical models of both square and circular planar spiral coils between two semi-infinite substrates are developed based on Fourier–Bessel transformation and dual Fourier transformation. An analytical calculation of the self- and mutual inductance can be carried out with respect to the main parameters of the WPT systems such as the line spacing, the number of turns of the coils and the properties of the substrate. The analytical models can be used to investigate the different tendencies of self- and mutual inductance of square and circular coils, which is helpful for speeding up the design process. Finally, to compare the lateral misalignment tolerance between square and circular coils, a ${{\text{600}}\,\text{mm}\,\times \,{\text{600}}\,\text{mm}}$ with a nominal 200-mm-gap prototype has been built and tested.

Characterization of 3-D Loop Antenna to Overcome the Impact of Small Lateral Misalignment in Wirelessly Powered Intracranial Pressure Monitoring System

This communication presents a 3-D loop antenna to overcome the impact of small lateral misalignment of the order of 2 mm between the inductively coupled antennas. This communication is a continuation of our previously reported work. In our previous work, we have successfully activated the pressure monitoring sensor and performed the pressure readout for an intracranial pressure monitoring application. The pressure sensor was activated through wireless inductive near-field powering. Measurement showed that there was significant effect on pressure readout accuracy due to small lateral misalignment between the inductively coupled antennas. In this communication, we demonstrate that the structural properties of a simple 3-D loop antenna help to overcome the pressure readout error caused by small lateral misalignment. We present the design procedure, simulation results, and pressure readout measurement of the proposed 3-D loop antenna. Moreover, the pressure monitoring system shows maximum improvement of 9 mmHg in pressure readout accuracy with the proposed 3-D loop antenna.

Increase of Sensitivity in 3D Suspended Polymeric Microfluidic Platform through Lateral Misalignment

Increase of Sensitivity in 3D Suspended Polymeric Microfluidic Platform through Lateral Misalignment

Increase of Sensitivity in 3D Suspended Polymeric Microfluidic Platform through Lateral Misalignment

Increase of Sensitivity in 3D Suspended Polymeric Microfluidic Platform through Lateral Misalignment

Analytical calculation of mutual coupling between two misaligned rectangular coils with rectangular cross-section in wireless power applications

An analytic model to calculate the mutual coupling between two misaligned rectangular coils with a wide range of aspect ratios of rectangular cross-section is proposed. The model can analyze all possible layouts of two parallel rectangular coils including coaxial alignment, lateral misalignment, rotational misalignment, and combinations of them. The effects of misalignments, geometry, and cross-sections of rectangular coils are addressed by a single mathematical expression. An experimental setup has been built in order to validate the analytical calculation. Theoretical and experimental results are then compared to verify the effectiveness of the proposed model.

Passive, wireless transduction of electrochemical impedance across thin-film microfabricated coils using reflected impedance.

A new method of wirelessly transducing electrochemical impedance without integrated circuits or discrete electrical components was developed and characterized. The resonant frequency and impedance magnitude at resonance of a planar inductive coil is affected by the load on a secondary coil terminating in sensing electrodes exposed to solution (reflected impedance), allowing the transduction of the high-frequency electrochemical impedance between the two electrodes. Biocompatible, flexible secondary coils with sensing electrodes made from gold and Parylene C were microfabricated and the reflected impedance in response to phosphate-buffered saline solutions of varying concentrations was characterized. Both the resonant frequency and impedance at resonance were highly sensitive to changes in solution conductivity at the secondary electrodes, and the effects of vertical separation, lateral misalignment, and temperature changes were also characterized. Two applications of reflected impedance in biomedical sensors for hydrocephalus shunts and glucose sensing are discussed.

Low-loss, broadband and high fabrication tolerant vertically tapered optical couplers for monolithic integration of Si3N4 and polymer waveguides.

A low-loss, broadband and high fabrication tolerant optical coupler for the monolithic integration of Si3N4 and polymer waveguides is designed and experimentally demonstrated. The coupler is based on the adiabatic vertical tapering of the Si3N4 waveguides. Low-loss operation is experimentally verified at both 976 and 1460-1635nm wavelengths. Measured losses per coupler are as low as 0.12 and 0.14dB at 976 and 1550nm, respectively, and below 0.2dB at both wavelengths for lateral misalignments between the Si3N4 and polymer waveguides up to 1.0μm.

Misalignment Sensitivity of Strongly Coupled Wireless Power Transfer Systems

A traditional strongly coupled magnetic resonance (SCMR) system is highly sensitive to the alignment between the transmitter and receiver elements, which is an issue that has limited their applicability in practical wireless power transfer systems. This paper proposes, for the first time, a novel set of SCMR-based topologies that are less sensitive to misalignment while providing large wireless powering efficiencies. Specifically, instead of using planar coils for the transmitter and the receiver, we connect two orthogonal coils together into a 3-D model to provide misalignment insensitivity. Three SCMR systems (standard SCMR, conformal SCMR, and hybrid SCMR systems) are studied and compared to the proposed 3-D SCMR system in terms of angular azimuth, angular elevation, and lateral misalignment. Also, the ranges of these SCMR systems are compared. It is shown that the proposed misalignment system achieves above 40% efficiency for the entire range of 360° of angular misalignment. Also, our results show that the proposed misalignment system provides longer range.

Coupling-based Huygens' meta-atom utilizing bilayer complementary plasmonic structure for light manipulation.

Huygens' meta-atom is the basic building unit of Huygens' metasurfaces allowing for almost arbitrary wavefront shaping across a surface. We here present a kind of Huygens' meta-atom by coupling a nanodisk to its Babinet-complementary structure (nanohole), and develop an optical lumped nanocircuit model to analyze vertical and lateral coupling effects and resonance frequencies. Simulation results show that the tuned coupling via lateral misalignment between the two nanostructures is sufficient to shape the wavefront without changing the dimensions or orientations of antennas. By tuning the coupling via lateral misalignment, we design a reflective gradient metasurface based on one coupled mode and a high-efficiency transmissive gradient metasurface working in the spectral overlap of electric and magnetic resonances to realize beam deflection. The proposed coupling-based Huygens' meta-atom is a new building block for plasmonic metasurfaces with enhanced light-matter interactions, high-efficiency and almost arbitrary wavefront shaping over the full electromagnetic spectrum.

Position and Angular Misalignment Analysis for Implantable Wireless Power Transfer System Based on Magnetic Resonance

As a widely-acknowledged truth, the interval of human tissue, the breathing activity, and the body motion work together to change the relative position of the antenna. This knowledge, with detailed examination, is going to bring significant change to the transmission efficiency in the implementation of human wireless power transfer. This paper focused on the relationship of the transfer efficiency with lateral distance, vertical distance and angular (around the center and along the edge) misalignment. A new formula, which serves to connect the geometrical parameters both with the self-resonance frequency and with the Q-factor of the printed circuit board antenna, was given. Furthermore, the paper gave a significant analysis of the efficiency with lateral distance change, vertical distance change and two kinds of angular misalignments using finite element method. The experimental results showed that in the situation of vertical distance change and angular (along the edge) misalignment, the transmission efficiency drops rapidly with the displacement of antenna. However, in the situation of lateral distance change and angular (along the edge) misalignment, there were a high-efficiency distance—the lateral misalignment ≤40% of the length of the width in the lateral misalignment; and a high-efficiency angle—angular around the center misalignment ≤30o in the angular misalignment. Within the ranges, a high-efficiency space (HES) is formed in the implantable WPT system utility, and the transmission efficiency drops rapidly when the antenna is beyond the HES. This paper can provide a practical application to the antenna design and specific implementation in human implantable WPT system.

Design approach for a wireless power transfer system for wristband wearable devices

In this study, the design approach for wireless power systems in the application of charging wristband wearable devices is studied. As the power transfer efficiency relates to the system parameters, the design approach includes an analytical model for available wireless power in planar circular coils with lateral and angular misalignments, which is typically the case in these applications. The model is then utilised in an optimisation algorithm to design the wireless power system such that maximum available power is transferred through the system. The practicality of the proposed wireless power transfer (WPT) system design is analysed in terms of positioning the power transmitter coil on a bed, while performing the power transfer during a sleeping period of the wearer. Experimental results validate the analytical model of mutual inductance variations and demonstrate the performance of the WPT system for this application.

A Dynamic EV Charging System for Slow Moving Traffic Applications

Inductive power transfer (IPT) is by far the most popular method to transfer energy wirelessly and has attracted considerable attention in recent times. The Wireless Power Consortium has developed a standard (Qi) for low power consumer electronics, whereas the Society of Automotive Engineers (SAE) is working on a standard (J2954) to charge electric vehicles (EVs) wirelessly. SAE’s current efforts are focused only on transferring power to the vehicles at rest (static), whereas no work has been done so far on developing the standards for transferring power to the vehicles on the move (dynamic). This paper presents the magnetic design of an IPT system for a dynamic EV charging application, to continuously deliver a power of 15 kW to an EV, along the direction of travel within the lateral misalignment of ±200 mm. The experimental validation of system operation, however, was conducted at 5 kW. The design aims at distributing the cost and complexity of the system between the primary and secondary sides, while achieving a smooth power transfer profile. In addition, the system is designed to exploit the shielding effect provided by the vehicle, as the field generating components of the system are covered by the vehicle body under all operating conditions.

Image restoration in fiber-coupled imagers using space-variant impulse response characterization.

Fiber-coupled image sensors have attracted interest in recent years for high-resolution conformal image transfer, including mapping of the spherical image surface of a monocentric wide-angle lens to one or more flat focal plane sensors. However, image resolution is lost due to fiber bundle defects, moiré from lateral fiber-sensor misalignment, and blur due to the nonzero gap between fiber bundle and the image sensor. Here we investigate whether subpixel impulse response characterization of the strongly shift-variant impulse response can be used with existing image-processing techniques to recover the resolution otherwise lost in image transfer. We show that the submicrometer impulse response is experimentally repeatable, and can be used to recover image data and reveal fine features of the input surface structure of a 2.5 μm pitch fiber bundle.

Pneumatic Muscle-Actuated Adjustable Compliant Gripper System for Assembly Operations

The aim of this paper is to present and discuss an innovative, constructive solution for a gripper system that can be attached to an industrial robot for assembly operations. The construction of this gripper system is based on a linear pneumatic muscle used as the actuator and the transmission of motion by gear-and-rack mechanisms. Air compressibility renders pneumatic muscle behaviour inherently compliant; this favours automated assembly applications as it allows the correction of inevitable lateral and angular misalignments in mating operations. Therefore, the jamming of a peg-like object can be avoided when this is introduced into a hole with tight clearance. In addition to the construction of the gripper system, this paper discusses its actuation, as well other characteristics.

Investigation of Unequal Planar Wireless Electricity Device for Efficient Wireless Power Transfer

This article focuses on the design and investigation of a pair of unequally sized wireless electricity (Witricity) devices that are equipped with integrated planar coil strips. The proposed pair of devices consists of two different square-shaped resonator sizes of 120 mm × 120 mm and 80 mm × 80 mm, acting as a transmitter and receiver, respectively. The devices are designed, simulated and optimized using the CST Microwave Studio software prior to being fabricated and verified using a vector network analyzer (VNA). The surface current results of the coupled devices indicate a good current density at 10 mm to 30 mm distance range. This good current density demonstrates that the coupled devices' surface has more electric current per unit area, which leads to a good performance up to 30 mm range. Hence, the results also reveal good coupling efficiency between the coupled devices, which is approximately 54.5 % at up to a 30 mm distance, with both devices axially aligned. In addition, a coupling efficiency of 50 % is achieved when a maximum lateral misalignment (LM) of 10 mm, and a varied angular misalignment (AM) from 0° to 40° are implemented to the proposed device.