Planar and ultrathin liquid crystal(LC)polarization optical elements have found promising applications in augmented reality(AR),virtual reality(VR),and photonic devices.In this paper,we give a comprehensive review on ...Planar and ultrathin liquid crystal(LC)polarization optical elements have found promising applications in augmented reality(AR),virtual reality(VR),and photonic devices.In this paper,we give a comprehensive review on the operation principles,device fabrication,and performance of these optical elements.Optical simulations methods for optimizing the device performance are discussed in detail.Finally,some potential applications of these devices in AR and VR systems are illustrated and analyzed.展开更多
Mixed reality(MR)technology is a new digital holographic image technology,which appears in the field of graphics after virtual reality(VR)and augmented reality(AR)technology,a new interdisciplinary frontier.As a new g...Mixed reality(MR)technology is a new digital holographic image technology,which appears in the field of graphics after virtual reality(VR)and augmented reality(AR)technology,a new interdisciplinary frontier.As a new generation of technology,MR has attracted great attention of clinicians in recent years.The emergence of MR will bring about revolutionary changes in medical education training,medical research,medical communication,and clinical treatment.At present,MR technology has become the popular frontline information technology for medical applications.With the popularization of digital technology in the medical field,the development prospects of MR are inestimable.The purpose of this review article is to introduce the application of MR technology in the medical field and prospect its trend in the future.展开更多
It is a comparatively convenient technique to investigate the motion of a particle with the help of the differential geometry the-ory,rather than directly decomposing the motion in the Cartesian coordinates.The new mo...It is a comparatively convenient technique to investigate the motion of a particle with the help of the differential geometry the-ory,rather than directly decomposing the motion in the Cartesian coordinates.The new model of three-dimensional (3D) guidance problem for interceptors is presented in this paper,based on the classical differential geometry curve theory.Firstly,the kinematical equations of the line of sight (LOS) are gained by carefully investigating the rotation principle of LOS,the kinematic equations of LOS are established,and the concepts of curvature and torsion of LOS are proposed.Simultaneously,the new relative dynamic equations between interceptor and target are constructed.Secondly,it is found that there is an instan-taneous rotation plane of LOS (IRPL) in the space,in which two-dimensional (2D) guidance laws could be constructed to solve 3D interception guidance problems.The spatial 3D true proportional navigation (TPN) guidance law could be directly introduced in IRPL without approximation and linearization for dimension-reduced 2D TPN.In addition,the new series of augmented TPN (APN) and LOS angular acceleration guidance laws (AAG) could also be gained in IRPL.After that,the dif-ferential geometric guidance commands (DGGC) of guidance laws in IRPL are advanced,and we prove that the guidance commands in arc-length system proposed by Chiou and Kuo are just a special case of DGGC.Moreover,the performance of the original guidance laws will be reduced after the differential geometric transformation.At last,an exoatmospheric intercep-tion is taken for simulation to demonstrate the differential geometric modeling proposed in this paper.展开更多
Background: Augmented reality(AR) technology is used to reconstruct three-dimensional(3D) images of hepatic and biliary structures from computed tomography and magnetic resonance imaging data, and to superimpose the v...Background: Augmented reality(AR) technology is used to reconstruct three-dimensional(3D) images of hepatic and biliary structures from computed tomography and magnetic resonance imaging data, and to superimpose the virtual images onto a view of the surgical field. In liver surgery, these superimposed virtual images help the surgeon to visualize intrahepatic structures and therefore, to operate precisely and to improve clinical outcomes.Data Sources: The keywords "augmented reality", "liver", "laparoscopic" and "hepatectomy" were used for searching publications in the Pub Med database. The primary source of literatures was from peer-reviewed journals up to December 2016. Additional articles were identified by manual search of references found in the key articles.Results: In general, AR technology mainly includes 3D reconstruction, display, registration as well as tracking techniques and has recently been adopted gradually for liver surgeries including laparoscopy and laparotomy with video-based AR assisted laparoscopic resection as the main technical application. By applying AR technology, blood vessels and tumor structures in the liver can be displayed during surgery,which permits precise navigation during complex surgical procedures. Liver transformation and registration errors during surgery were the main factors that limit the application of AR technology.Conclusions: With recent advances, AR technologies have the potential to improve hepatobiliary surgical procedures. However, additional clinical studies will be required to evaluate AR as a tool for reducing postoperative morbidity and mortality and for the improvement of long-term clinical outcomes. Future research is needed in the fusion of multiple imaging modalities, improving biomechanical liver modeling,and enhancing image data processing and tracking technologies to increase the accuracy of current AR methods.展开更多
In the past two decades, augmented reality （AR） has received a growing amount of attention by researchers in the manufacturing technology community, because AR can be applied to address a wide range of problems thro...In the past two decades, augmented reality （AR） has received a growing amount of attention by researchers in the manufacturing technology community, because AR can be applied to address a wide range of problems throughout the assembly phase in the lifecycle of a product, e.g., planning, design, ergonomics assessment, operation guidance and training. However, to the best of authors＇ knowledge, there has not been any comprehensive review of AR-based assembly systems. This paper aims to provide a concise overview of the technical features, characteristics and broad range of applications of AR- based assembly systems published between 1990 and 2015. Among these selected articles, two thirds of them were published between 2005 and 2015, and they are considered as recent pertinent works which will be discussed in detail. In addition, the current limitation factors and future trends in the development will also be discussed.展开更多
The unscented Kalman filter(UKF) has four implementations in the additive noise case,according to whether the state is augmented with noise vectors and whether a new set of sigma points is redrawn from the predicted s...The unscented Kalman filter(UKF) has four implementations in the additive noise case,according to whether the state is augmented with noise vectors and whether a new set of sigma points is redrawn from the predicted state(which is so-called resampling) for the observation prediction.This paper concerns the differences of performances for those implementations,such as accuracy,adaptability,computational complexity,etc.The conditionally equivalent relationships between the augmented and non-augmented unscented transforms(UTs) are proved for several sampling strategies that are commonly used.Then,we find that the augmented and non-augmented UKFs have the same filter results with the additive measurement noise,but only have the same state predictions with the additive process noise.Resampling is not believed to be necessary in some researches.However,we find out that resampling can be helpful for an adaptive Kalman gain.This will improve the convergence and accuracy of the filter when the large scale state modeling bias or unknown maneuvers occur.Finally,some universal designing principles for a practical UKF are given as follows:1) for the additive observation noise case,it's better to use the non-augmented UKF;2) for the additive process noise case,when the small state modeling bias or maneuvers are involved,the non-resampling algorithms with state whether augmented or not are candidates for filters;3) the resampling and non-augmented algorithm is the only choice while the large state modeling bias or maneuvers are latent.展开更多
Near-eye displays are the main platform devices for many augmented reality(AR)and virtual reality(VR)applications.As a wearable device,a near-eye display should have a compact form factor and be lightweight.Furthermor...Near-eye displays are the main platform devices for many augmented reality(AR)and virtual reality(VR)applications.As a wearable device,a near-eye display should have a compact form factor and be lightweight.Furthermore,a large field of view and sufficient eyebox are crucial for immersive viewing conditions.Natural three-dimensional(3D)image presentation with proper focus cues is another requirement that enables a comfortable viewing experience and natural user interaction.Finally,in the case of AR,the device should allow for an optical see-through view of the real world.Conventional bulk optics and two-dimensional display panels exhibit clear limitations when implementing these requirements.Holographic techniques have been applied to near-eye displays in various aspects to overcome the limitations of conventional optics.The wavefront reconstruction capability of holographic techniques has been extensively exploited to develop optical see-through 3D holographic near-eye displays of glass-like form factors.In this article,the application of holographic techniques to AR and VR near-eye displays is reviewed.Various applications are introduced,such as static holographic optical components and dynamic holographic display devices.Current issues and recent progress are also reviewed,providing a comprehensive overview of holographic techniques that are applied to AR and VR near-eye displays.展开更多
To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. T...To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. Three-dimensional surface models of the jawbones, based on the computed tomography data, were used to create the integral videography images of a subject＇s maxillofacial area. The three-dimensional augmented reality system （integral videography display, computed tomography, a position tracker and a computer） was used to generate a three-dimensional overlay that was projected on the surgical site via a half-silvered mirror. Thereafter, a feasibility study was performed on a volunteer. The accuracy of this system was verified on a solid model while simulating bone resection. Positional registration was attained by identifying and tracking the patient/surgical instrument＇s position. Thus, integral videography images of jawbones, teeth and the surgical tool were superimposed in the correct position. Stereoscopic images viewed from various angles were accurately displayed. Change in the viewing angle did not negatively affect the surgeon＇s ability to simultaneously observe the three-dimensional images and the patient, without special glasses. The difference in three-dimensional position of each measuring point on the solid model and augmented reality navigation was almost negligible （〈1 mm）; this indicates that the system was highly accurate. This augmented reality system was highly accurate and effective for surgical navigation and for overlaying a three-dimensional computed tomography image on a patient＇s surgical area, enabling the surgeon to understand the positional relationship between the preoperative image and the actual surgical site, with the naked eye.展开更多
Mitigation of sonic boom to an acceptable stage is a key point for the next generation of supersonic transports. Meanwhile, designing a supersonic aircraft with an ideal ground signature is always the focus of researc...Mitigation of sonic boom to an acceptable stage is a key point for the next generation of supersonic transports. Meanwhile, designing a supersonic aircraft with an ideal ground signature is always the focus of research on sonic boom reduction. This paper presents an inverse design approach to optimize the near-field signature of an aircraft, making it close to the shaped ideal ground signature after the propagation in the atmosphere. Using the Proper Orthogonal Decomposition(POD) method, a guessed input of augmented Burgers equation is inversely achieved. By multiple POD iterations, the guessed ground signatures successively approach the target ground signature until the convergence criteria is reached. Finally, the corresponding equivalent area distribution is calculated from the optimal near-field signature through the classical Whitham F-function theory. To validate this method, an optimization example of Lockheed Martin 1021 is demonstrated. The modified configuration has a fully shaped ground signature and achieves a drop of perceived loudness by 7.94 PLdB. This improvement is achieved via shaping the original near-field signature into wiggles and damping it by atmospheric attenuation. At last, a nonphysical ground signature is set as the target to test the robustness of this inverse design method and shows that this method is robust enough for various inputs.展开更多
The popularity of wearable devices and smartphones has fueled the development of Mobile Augmented Reality(MAR),which provides immersive experiences over the real world using techniques,such as computer vision and deep...The popularity of wearable devices and smartphones has fueled the development of Mobile Augmented Reality(MAR),which provides immersive experiences over the real world using techniques,such as computer vision and deep learning.However,the hardware-specific MAR is costly and heavy,and the App-based MAR requires an additional download and installation and it also lacks cross-platform ability.These limitations hamper the pervasive promotion of MAR.This paper argues that mobile Web AR(MWAR)holds the potential to become a practical and pervasive solution that can effectively scale to millions of end-users because MWAR can be developed as a lightweight,cross-platform,and low-cost solution for end-to-end delivery of MAR.The main challenges for making MWAR a reality lie in the low efficiency for dense computing in Web browsers,a large delay for real-time interactions over mobile networks,and the lack of standardization.The good news is that the newly emerging 5G and Beyond 5G(B5G)cellular networks can mitigate these issues to some extent via techniques such as network slicing,device-to-device communication,and mobile edge computing.In this paper,we first give an overview of the challenges and opportunities of MWAR in the 5G era.Then we describe our design and development of a generic service-oriented framework(called MWAR5)to provide a scalable,flexible,and easy to deploy MWAR solution.We evaluate the performance of our MWAR5 system in an actually deployed 5G trial network under the collaborative configurations,which shows encouraging results.Moreover,we also share the experiences and insights from our development and deployment,including some exciting future directions of MWAR over 5G and B5G networks.展开更多
Augmented reality(AR)display,which superimposes virtual images on ambient scene,can visually blend the physical world and the digital world and thus opens a new vista for human–machine interaction.AR display is consi...Augmented reality(AR)display,which superimposes virtual images on ambient scene,can visually blend the physical world and the digital world and thus opens a new vista for human–machine interaction.AR display is considered as one of the next-generation display technologies and has been drawing huge attention from both academia and industry.Current AR display systems operate based on a combination of various refractive,reflective,and diffractive optical elements,such as lenses,prisms,mirrors,and gratings.Constrained by the underlying physical mechanisms,these conventional elements only provide limited light-field modulation capability and suffer from issues such as bulky volume and considerable dispersion,resulting in large size,severe chromatic aberration,and narrow field of view of the composed AR display system.Recent years have witnessed the emerging of a new type of optical elements—metasurfaces,which are planar arrays of subwavelength electromagnetic structures that feature an ultracompact footprint and flexible light-field modulation capability,and are widely believed to be an enabling tool for overcoming the limitations faced by current AR displays.Here,we aim to provide a comprehensive review on the recent development of metasurface-enabled AR display technology.We first familiarize readers with the fundamentals of AR display,covering its basic working principle,existing conventional-optics-based solutions,as well as the associated pros and cons.We then introduce the concept of optical metasurfaces,emphasizing typical operating mechanisms,and representative phase modulation methods.We elaborate on three kinds of metasurface devices,namely,metalenses,metacouplers,and metaholograms,which have empowered different forms of AR displays.Their physical principles,device designs,and the performance improvement of the associated AR displays are explained in details.In the end,we discuss the existing challenges of metasurface optics for AR display applications and provide our perspective on future research endea展开更多
In this paper, a new nonlinear augmented observer is proposed and applied to satellite attitude control systems. The observer can estimate system state and actuator fault simultaneously. It can enhance the performance...In this paper, a new nonlinear augmented observer is proposed and applied to satellite attitude control systems. The observer can estimate system state and actuator fault simultaneously. It can enhance the performances of rapidly-varying faults estimation. Only original system matrices are adopted in the parameter design. The considered faults can be unbounded, and the proposed augmented observer can estimate a large class of faults. Systems without disturbances and the fault whose finite times derivatives are zero piecewise are initially considered, followed by a discussion of a general situation where the system is subject to disturbances and the finite times derivatives of the faults are not null but bounded. For the considered nonlinear system, convergence conditions of the observer are provided and the stability analysis is performed using Lyapunov direct method. Then a feasible algorithm is explored to compute the observer parameters using linear matrix inequalities （LMIs）. Finally, the effectiveness of the proposed approach is illustrated by considering an example of a closed-loop satellite attitude control system. The mance in estimating states and actuator faults. It also successfully. simulation results show satisfactory perfor- shows that multiple faults can be estimated展开更多
This paper presents an augmented network model to represent urban transit system.Through such network model,the urban transit assignment problem can be easily modeled like a generalized traffic network.Simultaneously,...This paper presents an augmented network model to represent urban transit system.Through such network model,the urban transit assignment problem can be easily modeled like a generalized traffic network.Simultaneously,the feasible route in such augmented transit network is then defined in accordance with the passengers＇ behaviors.The passengers＇ travel costs including walking time,waiting time,in-vehicle time and transfer time are formulated while the congestions at stations and the congestions in transit vehicles are all taken into account.On the base of these,an equilibrium model for urban transit assignment problem is presented and an improved shortest path method based algorithm is also proposed to solve it.Finally,a numerical example is provided to illustrate our approach.展开更多
Augmented reality(AR)displays are attracting significant attention and efforts.In this paper,we review the adopted device configurations of see-through displays,summarize the current development status and highlight f...Augmented reality(AR)displays are attracting significant attention and efforts.In this paper,we review the adopted device configurations of see-through displays,summarize the current development status and highlight future challenges in micro-displays.A brief introduction to optical gratings is presented to help understand the challenging design of grating-based waveguide for AR displays.Finally,we discuss the most recent progress in diffraction grating and its implications.展开更多
Background:In recent years,the development of digital imaging technology has had a significant influence in liver surgery.The ability to obtain a 3-dimensional(3D)visualization of the liver anatomy has provided surger...Background:In recent years,the development of digital imaging technology has had a significant influence in liver surgery.The ability to obtain a 3-dimensional(3D)visualization of the liver anatomy has provided surgery with virtual reality of simulation 3D computer models,3D printing models and more recently holograms and augmented reality(when virtual reality knowledge is superimposed onto reality).In addition,the utilization of real-time fluorescent imaging techniques based on indocyanine green(ICG)uptake allows clinicians to precisely delineate the liver anatomy and/or tumors within the parenchyma,applying the knowledge obtained preoperatively through digital imaging.The combination of both has transformed the abstract thinking until now based on 2D imaging into a 3D preoperative conception(virtual reality),enhanced with real-time visualization of the fluorescent liver structures,effectively facilitating intraoperative navigated liver surgery(augmented reality).Data sources:A literature search was performed from inception until January 2021 in MEDLINE(Pub Med),Embase,Cochrane library and database for systematic reviews(CDSR),Google Scholar,and National Institute for Health and Clinical Excellence(NICE)databases.Results:Fifty-one pertinent articles were retrieved and included.The different types of digital imaging technologies and the real-time navigated liver surgery were estimated and compared.Conclusions:ICG fluorescent imaging techniques can contribute essentially to the real-time definition of liver segments;as a result,precise hepatic resection can be guided by the presence of fluorescence.Furthermore,3D models can help essentially to further advancing of precision in hepatic surgery by permitting estimation of liver volume and functional liver remnant,delineation of resection lines along the liver segments and evaluation of tumor margins.In liver transplantation and especially in living donor liver transplantation(LDLT),3D printed models of the donor’s liver and models of the recipient’s hilar anatom展开更多
Intuitive and efficient interfaces for human- robot interaction （HRI） have been a challenging issue in robotics as it is essential for the prevalence of robots supporting humans in key areas of activities. This pape...Intuitive and efficient interfaces for human- robot interaction （HRI） have been a challenging issue in robotics as it is essential for the prevalence of robots supporting humans in key areas of activities. This paper presents a novel augmented reality （AR） based interface to facilitate human-virtual robot interaction. A number of human-virtual robot interaction methods have been for- mulated and implemented with respect to the various types of operations needed in different robotic applications. A Euclidean distance-based method is developed to assist the users in the interaction with the virtual robot and the spatial entities in an AR environment. A monitor-based visualization mode is adopted as it enables the users to perceive the virtual contents associated with different interaction methods, and the virtual content augmented in the real environment is informative and useful to the users during their interaction with the virtual robot. Case researches are presented to demonstrate the successful implementation of the AR-based HRI interface in planning robot pick-and-place operations and path following operations.展开更多
Power augmented ram （PAR）engine is a popular equipment to reduce the requirement of power for takeoff and improve aerodynamic performance. To provide detailed insight into the aerodynamic characteristics of wing-in-...Power augmented ram （PAR）engine is a popular equipment to reduce the requirement of power for takeoff and improve aerodynamic performance. To provide detailed insight into the aerodynamic characteristics of wing-in-ground effect （WIG）craft with PAR engine, numerical simulations are carried out on WIG craft models in cruise. Simplified engine models are applied to the simulations. Two cruise modes for PAR engine are considered. The aerodynamic characteristics of the WIG craft and other features are studied. Comparisons with WIG craft model without PAR show that shutoff of PAR engine results in an increase in drag and less change in lift. Accordingly for the work of PAR engine, the air flow blown from the engine accelerates the flow around the upper surface and a high-speed attached flow near the trailing edge is recorded. With the schemed PAR flow, more suction force is realized and the flow features over the wing vary noticeably. It is also shown that the Coanda effect,provided with an attached flow, introduces an appropriate and practical flow mode for WIG craft with PAR engine in cruise. The results refresh our understanding on aerodynamic characteristics of WIG craft.展开更多
Flood visualization is an effective and intuitive tool for representing flood information from abstract spatiotemporal data.With the growing demand for flood disaster visualizations and mitigation,augmented flood visu...Flood visualization is an effective and intuitive tool for representing flood information from abstract spatiotemporal data.With the growing demand for flood disaster visualizations and mitigation,augmented flood visualizations that support decision makers’perspectives are needed,which can be enhanced by emerging augmented reality(AR)and 3D printing technologies.This paper proposes an innovative flood AR visualization method based on a 3D-printed terrain model and investigates essential techniques,such as the suitable size calculation of the terrain models,the adaptive processing of flood data,and hybridizing virtual flood and terrain models.A prototype experimental system(PES)based on the proposed method and a comparison experimental system(CES)based on a virtual terrain are developed to conduct comparative experiments,which combine the system performance and questionnaire method to evaluate the efficiency and usability of the proposed method.The statistical results indicate that the method is useful for assisting participants in understanding the flood hazard and providing a more intuitive and realistic visual experience compared with that of the traditional AR flood visualization method.The frame rate is stable at 60 frames per second(FPS),which means that the proposed method is more efficient than the traditional AR flood visualization method.展开更多
文摘Planar and ultrathin liquid crystal(LC)polarization optical elements have found promising applications in augmented reality(AR),virtual reality(VR),and photonic devices.In this paper,we give a comprehensive review on the operation principles,device fabrication,and performance of these optical elements.Optical simulations methods for optimizing the device performance are discussed in detail.Finally,some potential applications of these devices in AR and VR systems are illustrated and analyzed.
文摘Mixed reality(MR)technology is a new digital holographic image technology,which appears in the field of graphics after virtual reality(VR)and augmented reality(AR)technology,a new interdisciplinary frontier.As a new generation of technology,MR has attracted great attention of clinicians in recent years.The emergence of MR will bring about revolutionary changes in medical education training,medical research,medical communication,and clinical treatment.At present,MR technology has become the popular frontline information technology for medical applications.With the popularization of digital technology in the medical field,the development prospects of MR are inestimable.The purpose of this review article is to introduce the application of MR technology in the medical field and prospect its trend in the future.
文摘It is a comparatively convenient technique to investigate the motion of a particle with the help of the differential geometry the-ory,rather than directly decomposing the motion in the Cartesian coordinates.The new model of three-dimensional (3D) guidance problem for interceptors is presented in this paper,based on the classical differential geometry curve theory.Firstly,the kinematical equations of the line of sight (LOS) are gained by carefully investigating the rotation principle of LOS,the kinematic equations of LOS are established,and the concepts of curvature and torsion of LOS are proposed.Simultaneously,the new relative dynamic equations between interceptor and target are constructed.Secondly,it is found that there is an instan-taneous rotation plane of LOS (IRPL) in the space,in which two-dimensional (2D) guidance laws could be constructed to solve 3D interception guidance problems.The spatial 3D true proportional navigation (TPN) guidance law could be directly introduced in IRPL without approximation and linearization for dimension-reduced 2D TPN.In addition,the new series of augmented TPN (APN) and LOS angular acceleration guidance laws (AAG) could also be gained in IRPL.After that,the dif-ferential geometric guidance commands (DGGC) of guidance laws in IRPL are advanced,and we prove that the guidance commands in arc-length system proposed by Chiou and Kuo are just a special case of DGGC.Moreover,the performance of the original guidance laws will be reduced after the differential geometric transformation.At last,an exoatmospheric intercep-tion is taken for simulation to demonstrate the differential geometric modeling proposed in this paper.
基金supported by grants from the Mission Plan Program of Beijing Municipal Administration of Hospitals(SML20152201)Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding(ZYLX201712)+1 种基金the National Natural Science Foundation of China(81427803)Beijing Tsinghua Changgung Hospital Fund(12015C1039)
文摘Background: Augmented reality(AR) technology is used to reconstruct three-dimensional(3D) images of hepatic and biliary structures from computed tomography and magnetic resonance imaging data, and to superimpose the virtual images onto a view of the surgical field. In liver surgery, these superimposed virtual images help the surgeon to visualize intrahepatic structures and therefore, to operate precisely and to improve clinical outcomes.Data Sources: The keywords "augmented reality", "liver", "laparoscopic" and "hepatectomy" were used for searching publications in the Pub Med database. The primary source of literatures was from peer-reviewed journals up to December 2016. Additional articles were identified by manual search of references found in the key articles.Results: In general, AR technology mainly includes 3D reconstruction, display, registration as well as tracking techniques and has recently been adopted gradually for liver surgeries including laparoscopy and laparotomy with video-based AR assisted laparoscopic resection as the main technical application. By applying AR technology, blood vessels and tumor structures in the liver can be displayed during surgery,which permits precise navigation during complex surgical procedures. Liver transformation and registration errors during surgery were the main factors that limit the application of AR technology.Conclusions: With recent advances, AR technologies have the potential to improve hepatobiliary surgical procedures. However, additional clinical studies will be required to evaluate AR as a tool for reducing postoperative morbidity and mortality and for the improvement of long-term clinical outcomes. Future research is needed in the fusion of multiple imaging modalities, improving biomechanical liver modeling,and enhancing image data processing and tracking technologies to increase the accuracy of current AR methods.
文摘In the past two decades, augmented reality （AR） has received a growing amount of attention by researchers in the manufacturing technology community, because AR can be applied to address a wide range of problems throughout the assembly phase in the lifecycle of a product, e.g., planning, design, ergonomics assessment, operation guidance and training. However, to the best of authors＇ knowledge, there has not been any comprehensive review of AR-based assembly systems. This paper aims to provide a concise overview of the technical features, characteristics and broad range of applications of AR- based assembly systems published between 1990 and 2015. Among these selected articles, two thirds of them were published between 2005 and 2015, and they are considered as recent pertinent works which will be discussed in detail. In addition, the current limitation factors and future trends in the development will also be discussed.
基金supported by the National Defense Pre-Research Foundation of China (Grant No 9140A21010908KG0162)CAST Foundation (Grant No 2009-HT-GFKD)
文摘The unscented Kalman filter(UKF) has four implementations in the additive noise case,according to whether the state is augmented with noise vectors and whether a new set of sigma points is redrawn from the predicted state(which is so-called resampling) for the observation prediction.This paper concerns the differences of performances for those implementations,such as accuracy,adaptability,computational complexity,etc.The conditionally equivalent relationships between the augmented and non-augmented unscented transforms(UTs) are proved for several sampling strategies that are commonly used.Then,we find that the augmented and non-augmented UKFs have the same filter results with the additive measurement noise,but only have the same state predictions with the additive process noise.Resampling is not believed to be necessary in some researches.However,we find out that resampling can be helpful for an adaptive Kalman gain.This will improve the convergence and accuracy of the filter when the large scale state modeling bias or unknown maneuvers occur.Finally,some universal designing principles for a practical UKF are given as follows:1) for the additive observation noise case,it's better to use the non-augmented UKF;2) for the additive process noise case,when the small state modeling bias or maneuvers are involved,the non-resampling algorithms with state whether augmented or not are candidates for filters;3) the resampling and non-augmented algorithm is the only choice while the large state modeling bias or maneuvers are latent.
基金National Research Foundation of Korea(NRF-2017R1A2B2011084).
文摘Near-eye displays are the main platform devices for many augmented reality(AR)and virtual reality(VR)applications.As a wearable device,a near-eye display should have a compact form factor and be lightweight.Furthermore,a large field of view and sufficient eyebox are crucial for immersive viewing conditions.Natural three-dimensional(3D)image presentation with proper focus cues is another requirement that enables a comfortable viewing experience and natural user interaction.Finally,in the case of AR,the device should allow for an optical see-through view of the real world.Conventional bulk optics and two-dimensional display panels exhibit clear limitations when implementing these requirements.Holographic techniques have been applied to near-eye displays in various aspects to overcome the limitations of conventional optics.The wavefront reconstruction capability of holographic techniques has been extensively exploited to develop optical see-through 3D holographic near-eye displays of glass-like form factors.In this article,the application of holographic techniques to AR and VR near-eye displays is reviewed.Various applications are introduced,such as static holographic optical components and dynamic holographic display devices.Current issues and recent progress are also reviewed,providing a comprehensive overview of holographic techniques that are applied to AR and VR near-eye displays.
基金supported by a Grant-in-Aid for Scientific Research (22659366) from the Japan Society for the Promotion of Science
文摘To evaluate the feasibility and accuracy of a three-dimensional augmented reality system incorporating integral videography for imaging oral and maxillofacial regions, based on preoperative computed tomography data. Three-dimensional surface models of the jawbones, based on the computed tomography data, were used to create the integral videography images of a subject＇s maxillofacial area. The three-dimensional augmented reality system （integral videography display, computed tomography, a position tracker and a computer） was used to generate a three-dimensional overlay that was projected on the surgical site via a half-silvered mirror. Thereafter, a feasibility study was performed on a volunteer. The accuracy of this system was verified on a solid model while simulating bone resection. Positional registration was attained by identifying and tracking the patient/surgical instrument＇s position. Thus, integral videography images of jawbones, teeth and the surgical tool were superimposed in the correct position. Stereoscopic images viewed from various angles were accurately displayed. Change in the viewing angle did not negatively affect the surgeon＇s ability to simultaneously observe the three-dimensional images and the patient, without special glasses. The difference in three-dimensional position of each measuring point on the solid model and augmented reality navigation was almost negligible （〈1 mm）; this indicates that the system was highly accurate. This augmented reality system was highly accurate and effective for surgical navigation and for overlaying a three-dimensional computed tomography image on a patient＇s surgical area, enabling the surgeon to understand the positional relationship between the preoperative image and the actual surgical site, with the naked eye.
文摘Mitigation of sonic boom to an acceptable stage is a key point for the next generation of supersonic transports. Meanwhile, designing a supersonic aircraft with an ideal ground signature is always the focus of research on sonic boom reduction. This paper presents an inverse design approach to optimize the near-field signature of an aircraft, making it close to the shaped ideal ground signature after the propagation in the atmosphere. Using the Proper Orthogonal Decomposition(POD) method, a guessed input of augmented Burgers equation is inversely achieved. By multiple POD iterations, the guessed ground signatures successively approach the target ground signature until the convergence criteria is reached. Finally, the corresponding equivalent area distribution is calculated from the optimal near-field signature through the classical Whitham F-function theory. To validate this method, an optimization example of Lockheed Martin 1021 is demonstrated. The modified configuration has a fully shaped ground signature and achieves a drop of perceived loudness by 7.94 PLdB. This improvement is achieved via shaping the original near-field signature into wiggles and damping it by atmospheric attenuation. At last, a nonphysical ground signature is set as the target to test the robustness of this inverse design method and shows that this method is robust enough for various inputs.
基金supported in part by the National Key R&D Program of China under Grant 2018YFE0205503in part by the National Natural Science Foundation of China (NSFC) under Grant 61671081+4 种基金in part by the Funds for International Cooperation and Exchange of NSFC under Grant 61720106007in part by the 111 Project under Grant B18008in part by the Beijing Natural Science Foundation under Grant 4172042in part by the Fundamental Research Funds for the Central Universities under Grant 2018XKJC01in part by the BUPT Excellent Ph.D. Students Foundation under Grant CX2019213
文摘The popularity of wearable devices and smartphones has fueled the development of Mobile Augmented Reality(MAR),which provides immersive experiences over the real world using techniques,such as computer vision and deep learning.However,the hardware-specific MAR is costly and heavy,and the App-based MAR requires an additional download and installation and it also lacks cross-platform ability.These limitations hamper the pervasive promotion of MAR.This paper argues that mobile Web AR(MWAR)holds the potential to become a practical and pervasive solution that can effectively scale to millions of end-users because MWAR can be developed as a lightweight,cross-platform,and low-cost solution for end-to-end delivery of MAR.The main challenges for making MWAR a reality lie in the low efficiency for dense computing in Web browsers,a large delay for real-time interactions over mobile networks,and the lack of standardization.The good news is that the newly emerging 5G and Beyond 5G(B5G)cellular networks can mitigate these issues to some extent via techniques such as network slicing,device-to-device communication,and mobile edge computing.In this paper,we first give an overview of the challenges and opportunities of MWAR in the 5G era.Then we describe our design and development of a generic service-oriented framework(called MWAR5)to provide a scalable,flexible,and easy to deploy MWAR solution.We evaluate the performance of our MWAR5 system in an actually deployed 5G trial network under the collaborative configurations,which shows encouraging results.Moreover,we also share the experiences and insights from our development and deployment,including some exciting future directions of MWAR over 5G and B5G networks.
基金would like to acknowl-edge the support of the National Natural Science Foundation of China(NSFC)(Grant Nos.62075078 and 62135004)support of the Knowledge Innovation Program of Wuhan-Shuguang Project(Grant No.2022010801020095).Z.L.would like to acknowledge the support of the NSFC(Grant No.62205113)the China Postdoctoral Science Foundation(Grant No.2022M721244).
文摘Augmented reality(AR)display,which superimposes virtual images on ambient scene,can visually blend the physical world and the digital world and thus opens a new vista for human–machine interaction.AR display is considered as one of the next-generation display technologies and has been drawing huge attention from both academia and industry.Current AR display systems operate based on a combination of various refractive,reflective,and diffractive optical elements,such as lenses,prisms,mirrors,and gratings.Constrained by the underlying physical mechanisms,these conventional elements only provide limited light-field modulation capability and suffer from issues such as bulky volume and considerable dispersion,resulting in large size,severe chromatic aberration,and narrow field of view of the composed AR display system.Recent years have witnessed the emerging of a new type of optical elements—metasurfaces,which are planar arrays of subwavelength electromagnetic structures that feature an ultracompact footprint and flexible light-field modulation capability,and are widely believed to be an enabling tool for overcoming the limitations faced by current AR displays.Here,we aim to provide a comprehensive review on the recent development of metasurface-enabled AR display technology.We first familiarize readers with the fundamentals of AR display,covering its basic working principle,existing conventional-optics-based solutions,as well as the associated pros and cons.We then introduce the concept of optical metasurfaces,emphasizing typical operating mechanisms,and representative phase modulation methods.We elaborate on three kinds of metasurface devices,namely,metalenses,metacouplers,and metaholograms,which have empowered different forms of AR displays.Their physical principles,device designs,and the performance improvement of the associated AR displays are explained in details.In the end,we discuss the existing challenges of metasurface optics for AR display applications and provide our perspective on future research endea
基金supported by the National Basic Research Program of China(No.2012CB720003)the National Natural Science Foundation of China(No.61203151)
文摘In this paper, a new nonlinear augmented observer is proposed and applied to satellite attitude control systems. The observer can estimate system state and actuator fault simultaneously. It can enhance the performances of rapidly-varying faults estimation. Only original system matrices are adopted in the parameter design. The considered faults can be unbounded, and the proposed augmented observer can estimate a large class of faults. Systems without disturbances and the fault whose finite times derivatives are zero piecewise are initially considered, followed by a discussion of a general situation where the system is subject to disturbances and the finite times derivatives of the faults are not null but bounded. For the considered nonlinear system, convergence conditions of the observer are provided and the stability analysis is performed using Lyapunov direct method. Then a feasible algorithm is explored to compute the observer parameters using linear matrix inequalities （LMIs）. Finally, the effectiveness of the proposed approach is illustrated by considering an example of a closed-loop satellite attitude control system. The mance in estimating states and actuator faults. It also successfully. simulation results show satisfactory perfor- shows that multiple faults can be estimated
基金supported by the National Natural Science Foundation of China (71071016,70901005)the Fundamental Research Funds for the Central Universities (2009JBM040,2009JBZ012)the Foundation of State Key Laboratory of Rail Traffic Control and Safety (RCS2010ZT001)
文摘This paper presents an augmented network model to represent urban transit system.Through such network model,the urban transit assignment problem can be easily modeled like a generalized traffic network.Simultaneously,the feasible route in such augmented transit network is then defined in accordance with the passengers＇ behaviors.The passengers＇ travel costs including walking time,waiting time,in-vehicle time and transfer time are formulated while the congestions at stations and the congestions in transit vehicles are all taken into account.On the base of these,an equilibrium model for urban transit assignment problem is presented and an improved shortest path method based algorithm is also proposed to solve it.Finally,a numerical example is provided to illustrate our approach.
基金Air Force Office of Scientific Research(FA9550-14-1-0279)Goertek Electronics.
文摘Augmented reality(AR)displays are attracting significant attention and efforts.In this paper,we review the adopted device configurations of see-through displays,summarize the current development status and highlight future challenges in micro-displays.A brief introduction to optical gratings is presented to help understand the challenging design of grating-based waveguide for AR displays.Finally,we discuss the most recent progress in diffraction grating and its implications.
文摘Background:In recent years,the development of digital imaging technology has had a significant influence in liver surgery.The ability to obtain a 3-dimensional(3D)visualization of the liver anatomy has provided surgery with virtual reality of simulation 3D computer models,3D printing models and more recently holograms and augmented reality(when virtual reality knowledge is superimposed onto reality).In addition,the utilization of real-time fluorescent imaging techniques based on indocyanine green(ICG)uptake allows clinicians to precisely delineate the liver anatomy and/or tumors within the parenchyma,applying the knowledge obtained preoperatively through digital imaging.The combination of both has transformed the abstract thinking until now based on 2D imaging into a 3D preoperative conception(virtual reality),enhanced with real-time visualization of the fluorescent liver structures,effectively facilitating intraoperative navigated liver surgery(augmented reality).Data sources:A literature search was performed from inception until January 2021 in MEDLINE(Pub Med),Embase,Cochrane library and database for systematic reviews(CDSR),Google Scholar,and National Institute for Health and Clinical Excellence(NICE)databases.Results:Fifty-one pertinent articles were retrieved and included.The different types of digital imaging technologies and the real-time navigated liver surgery were estimated and compared.Conclusions:ICG fluorescent imaging techniques can contribute essentially to the real-time definition of liver segments;as a result,precise hepatic resection can be guided by the presence of fluorescence.Furthermore,3D models can help essentially to further advancing of precision in hepatic surgery by permitting estimation of liver volume and functional liver remnant,delineation of resection lines along the liver segments and evaluation of tumor margins.In liver transplantation and especially in living donor liver transplantation(LDLT),3D printed models of the donor’s liver and models of the recipient’s hilar anatom
文摘Intuitive and efficient interfaces for human- robot interaction （HRI） have been a challenging issue in robotics as it is essential for the prevalence of robots supporting humans in key areas of activities. This paper presents a novel augmented reality （AR） based interface to facilitate human-virtual robot interaction. A number of human-virtual robot interaction methods have been for- mulated and implemented with respect to the various types of operations needed in different robotic applications. A Euclidean distance-based method is developed to assist the users in the interaction with the virtual robot and the spatial entities in an AR environment. A monitor-based visualization mode is adopted as it enables the users to perceive the virtual contents associated with different interaction methods, and the virtual content augmented in the real environment is informative and useful to the users during their interaction with the virtual robot. Case researches are presented to demonstrate the successful implementation of the AR-based HRI interface in planning robot pick-and-place operations and path following operations.
基金Program for Changjiang Scholars and Innovative Research Team in UniversityDoctoral Program Foundation of Institutions of Higher Education of China (20060247028)
文摘Power augmented ram （PAR）engine is a popular equipment to reduce the requirement of power for takeoff and improve aerodynamic performance. To provide detailed insight into the aerodynamic characteristics of wing-in-ground effect （WIG）craft with PAR engine, numerical simulations are carried out on WIG craft models in cruise. Simplified engine models are applied to the simulations. Two cruise modes for PAR engine are considered. The aerodynamic characteristics of the WIG craft and other features are studied. Comparisons with WIG craft model without PAR show that shutoff of PAR engine results in an increase in drag and less change in lift. Accordingly for the work of PAR engine, the air flow blown from the engine accelerates the flow around the upper surface and a high-speed attached flow near the trailing edge is recorded. With the schemed PAR flow, more suction force is realized and the flow features over the wing vary noticeably. It is also shown that the Coanda effect,provided with an attached flow, introduces an appropriate and practical flow mode for WIG craft with PAR engine in cruise. The results refresh our understanding on aerodynamic characteristics of WIG craft.
基金the National Key R&D Plan of China[grant number 2017YFC1500906]the National Natural Science Foundation of China[grant number 41871323,41771442]+1 种基金Pre-research Project of Equipment Development Department[grant number 315050501]the Zhejiang Institute of Advanced Technology Chinese Academy of Sciences Special Fund Collaborative Innovation Project[grant number ZK-CX-2018-04].
文摘Flood visualization is an effective and intuitive tool for representing flood information from abstract spatiotemporal data.With the growing demand for flood disaster visualizations and mitigation,augmented flood visualizations that support decision makers’perspectives are needed,which can be enhanced by emerging augmented reality(AR)and 3D printing technologies.This paper proposes an innovative flood AR visualization method based on a 3D-printed terrain model and investigates essential techniques,such as the suitable size calculation of the terrain models,the adaptive processing of flood data,and hybridizing virtual flood and terrain models.A prototype experimental system(PES)based on the proposed method and a comparison experimental system(CES)based on a virtual terrain are developed to conduct comparative experiments,which combine the system performance and questionnaire method to evaluate the efficiency and usability of the proposed method.The statistical results indicate that the method is useful for assisting participants in understanding the flood hazard and providing a more intuitive and realistic visual experience compared with that of the traditional AR flood visualization method.The frame rate is stable at 60 frames per second(FPS),which means that the proposed method is more efficient than the traditional AR flood visualization method.
