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Co-axial depth sensor with an extended depth range for AR/VR applications

DOI:10.3724/SP.J.2096-5796.2019.00027

Accepted Date:2019-11-07

Abstract (7) | PDF (2)

Background     Depth sensor is an essential element in virtual and augmented reality devices to digitalize users’ environment in real time. The current popular technologies include the stereo, structured light, and Time-of-Flight (ToF). The stereo and structured light method require a baseline separation between multiple sensors for depth sensing, and both suffer from a limited measurement range. The ToF depth sensors have the largest depth range but the lowest depth map resolution. To overcome these problems, we propose a co-axial depth map sensor which is potentially more compact and cost-effective than conventional structured light depth cameras. Meanwhile, it can extend the depth range while maintaining a high depth map resolution. Also, it provides a high-resolution 2D image along with the 3D depth map.   Methods This depth sensor is constructed with a projection path and an imaging path. Those two paths are combined by a beamsplitter for a co-axial design. In the projection path, a cylindrical lens is inserted to add extra power in one direction which creates an astigmatic pattern. For depth measurement, the astigmatic pattern is projected onto the test scene, and then the depth information can be calculated from the contrast change of the reflected pattern image in two orthogonal directions. To extend the depth measurement range, we use an electronically focus tunable lens at the system stop and tune the power to implement an extended depth range without compromising depth resolution. Results  In the depth measurement simulation, we project a resolution target onto a white screen which is moving along the optical axis and then tune the focus tunable lens power for three depth measurement subranges, namely, near, middle and far. In each sub-range, as the test screen moves away from the depth sensor, the horizontal contrast keeps increasing while the vertical contrast keeps decreasing in the reflected image. Therefore, the depth information can be obtained by computing the contrast ratio between features in orthogonal directions. Conclusions  The proposed depth map sensor could implement depth measurement for an extended depth range with a co-axial design.

A review of cable layout design and assembly simulation in virtual environments

DOI:10.3724/SP.J.2096-5796.19.00005

Accepted Date:2019-11-07

Abstract (6) | PDF (2)

The layout and assembly of flexible cables play important roles in the design and development of complex electromechanical products. The rationality of cable layout design and the reliability of cable assembly greatly affect product quality. In this paper, we review the methods of cable layout design, cable assembly process planning and cable assembly simulation. We first reviews research on flexible cable layout design (both interactive and automatic). Then, research on the cable assembly process planning, including cable assembly path and manipulation planning, is reviewed. Finally, cable assembly simulation is introduced, which includes general cable information, cable collision detection data, and cable assembly process modeling. Current problems and future research directions are summarized at the end of the paper.

3D Virtual-Real Mapping of aircraft automatic spray operation and online simulation monitoring

DOI:10.3724/SP.J.2096-5796.19.00011

Accepted Date:2019-11-07

Abstract (5) | PDF (1)

Aiming at the lack of closed-loop feedback and optimization enabling tools in aircraft automatic spraying system at present, 3D virtual-real mapping technique, namely digital twin, of the automatic spraying system is studied systematically in this paper. With the sensors installed in the spraying system, the spraying working parameters are collected on-line and are used to drive the three-dimension virtual spraying system to realize the total-factor monitoring of the spraying operation. Furthermore, the Operation Evaluation Model is applied to the analysis and management of the key indexes of spraying quality. That is, once the data value of the key indexes is over the threshold, the operation will be optimized automatically. The results of a case study show that the above approach can well support the high-efficiency analysis, evaluation and optimization of the spraying operation process.

Digital assembly technology based on augmented reality and digital twin: a review

DOI:10.3724/SP.J.2096-5796.19.00018

Accepted Date:2019-11-07

Abstract (5) | PDF (0)

Product assembly simulation is considered as one of the key technologies in the process of complex product design and manufacturing. Virtual assembly realizes the assembly process design, verification and optimization of complex products in the virtual environment, which plays an active and effective role in improving the assembly quality and efficiency of complex products. In recent years, augmented reality (AR) and digital twin(DT) technology have brought new opportunities and challenges to the digital assembly of complex products due to their characteristics of virtual reality fusion and interactive control. This paper expounds the concept and connotation of AR, enumerates a typical AR assembly system structure, analyzes the key technologies and applications of AR in digital assembly, and points out that DT technology is the development trend of intelligent assembly research in the future.

The research of ghost suppression method in polarized catadioptric virtual reality optical system

DOI:10.3724/SP.J.2096-5796.19.00021

Accepted Date:2019-10-11

Abstract (10) | PDF (2)

In this paper, a polarized catadioptric virtual reality optical system is introduced. Aiming at the problem of serious ghost image in the system, the causes are analyzed based on the design principles and optical structure. The distribution of stray light is simulated by using Lighttools, and three major ghost paths are selected by using the area of diffuse spot,  and the energy ratio of stray light, K as the evaluation ways. A method to restrain ghost image by optimizing the structure of optical system by controlling the focal power of ghost image path is proposed. The results show that the  of ghost image path increases by 40% and K decreases by 40% compared with before optimization. Ghost image is effectively suppressed, which provides theoretical basis and technical support for ghost suppression in virtual reality optical system.

Research on visual element of augmented reality assembly process

DOI:10.3724/SP.J.2096-5796.2019.0029

Accepted Date:2019-09-25

Abstract (16) | PDF (5)

In order to solve the problem of visualization in augmented reality (AR) for assembly process information, this paper studies the composition of AR assembly process information. And the visual elements of assembly process are classified as six categories. According to the expression characteristics of visual element for assembly process information in AR environment, the standard visual elements of assembly process are designed and the visual element layout principles are studied. Finally, the typical visualization elements are presented by an AR based assembly instruction system.

Edge vector based large graph visualization and interactive exploration

DOI:10.3724/SP.J.2096-5796.2019.0010

Accepted Date:2019-03-22

Abstract (183) | PDF (21)

The demand for graph analysis is increasing. High quality and high readability graph layout is important for graph analysis. In the past years, we investigate this topic and propose a unified framework for graph layout and exploration. This framework maintains the readability during layout and interaction process. It controls the edge lengths and directions instead of only lengths. We can model most existing layout constraints, as well as develop new ones. For interactive exploration on the detail of a graph, we extend our framework to a new focus + context fisheye view. Traditional fisheye views for exploring large graphs introduce substantial distortions that often lead to a decreased readability of paths and other interesting structures. We use edge directions as constraints for graph layout optimization allows us not only to reduce spatial and temporal distortions during fisheye zooms, but also to improve the readability of the graph structure. Furthermore, the framework enables us to optimize fisheye lenses towards specific tasks and design a family of new lenses. We implement our framework with GPU parallel computing, which allows us process large graphs with up to 10,000 nodes at interactive rates.