Relative Attitude and Position Estimation for Spacecraft from Multiple Geometric Features

This paper investigates the pose and motion estimation problem using single camera measurement for spacecraft. The leader spacecraft of three-dimensional shape is observed by a calibrated camera fixed on the follower spacecraft. Based on dual numbers, an integrated observation model is proposed based on a combination of multiple geometric features including points, lines and circles, which can improve the robustness and accuracy of the estimation algorithm. A six-degree-of-freedom relative motion model is proposed by using the dual quaternion representation, in which the rotation-translation coupling effect due to the points deviating from the center of the mass is described. Employing the proposed observation model and dynamics model, an Extended Kalman Filter is presented to estimate the relative state between the two spacecraft. Numerical simulations are performed to evaluate the proposed approaches, showing the convergence of relative estimation errors and superior estimation performance.     

How to model and implement connections between physical and virtual models for digital twin application

Digital twin (DT) is a virtual mirror (representation) of a physical world or a system along its lifecycle. As for a complex discrete manufacturing system (DMS), it is a digital model for emulating or reproducing the functions or actions of a real manufacturing system by giving the system simulation information or directly driven by a real system with proper connections between the DT model and the real-world system. It is a key building block for smart factory and manufacturing under the Industry 4.0 paradigm. The key research question is how to effectively create a DT model during the design stage of a complex manufacturing system and to make it usable throughout the system’s lifecycle such as the production stage. Given that there are some existing discussions on DT framework development, this paper focuses on the modeling methods for rapidly creating a virtual model and the connection implementation mechanism between a physical world production system at a workshop level and its mirrored virtual model. To reach above goals, in this paper, the discrete event system (DES) modeling theory is applied to the three-dimension DT model. First, for formally representing a manufacturing system and creating its virtual model, seven basic elements: controller, executor, processor, buffer, flowing entity, virtual service node and logistics path of a DMS have been identified and the concept of the logistics path network and the service cell is introduced to uniformly describe a manufacturing system. Second, for implementing interconnection and interaction, a new interconnection and data interaction mechanism between the physical system and its virtual model for through-life applications has been designed. With them, each service cell consists of seven elements and encapsulates input/output information and control logic. All the discrete cells are constructed and mapped onto different production-process-oriented digital manufacturing modules by integrating logical, geometric and data models. As a result, the virtual-physical connection is realized to form a DT model. The proposed virtual modeling method and the associated connection mechanism have been applied to a real-world workshop DT to demonstrate its practicality and usefulness.     

Digital twin-based industrial cloud robotics: Framework,control approach and implementation

Industrial cloud robotics (ICR) integrates cloud computing with industrial robots (IRs). The capabilities of industrial robots can be encapsulated as cloud services and used for ubiquitous manufacturing. Currently, the digital models for process simulation, path simulation, etc. are encapsulated as cloud services. The digital models in the cloud may not reflect the real state of the physical robotic manufacturing systems due to inaccurate or delayed condition update and therefore result in inaccurate simulation and robotic control. Digital twin can be used to realize fine sensing control of the physical manufacturing systems by a combination of high-fidelity digital model and sensory data. In this paper, we propose a framework of digital twin-based industrial cloud robotics (DTICR) for industrial robotic control and its key methodologies. The DTICR is divided into physical IR, digital IR, robotic control services, and digital twin data. First, the robotic control capabilities are encapsulated as Robot Control as-a-Service (RCaaS) based on manufacturing features and feature-level robotic capability model. Then the available RCaaSs are ranked and parsed. After manufacturing process simulation with digital IR models, RCaaSs are mapped to physical robots for robotic control. The digital IR models are connected to the physical robots and updated by sensory data. A case is implemented to demonstrate the workflow of DTICR. The results show that DTICR is capable to synchronize and merge digital IRs and physical IRs effectively. The bidirectional interaction between digital IRs and physical IRs enables fine sensing control of IRs. The proposed DTICR is also flexible and extensible by using ontology models.     

基于国产FPGA及DAC的任意波形发生器的设计

任意波形发生器作为测试测量设备的一种重要仪器,在航空航天的测量与控制技术领域中得到了广泛应用;当前市场成熟任意波形发生器产品多为国外产品或者国内厂商基于国外FPGA和DAC研制的产品;为了打破技术垄断,提高国产任意波形发生器的自主技术保障能力,研制基于国产芯片的任意波形发生器愈发重要;随着国产芯片设计技术提升,国产FPGA和DAC的性能显著提高,并得到了广泛应用;PXI总线作为当前仪器领域的主要总线类型之一,可以满足大部分测试仪器的通讯要求;基于国产FPGA和DAC器件,从硬件设计和软件设计两个方面出发,成功研制了一款采样率为100 MSa/s的 PXI总线任意波形发生器模块,实现了43 MHz信号输出,通过实验测试了模块的功能和性能,完全满足模块指标要求,充分证明了国产芯片在工程设计中的性能特性。     

我国惯性仪器仪表的技术特点及发展综述

惯性仪器仪表技术已成为衡量一个国家科学技术水平和国防实力的重要标志之一。现今,国防领域和民用市场的旺盛需求极大的促进了惯性仪器仪表的发展,需求牵引成为惯性仪器仪表发展的源动力。本文简述了我国惯性仪器仪表的发展历史,总结了我国惯性仪器仪表的最新发展现状,分析了该行业的行业特点,并对未来市场需求进行了预测。     

Degradation‐shock‐based Reliability Models for Fault‐tolerant Systems

Reliability modeling of fault‐tolerant systems subject to shocks and natural degradation is important yet difficult for engineers, because the two external stressors are often positively correlated. Motivated by the fact that most radiation‐induced failures are contributed from these two external stressors, a degradation‐shock‐based approach is proposed to model the failure process. The proposed model accommodates two kinds of failure modes: hard failure caused by shocks and soft failure caused by degradation. We consider a generalized m–δ shock model for systems with fault‐tolerant design: failure occurs if the time lag between m sequential shocks is less than δ hours or degradation crosses a critical threshold. An example concerning memory chips used in space is presented to demonstrate the applicability of the proposed model. Copyright © 2015 John Wiley & Sons, Ltd.     

用于复合材料的超声测厚传感器设计

复合材料作为一种优异的耐磨和耐高温材料,在高温设备热防护、飞机刹车制动盘等军事、特种民用技术等领域有着广泛的应用.为了更好地测量和评定这一类型材料的防护特性,迫切需要一种能够在试验中进行厚度动态测量的传感器.超声式厚度测量传感器具有无损、无放射性的优点,并且可以提供实时动态的测量结果,为这种类型材料的测量提供了强有力的...     

反弹道斜撞击下自由梁结构响应研究

反弹道撞击实验在材料与结构动力学响应研究领域中已有广泛应用,相比正向撞击实验,反弹道实验可在自由梁上加装测量装置,得到更精确的测试结果。开展了自由梁20°斜撞击的反弹道实验,使用数字图像相关方法测试了弹体的实时动态响应情况,引入失效判据,并结合数值模拟分析,求解了轴向与横向载荷交互作用下的自由梁弯曲形貌。结果表明：考虑轴向力的计算结果与实验吻合较好,且优于文献［4］给出的自由梁计算模型;当质量比m_γ≥10时,正反弹道具有较好的等效性,该方法亦可用于求解弹体在非正侵彻过程中的结构响应。     

Visualization and performance measurement of operating mesh-wicked heat pipes

This work presents visualization of the evaporation/boiling process and thermal measurements of operating horizontal transparent heat pipes. The heat pipes consisted of a two-layered copper mesh wick consisting of 100 and/or 200 mesh screens, a glass tube and water as the working fluid. Experimental results indicated that nucleate boiling was prompted for a wick having a fine 200-mesh bottom layer. When the fluid charge approximately equaled the pore volume in the wick, the water–vapor interface receded into more curved menisci with increasing heat load Q. Thus, larger capillary forces and evaporation areas were attained to meet the increasing need of liquid supply and evaporation rate at the water–vapor interface. At Q = 40 and 45 W, the water film became less than 100 μm and the nucleate boiling observed at lower heat loads disappeared. Optimal thermal characteristics with smallest thermal resistances across the evaporator and lowest overall temperature distributions were found for such a wick/charge combination. Under a smaller charge, partial dry-out was observed in the evaporator. Under a larger charge, liquid recession with increasing heat load was limited and bubbles grew and burst violently at high heat loads. The effects of different wicks and fluid charges on the evaporation/boiling characteristics were discussed.     

面向微组装单元的数字孪生同步方法及系统实现

为了解决微组装生产线数字化转型面临的数据处理难和设备信息化控制难的问题,设计了微组装生产线单元数字孪生系统架构,提出一种基于实时生产数据的四维融合模型孪生同步方法,从行为实时映射、状态实时映射和动作实时映射的角度对孪生同步进行了诠释,并对其关键技术——多源异构数据分类、清洗与解析和实时数据驱动四维融合孪生模型进行了详细...