基于VRML的数控机床的虚拟操作研究

虚拟环境下加工设备虚拟操作和虚拟加工是虚拟制造的一个重要研究内容。本文通过对数控机床的虚拟操作的研究,阐述了在VRML的虚拟现实应用平台上建立数控机床的虚拟操作系统的方法,提出了利用VRMLJavaAppletJavaScriptHtml多方相互通信的办法对VRML人机交互功能进行增强与扩展,从而满足数控机床虚拟操作的功能要求。实验结果表明,这种增强办法不仅使VRML原有的人机交互能力得到进一步的增强,并且为VRML添加了接收与处理文本信息以及读写文件等交互能力。此外,文中还提出了一种利用SolidWork与PolyTrans相互结合而实现的在虚拟环境下的数控机床的快速建模方法,并取得令人满意的效果。本系统不但可应用于异地制造、数控机床加工仿真,还可应用于基于WEB的数控机床操作、编程与加工培训等方面。     

A Survey on 3D Virtual Object Manipulation: From the Desktop to Immersive Virtual Environments

Interactions within virtual environments often require manipulating 3D virtual objects. To this end, researchers have endeavoured to find efficient solutions using either traditional input devices or focusing on different input modalities, such as touch and mid‐air gestures. Different virtual environments and diverse input modalities present specific issues to control object position, orientation and scaling: traditional mouse input, for example, presents non‐trivial challenges because of the need to map between 2D input and 3D actions. While interactive surfaces enable more natural approaches, they still require smart mappings. Mid‐air gestures can be exploited to offer natural manipulations mimicking interactions with physical objects. However, these approaches often lack precision and control. All these issues and many others have been addressed in a large body of work. In this article, we survey the state‐of‐the‐art in 3D object manipulation, ranging from traditional desktop approaches to touch and mid‐air interfaces, to interact in diverse virtual environments. We propose a new taxonomy to better classify manipulation properties. Using our taxonomy, we discuss the techniques presented in the surveyed literature, highlighting trends, guidelines and open challenges, that can be useful both to future research and to developers of 3D user interfaces.     

Helical‐Like 3D Ultrathin Piezoelectric Element for Complicated Ultrasonic Field

The developments of personalized medicine, ultrasound imaging, and contactless “microscopic handle” techniques are pushing ultrasonic transducers toward features of high frequency, device miniaturization, and even novel function. However, the conventional ultrasonic transducer has severely limited the development of novel ideas for applications due to its ordinary ultrasonic field. Although transducer arrays and monolithic acoustic holograms are capable of producing the complicated ultrasonic field, it is still difficult to achieve high frequency, device miniaturization, and novel function simultaneously. Here, a simple but effective approach is introduced that aims at reconstructing the complicated and high‐frequency ultrasonic field via a compact single‐element ultrasonic transducer. The 3D ultrathin piezoelectric element with a complex configuration is demonstrated theoretically and experimentally to produce the desired complicated ultrasonic field. With helical‐like configuration, the single‐element ultrasonic transducer offers efficient noncontact trapping and manipulation of suspended microparticles and biological cells. Moreover, its strong trapping capability leads to the 3D stacking of microparticles, which is a novel and interesting phenomenon achieved by a single‐element ultrasonic transducer. This work brings the possibility of a complicated ultrasonic field for achieving novel high‐frequency ultrasound applications through the design of smart structure ultrathin piezoelectric materials.     

微波段超构表面对电磁波波前的调控研究

文章回顾总结了本课题组近期关于微波段超构表面的研究进展。首先推导了单层超构表面的透射效率极限值,并设计实现了对交叉圆极化电磁波波前的有效人工调控。进一步基于等效滤波器的理论模型,推导了多层超表面的基本结构特性,在此基础上设计了能够分别工作于线极化及圆极化入射波条件下的多层超构透镜,实现了微波涡旋波束的高效激发,以及对正交圆极化的内在对称性进行人为解耦等多重波前调控。经过一系列的仿真分析和实验验证,我们所设计的微波段单层、多层超构表面均可产生符合预期理论设计的调控结果。这些研究进展为电磁波调控器件的平面化提供了有效的理论依据,加快了超构表面在无线通信技术领域的应用和发展。     

Intracellular Fate of Hydrophobic Nanocrystal Self‐Assemblies in Tumor Cells

Control of interactions between nanomaterials and cells remains a biomedical challenge. A strategy is proposed to modulate the intralysosomal distribution of nanoparticles through the design of 3D suprastructures built by hydrophilic nanocrystals (NCs) coated with alkyl chains. The intracellular fate of two water‐dispersible architectures of self‐assembled hydrophobic magnetic NCs: hollow deformable shells (colloidosomes) or solid fcc particles (supraballs) is compared. These two self‐assemblies display increased cellular uptake by tumor cells compared to dispersions of the water‐soluble NC building blocks. Moreover, the self‐assembly structures increase the NCs density in lysosomes and close to the lysosome membrane. Importantly, the structural organization of NCs in colloidosomes and supraballs are maintained in lysosomes up to 8 days after internalization, whereas initially dispersed hydrophilic NCs are randomly aggregated. Supraballs and colloidosomes are differently sensed by cells due to their different architectures and mechanical properties. Flexible and soft colloidosomes deform and spread along the biological membranes. In contrast, the more rigid supraballs remain spherical. By subjecting the internalized suprastructures to a magnetic field, they both align and form long chains. Overall, it is highlighted that the mechanical and topological properties of the self‐assemblies direct their intracellular fate allowing the control intralysosomal density, ordering, and localization of NCs.     

面向重力加速度测量领域的原子干涉操控方法综述

原子干涉重力仪凭借高精度小型化的优势,在高精度重力测量方面具有良好的发展前景。目前原子干涉重力仪在使用过程中,通常使用传统拉曼三脉冲方法对原子团进行分束合束的干涉操控,但不同的干涉操控方法会导致最终原子干涉条纹的测量精度的不同。介绍了几种原子干涉的操控方法,在传统原子干涉操控方法的基础上,增大原子干涉闭合回路的干涉面积,进而能够提高原子干涉条纹的分辨率。对这几种方法进行了比较,分析了每种方法需要的实验条件,得出了几种原子干涉操控方法对原子干涉重力仪的测量的影响。提出了提高原子干涉重力仪测量精度的建议,为后续更高精度的原子干涉重力仪的研究提供了参考。     

Quantitative analysis and evaluation of manipulation comfort of tractor gear shifting based on combined methods

Currently, studies of the manipulation comfort of agriculturalmachinery are mainly based on qualitative analysis and subjective evaluation. This study is mainly focused on the quantitative analysis and evaluation of the manipulation comfort of tractor gear‐shifting. By taking various factors into account, a combined evaluation model and the corresponding indicator system were proposed based on the method of maximizing deviations. The data of pedal force and stroke length of the clutch were collected from eight different types of agricultural tractors, which were used as the basic data for subsequent analyses. Then, five evaluation methods, including principal component analysis (PCA), comprehensive evaluation based on the entropy, ideal solution (TOPSIS), improved TOPSIS and grey correlation analysis, were adopted to evaluate the manipulation comfort of tractor gear‐shifting. A consistency check on the evaluation results of the five methods was conducted by using the concordance coefficient method of KENDALL. Furthermore, the combined weight vector of the compatible method set was calculated by maximizing the deviations. Through comparison, we found that the evaluation results of the combined methods were consistent with the subjective evaluation results. The method of combined evaluation can compensate for the insufficiency of single methods and overcome the inconsistency of the evaluation, and thus can produce more objective and accurate results. Our results can provide references for the quantitative research of manipulation comfort of agricultural machinery equipment.     

Perception,navigation, and manipulation in the team KAUST approach to the MBZIRC ground robotics challenge

The ground robotics challenge in the Mohammed Bin Zayed International Robotics Challenge required a ground vehicle equipped with a robotic arm to autonomously locate a panel, select a proper size wrench among several options mounted on the panel, and use the wrench to rotate a valve. Autonomy was the critical factor in this challenge, which required the teams to devise algorithms that can operate successfully in a semistructured environment without human supervision. This paper presents the approaches taken by team KAUST to meet this challenge, ranging from in‐house hardware designs to algorithm integration and customization. We separated the whole objective into three interconnected tasks: Navigation, perception, and manipulation. For the navigation task, we developed a basic robotic exploration scheme to find the panel front side where the wrenches were present. For the perception task, we integrated common object detection algorithms with neural networks to identify the proper size wrench precisely. For successful manipulation, we designed and built a custom gripper, which was inspired by the common grasping behavior of a human hand under tight clearance conditions. The modular structure of the proposed approach allowed the team to progress in several subtasks simultaneously. However, the interconnection between the subtasks necessitated a reliable integration framework between these modules for effective implementation. We tuned our algorithms in extensive experimental studies and eventually obtained 10 consecutive successful navigation runs, 96% true wrench detection rate, and high success rate in wrench grasping. Furthermore, successful complete tests proved the reliability and repeatability of our system.     

Team NimbRo at MBZIRC 2017: Fast landing on a moving target and treasure hunting with a team of micro aerial vehicles

The Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2017 has defined ambitious new benchmarks to advance the state‐of‐the‐art in autonomous operation of ground‐based and flying robots. This study covers our approaches to solve the two challenges that involved micro aerial vehicles (MAV). Challenge 1 required reliable target perception, fast trajectory planning, and stable control of an MAV to land on a moving vehicle. Challenge 3 demanded a team of MAVs to perform a search and transportation task, coined “Treasure Hunt,” which required mission planning and multirobot coordination as well as adaptive control to account for the additional object weight. We describe our base MAV setup and the challenge‐specific extensions, cover the camera‐based perception, explain control and trajectory‐planning in detail, and elaborate on mission planning and team coordination. We evaluated our systems in simulation as well as with real‐robot experiments during the competition in Abu Dhabi. With our system, we—as part of the larger team NimbRo—won the MBZIRC Grand Challenge and achieved a third place in both subchallenges involving flying robots.