Misalignment Distance Research Articles

82‐1: Distinguished Paper: Geometric Distortion on Video See‐Through Head‐Mounted Displays

We evaluate the geometric distortion on video see‐through (VST) head‐mounted displays (HMDs) with single‐camera and dualcamera design. We present the experimental setup and metrology for geometric calibration and VST geometric distortion measurement. Physical geometric distortion is compared to the distortion of digital content on a VST HMD. We investigate the impacts of camera misalignment and depth distance on VST geometric distortion with angular‐based distortion correction.

Geometric distortion on video see‐through head‐mounted displays

AbstractVideo see‐through (VST) head‐mounted displays (HMDs) reconstruct the physical world using outward‐facing cameras and depth sensors. One of the major challenges for VST HMDs is the geometric distortion of the physical pass‐through content. In this study, we present the experimental setup and metrology for VST geometric distortion measurement on single‐camera and dual‐camera VST HMDs. The VST geometric distortion is compared to the digital distortion by the HMD. Finally, we investigate the impacts of camera misalignment and depth distance on VST geometric distortion without and with angular‐based distortion correction. The results demonstrate that camera misalignment with respect to the eye position is the primary root cause for the distortion. Dual‐camera setup is necessary to minimize the VST geometric distortion by placing the cameras close to the eye positions. Although distortion correction can partially mitigate VST geometric distortion in a 2D plane, it remains a challenge for VST distortion correction at multiple depth distance in the 3D space. The method and findings presented of this study may provide guidelines for evaluation of spatial accuracy on VST HMDs and hardware design.

Realization of Unity Power Factor Wireless Power Transfer System under Subnormal Operation Conditions

The power factor of wireless power transfer system, determined by its compensation network part, is easily affected by parameter detuning, coil misalignment, and load variation. In this paper, a mathematical model for the compensation network part is established. Theoretical analysis shows that the inverter part can be considered as a negative resistor by deducing the inherent static-state frequency solution of the compensation network part. Therefore, the unity power factor wireless power transfer system can be maintained under any possible operation conditions by tracking the inherent static-state frequency solution. More importantly, no digital controller or parameter identification or information interactions between the primary and secondary coils are needed during the tracking process. Compared with previous unity power factor realization methods, the proposed tracking strategy has the advantages of fewer sampling variables, a faster response time, and a simpler regulation process. Finally, an experimental platform is built to test the practical performance of the proposed tracking strategy under many subnormal operation conditions. Our experimental results show that approximate unity power factor can be realized at 10–15 cm coil misalignment distance and 30–90 Ω load variation range.

Spatial Azimuthal Misalignment Characteristics of High-Temperature Superconducting Wireless Power Transmission Systems

Magnetically coupled resonant wireless power transmission technology (WPT) based on high-temperature superconducting (HTS) coils has gained wide popularity due to its low impedance and high-quality factor Q value characteristics. This technology has greatly improved the energy transfer performance of wireless power transmission (WPT) systems. However, practical applications of conventional WPT, such as wireless charging of autonomous underwater vehicles at mooring points, often encounter spatial misalignment issues due to the complex ocean environment and ocean currents. Nonetheless, few studies have investigated the spatial misalignment of HTS WPT systems, particularly the angular misalignment. This paper presents a solution to address this problem by constructing magnetically coupled resonant wireless energy transmission systems based on HTS coils and copper coils. The study analyzes the relationship between the transmission efficiency of the WPT system and the received power of the load with respect to the spatial orientation of the coil. The performance of the superconducting coil and copper coil WPT systems is compared. The experimental results demonstrate that, under the same spatially misaligned conditions, the WPT system using HTS coils can significantly improve the transmission efficiency and load power compared to the conventional copper WPT system. Moreover, simultaneous adjustment of the lateral misalignment distance and different orientation deflection angles can improve the transmission efficiency and smooth load output power of the high-temperature superconducting WPT system.

Characteristics analysis of resonance-based wireless power transfer using magnetic coupling and electric coupling

This study analyses the wireless power transfer of the resonance-based magnetic coupling method and resonance-based electric coupling method and provides information about the characteristics of each. To compare the characteristics of each method, the power transfer efficiency was analysed according to the transfer alignment and misalignment distance between the transceivers. More specifically, they were theoretically analysed through equivalent circuit models, and the results were verified through electromagnetic numerical analysis simulation and the fabrication and experimental results of a wireless power transfer coupler. Although both methods differ according to the coupling method, in terms of power transfer efficiency, it was found that they are determined by the same physical phenomena. Furthermore, in both methods, a null-power point occurred during misalignment between the transceivers. The misalignment distance within which the null-power point occurred is intrinsically determined by the structure of the resonant coupler.

Improvements of PV receiver in laser wireless power transmission by non-imaging optics

Laser Wireless Power Transmission (LWPT) systems have an extensive prospect in the field of wireless energy transmissions such as the space control on-orbit, spacecraft sensor networks, satellites to satellite communication and power transmission, ground to ground, ground to air, ground to Unmanned Aerial Vehicle (UAV), etc. Previously, Concentrated Photovoltaics(CPV) has been used in solar energy as a solution to lower the size of the photovoltaics and yet increase efficiency. As is known laser beam spot normally presents a Gaussian distribution and laser somehow must match the size of the PV cell or array, that is how lens and concentrators are important to reshape and guide the laser beam towards the photovoltaics and in case of misalignment. The current research aims at improve the output performance of LWPT receiver by typical non-imaging optical device-Cross Compound Parabolic Concentrator (CCPC), which helps to improve the transmission of laser beam from different incident directions. Multi-field characteristics of the CPV module under laser power would be solved based on parameters from non-linear regression and experimental study. The multi-field performances of CPV module and single solar cell as the LWPT receivers have been compared. We have found that transmission distance d, divergence half-angle β, rotation angle θ and misalignment distance dmis are most important parameters for multi-field performances and LWPT conversion. The current research provides important references for LWPT system design and optimizations.

A Novel Anti-Offset Interdigital Electrode Capacitive Coupler for Mobile Desktop Charging

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.

High-Misalignment Tolerance Wireless Charging System for Constant Power Output Using Dual Transmission Channels With Magnetic Flux Controlled Inductors

Although the wireless charging system (WCS) achieves flexible power transmission, high system operating performance needs strong anti-misalignment capability and excellent charging controllability. Hence, this article proposes a mistuned WCS that features dual transmission channels using half-bridge inverters, magnetic flux controlled inductors (MFCIs), magnetic couplers with hybrid coils (HMCs), and the series–series compensation. Then, high misalignment tolerance and high-efficient constant power (CP) charging are achieved. First, the interrelation among the mutual inductance, adjustable inductance, load resistance, charging power, and system efficiency is analyzed based on the optimally designed system structure. Second, the circuit structure and working principle of the MFCI are illustrated. Third, the anti-misalignment capability of the optimized HMC is verified by analyzing its coupling characteristics. Then, the relative spatial position between the two HMCs is determined to ensure the negligible cross-coupling influence. In addition, the closed-loop controller's working principle and design method is analyzed to achieve high-efficient and high-controllable CP charging within a wide range of misalignment distance and load resistance. Finally, the experimental results validate the feasibility of the proposed WCS. For CP charging of 150 W, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction misalignment ranges reach ±95% and ±47%, and system efficiency exceeds 90%, superior to the commonly used anti-misalignment methods.

Noncoaxial RDE of circular asymmetry optical vortex for rotating axis detection

We reveal the mechanism of the noncoaxial rotational Doppler effect (RDE) of an optical vortex and report its application in discriminating the orientation of the rotating axis of the rotating body. In most cases of the RDE-based measurement, the beam axis must be aligned with the rotating axis of the rotational body to observe a good signal. Once the beam axis is not coaxial with the rotating axis, the RDE frequency shift would change related to the misalignment distance, which can be called the noncoaxial RDE. Here, we take the advantage of the misaligned RDE augment with precise light-field modulation and successfully realize the discrimination of the orientation of the rotating axis relative to the illuminating beam. We clarify the principle of noncoaxial RDE and explain why the incomplete optical vortex (OV) is sensitive to the position of the rotating axis. We switch the OV field into four quadrants synchronized with sampling by the data acquisition system, and conduct Fourier transformation of the signals. Combined with the fitting algorithm, the orientation of the rotating axis can be recognized directly. This method may find applications for the noncontact detection of rotating bodies in both industrial and astronomical scenarios.

Neural Network for Both Metal Object Detection and Coil Misalignment Prediction in Wireless Power Transfer

This study proposes a method for wireless power transfer (WPT) systems to identify the existence of foreign metal objects and simultaneously predict the misalignment distance between the primary and secondary coils. The proposed method is based on a neural network (NN) trained using electromagnetic field simulations. The training data for the NN consist of differential voltages in the detection coils, together with the input voltage of the primary coil. Although the metallic objects and coil misalignment induce confusing voltages, the trained NN exhibits over 90% accuracy for the validation dataset and mean prediction errors of less than 1 mm for the misalignment distance and ground clearance variance.

PENGARUH JARAK MISALIGNMENT DRIVE SHAFT COOLING TOWER TERHADAP TEGANGAN NORMAL DAN TEGANGAN GESER

The purpose of this study was to determine the effect of misalignment distance of Cooling Tower drive shaft on normal stress and shear stress. Tensions that occur on the shaft continuously for a long time cause the shaft to experience fatigue. The greater misalignment distance will not only damage the shaft but can damage other components. For this reason, the misalignment of the cooling tower shaft is very important to study. This study uses a simulation method by first making a design drawing of the cooling tower drive shaft. Determine the material of the shaft and coupling, then perform simulations and analyze the results. The results of the Von Misses test at the highest and lowest voltages did not show a significant difference this was caused by the voltage difference that was not too far away. The shaft bears varying loads, causing stress along the shaft which results in rapid fatigue. These characteristics are associated with increased load and all indicate that misalignment reduces the life and reliability of the motor and its components. Based on the results of the Von Misses test and the lowest risk displacement that occurs to the effect of this misalignment is the misalignment distance (md = 1 mm), the higher the md value, the greater the risk that occurs to the cooling tower drive shaft.

0001 Associations Between Circadian Factors and Travel Distance with Performance: A retrospective analysis of 2014-2018 National Basketball Association Data

Abstract Introduction Frequent travel across time zones and travelling long distances interferes with healthy sleep and disrupts the circadian system, often degrading athletic performance. National Basketball Association (NBA) players face a demanding travel schedule often requiring multiple games per week, with games spanning the continental United States. This investigation aimed to clarify the influence of circadian factors and travel distance on NBA performance using a dataset from the 2014-2018 seasons. Methods NBA (2014-2018) game data were acquired from an open-access source: (https://www.kaggle.com/ionaskel/nba-games-stats-from-2014-to-2018). Circadian variables of time zone change (TZ∆) and adjusted jet lag (AJL) were formulated, with quadratic versions utilized across analyses. TZ∆ captured circadian delay/advance based on travel for a game, with each TZ going eastward and westward reflected by -1 and +1, respectively. AJL advances TZ∆ by allowing acclimation to a novel TZ, with each day resulting in a 1-unit change towards circadian neutral. AJL is a season-long rolling summation, which was computed using two different travel approaches: Approach1 (AJL1) assumes travel the day before each game, whereas Approach2 (AJL2) was designed to prioritize being home. A standardized flight tracker determined travel distance for each game (GameDistance). Team ability differences, characterized as difference in season win percentages (SeasonWinPerDiff), served as an analytic covariate. Game point differential (PointDiff), defined as a team’s score minus their opponent’s score, and a team’s free throw percentage (FreeThrowPer) served as outcome variables. Linear mixed-effects modeling assessed univariate and multivariate associations, with games nested within both team and year. Results AJL2 (β = -0.63; p = .01) and GameDistance (β = -0.73; p&amp;lt;0.0001) significantly associated with PointDiff. TZ∆ (β = -0.002; p = .03), AJL1 (β = -0.002; p =.04) and GameDistance (β = -0.003; p = 0.007) significantly associated with FreeThrowPer. AJL2 and GameDistance maintained significant relationship with PointDiff in fully adjusted model that included AJL2, GameDistance, and SeasonWinPerDiff. Conclusion Results suggest that both circadian delay/advance and greater distance traveled for games negatively influence NBA performance, even when controlling for differences in team ability. Season travel and flight plans could be constructed to reduce the effects of circadian misalignment and travel distance. Support (If Any) None

Effects of Sleep Restriction on Self-Reported Putting Performance in Golf.

In the present study, we aimed to explore the effects of sleep restriction (SR) on self-reported golf putting skills. Eleven collegiate golfers participated in a self-reported, counterbalanced experimental study under two conditions: (a) a SR condition in which sleep on the night prior to putting was restricted to 4-5 hours, and (b) a habitual normal sleep (NS) condition on the night before the putting test. Following each sleep condition, participants engaged in ten consecutive putting tests at 7 am, 11 am, and 3 pm. Participants reported their subjective sleepiness before each time frame, and their chronotype, defined as their individual circadian preference, was scored based on a morningness-eveningness questionnaire (MEQ). Participants restricted sleep to an average period of 267.6 minutes/night (SD = 51.2) in the SR condition and 426.2 (SD =38.0) minutes/night in the NS condition. A two-way analysis of variance revealed a significant main effect of the sleep condition on the lateral displacement of putts from the target (lateral misalignment) (p = 0.002). In addition, there was a significant main effect of time on distance from the target (distance misalignment) (p = 0.017), indicating less accuracy of putting in the SR condition. In the SR condition, the MEQ score was positively correlated with distance misalignment at 3 pm (ρ = 0.650, p = 0.030), suggesting that morningness types are susceptible to the effects of SR on putting performance. Our findings suggest that golfers should obtain sufficient sleep to optimize putting performance.

High-Misalignment-Tolerant IPT Systems With Solenoid and Double D Pads

The capability of misalignment tolerance is vital for an inductive power transfer (IPT) system. In this article, a new loosely coupled transformer (LCT) structure with series solenoid and DD pads (SDDP) is proposed to improve the misalignment tolerance of the IPT system. The designed LCT not only has strong misalignment-tolerant capability in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -direction but also has strong misalignment-tolerant capability in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> -direction. The fluctuation of mutual inductance is 3.15% within 67.0% misalignment distance of the largest size of the SDDP in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -direction and 44% misalignment distance of the largest size of the SDDP in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> -direction. Finally, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> /S compensated IPT system with 300 W power is built as an example to demonstrate the performance of the proposed LCT. The output voltage fluctuates with the rated load, which is less than 3.2%, and the efficiency is 90.2–91.3%.

The Influence of Local Tapes Misalignment in Stacked YBCO Cable on Its AC Loss

When calculating the AC loss of REBa2Cu3O7−x (REBCO, RE = rare earth) coated conductor cable with stacked geometry, it is often considered that the tapes in the cable is perfectly stacked (there is no transverse misalignment of the tapes). However, the actual stacked cable will have transverse misalignment. The influence of transverse misalignment of tapes on the AC loss of the whole cable needs to be studied in order to understand the actual situation. In this paper, the 2-D H formulation calculated the AC loss of the cable with 10 tapes stacked in three cases. In the first case, the cables are perfectly stacked without lateral misalignment between the tapes. In the second case, the tapes of the cable are oblique to one side. In the third case, the tapes are disordered with each other. The result shows that under the transport current at 50 Hz, when the transport current is less than 0.75Ic0, the transport loss of the cable with obliquely stacked cable is more than the perfectly stacked cable, and when the transport current is greater than 0.75Ic0, the transport loss of the perfectly stacked cable is slightly larger than the obliquely stacked cable. Moreover, the transport loss of disorderly stacked cable is more than perfectly stacked cable at 50 Hz. When the transport current amplitude and the misalignment distance between the tapes in the cable are constant, the transport loss of obliquely stacked cable and disorderly stacked cable relative to perfectly stacked cable both increases first and then decreases as the frequency increases. Under the 50 Hz magnetization field, the magnetization loss of the perfectly stacked cable is less than the cables with oblique misalignment and disorder misalignment. When the amplitude of the external magnetic field and the misalignment distance between the tapes in the cable are constant, the magnetization loss of obliquely stacked cable and disorderly stacked cable relative to perfectly stacked cable also increased first and then decreased as the frequency increased.

ValveTech: A Novel Robotic Approach for Minimally Invasive Aortic Valve Replacement.

Aortic valve disease is the most common heart disease in the elderly calling for replacement with an artificial valve. The presented surgical robot aims to provide a highly controllable instrument for efficient delivery of an artificial valve by the help of integrated endoscopic vision. A robot (called ValveTech), intended for minimally invasive surgery (MIS) and consisting of a flexible cable driven manipulator, a passive arm, and a control unit has been designed and prototyped. The flexible manipulator has several features (e.g., stabilizing flaps, tiny cameras, dexterous introducer and custom cartridge) to help the proper valve placement. It provides 5 degrees of freedom for reaching the operative site via mini-thoracotomy; it adjusts the valve and expands it at the optimal position. The robot was evaluated by ten cardiac surgeons following a real surgical scenario in artificial chest simulator with an aortic mockup. Moreover, after each delivery, the expanded valve was evaluated objectively in comparison with the ideal position. The robot performances were evaluated positively by surgeons. The trials resulted in faster delivery and an average misalignment distance of 3.8 mm along the aorta axis; 16.3 degrees rotational angle around aorta axis and 8.8 degrees misalignment of the valve commissure plane to the ideal plane were measured. The trials successfully proved the proposed system for valve delivery under endoscopic vision. The ValveTech robot can be an alternative solution for minimally invasive aortic valve surgery and improve the quality of the operation both for surgeons and patients.

A Two-Dimensional Mathematical Model to Simulate the Effects of Knee Center Misalignment in Lower-Limb Orthoses

ABSTRACT Introduction Pistoning is relative sliding motion between an affected limb and its corresponding externally fit assistive device (like an orthosis). Pistoning causes skin problems, pain, and discomfort to the orthosis user. Misalignment of an orthotic joint with respect to the anatomical joint is one of the causes of pistoning motion, and the current knowledge pertaining to the effects of orthotic knee center (OKC) misalignments in lower-limb orthoses is limited. This work quantifies the effects of OKC misalignment in terms of relative motion between the limb and the orthosis and predicts locations of resultant pressure point on the limb. Method A two-dimensional link segment model that simulates relative motion between the limb and orthosis was developed. The OKC was systematically misaligned in the anterior-posterior (A-P), proximal-distal (P-D) directions, and their combination to simulate orthosis/thigh strap sliding and identify pressure points on the thigh. Simulations were performed for stand-to-sit activity and walking with a knee-ankle-foot orthosis. Results It was found that OKC misalignment causes increased A-P and P-D relative motions with an increase in misalignment distance for the stand-to-sit activity. The A-P and P-D relative motions are of greater concern for activities involving increased knee flexion such as sitting, squatting, and kneeling as compared with walking with an orthosis. Although the A-P and P-D relative motions during walking are of small magnitude, they occur with reversals in the direction and are repetitive in nature, which may cause skin problems and discomfort due to recurring pressure points. Conclusions The model provides a means to study the consequences of misalignment and insights for orthosis modification for improved comfort. A software simulation tool based on the presented model can serve as an educational and training tool in prosthetics and orthotics courses for creating awareness about the importance of proper alignment of orthotic knee joints. Study of misalignments of this nature will also guide fabrication and fitting of lower-limb orthoses/exoskeletons.

상용 드론의 고전력 무선충전을 위한 광역 스테이션

This study investigates high-power wireless power transfer(WPT) with a wide charging area for large drones. The overall size of the receiving coil(Rx-coil) connected to the leg of the drone on the bottom side is 420×420×10 mm. Transmitting coils(Tx-coils) of three different shapes are individually optimized and combined to achieve a uniform magnetic field intensity and high power transfer efficiency(PTE) retention rate. The overall dimension of %the Tx-coil including the case thickness is 1,000×1,000×105 mm. The quality factors of the optimized Tx- and Rx-coils are 120 and 54, respectively, expressing a high PTE according to the transmission and misalignment distances. Based on the center between the coils, the PTE is 91 % and 80 % at a transmission distance of 50 mm and 300 mm, respectively. The PTE is 89.5 % when the Rx-coils are positioned at a misalignment distance of 285 mm, which indicates the edge of the Tx-coil in the charging area. The coils are connected to various equipment(e.g., signal source, Tx- and Rx-modules, load, etc.) to verify the WPT system. The system efficiency considering loss is 69 % because the input and output powers are 174.7 W and 120.3 W, respectively. In addition, an electromagnetic wave is measured below the electromagnetic interference standard.

Estimating refractive index structure constant and extinction coefficient under misalignment

This paper presents two methods, named the irradiance fitting method and the irradiance integration method, for the estimation of refractive index structure constant (Cn2) and extinction coefficient under misalignment. Validations of the methods are carried out based on experimentally obtained speckle images. These two methods are feasible and accurate regardless of whether the optical axis misalignment distance is calibrated, which provides an effective and convenient approach for free space optical communication (FSOC) atmospheric channel research.

A Hybrid Inductive Power Transfer System With Misalignment Tolerance Using Quadruple-D Quadrature Pads

Pad misalignments are almost inevitable in most inductive power transfer (IPT) systems. It tends to cause parameter variations and, thus, significantly affects the performance of the IPT system. In this article, a hybrid IPT system with misalignment tolerance using the quadruple-D quadrature pads (QDQPs) is proposed to tolerate the x, y, z, and diagonal misalignments with load-independent output voltage, simplifying or even canceling control schemes. Besides, the proposed approach can restrict the increase of the primary current when the secondary side moves out of the operating region. Moreover, a new parametric design method is presented according to the misalignment characteristics of QDQPs. The method can limit the output voltage fluctuation to a certain range, given a predetermined misalignment distance. A 3.5-kW prototype was built to verify the proposed hybrid IPT system. The primary and secondary coil sizes are 400 mm × 400 mm, and the air gap is 150 mm. Experimental results demonstrate that the proposed hybrid system can tolerate -150 to +150 mm x-misalignment, -150 to +150 mm y-misalignment, -20 to +35 mm z-misalignment, and -100 to +100 mm diagonal misalignment with load-independent output voltage. Within the predetermined misalignment range, the output voltage fluctuation is less than 5%.