Shenyang Institute of Automation,Chinese Academy Of Sciences
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A novel attention-based domain adaptation model for intelligent bearing fault diagnosis under variable working conditions
No full textIn recent years, transfer learning technology has developed rapidly and has been widely used in bearing fault diagnosis. Most existing methods mainly align the overall feature distribution of the signal samples across the source and target domains. However, the transferability of each signal and each segment of a signal sample is different. Therefore, in this paper, a novel attention-based domain adaptation model (ADA) is proposed. The ADA model consists of a feature extractor and an ADA module. The feature extractor is built by separable convolution with channel attention module and length attention module to improve the reliability of feature learning. The ADA module consists of two parts, the local ADA module and the global ADA module to enhance the model's domain adaptation ability by focusing on the signals and signal segments with better transferability. The experimental results show that the ADA model is superior to other intelligent fault diagnosis methods based on transfer learning under variable working conditions.</p
Effect of laser shock wave on the thermal corrosion resistance of single crystal alloy
No full text针对镍基单晶高温合金叶片服役时受高温腐蚀工作环境极易疲劳断裂问题，研究了不同冲击次数下激光冲击强化对单晶合金抗热腐蚀性能的影响。利用显微硬度仪测量了激光冲击前后合金纵截面的显微硬度；借助扫描电子显微镜和能谱仪观察和分析腐蚀层表面及纵截面的微观组织，并结合X射线衍射仪确定腐蚀层表面相结构。结合对10 h后不同激光冲击次数下合金的热腐蚀动力学曲线的分析，实验结果表明：合金经激光冲击强化后，合金表面显微硬度和截面硬度的深度均随着激光冲击次数的增加而增大；合金在短时热腐蚀实验中，当激光冲击次数从0次增加到1次、2次、3次后，合金腐蚀最大单位面积增重量分别从2.87 mg?cm-2降低到2.17 mg?cm-2、1.81 mg?cm-2和1.10 mg?cm-2，腐蚀层深度分别从91μm降低到65μm、41μm和27μm，并且表面腐蚀坑的大小、深度和数量明显减少，保护性氧化膜致密性得到提高。表明激光冲击强化能够有效提高900℃/75%Na2SO4-25%Na Cl盐膜条件下单晶合金的抗热腐蚀性能。</p
Multifunctional thermo-magnetically actuated hybrid soft millirobot based on 4D printing
No full textSoft materials, which use both internal energy change and external energy supply to produce shape morphing and motion, are essential for the development of robotics. Four-dimensional (4D) printing is a promising method for fabricating soft robots with arbitrary structures. However, there are still few hybrid soft robots that can be manufactured by 4D printing because of the physicochemical nature of the materials. In this study, a novel smart hydrogel composed of NIPAM, Laponite nanoclay, and NdFeB magnetic particles, which have simultaneous temperature sensation and magnetic actuation, was synthesized for 4D printing of robots. It has been proven that this material has good mechanical properties and excellent machinability and biocompatibility. Soft millirobots with different structures and functions were printed, including a catheter with a multi-segment magnetic head, a leptasteria-like robot, and a shellfish-like robot, which can respond to both magnetic and thermal fields. The locomotion of the millirobot has been verified to overcome physical obstacles in the human stomach model and complete active transportation of cargo. The synergistic responses to the magnetic field and thermal field make the robot more adaptable and reduce the leakage of drugs during transportation. The 4D printed soft millirobots will promote the application prospects of robots in the fields of bioengineering and medical treatment
Multi-hop D2D relay-assisted transmission and outage analysis for industrial 5G
No full text面向工业5G网络的超可靠强实时传输要求，研究基于设备到设备通信(Device-to-Device,D2D)的多跳多中继辅助传输方法。基于随机几何理论，采用泊松点过程对工业现场设备进行建模，并划分中继选择区域。多跳中继过程中，每一跳中继选择信干噪比最大的节点进行解码转发。充分考虑层叠部署的多条D2D传输路径上的节点干扰以及随机噪声，推导出端到端中断概率的闭式表达式。仿真分析了中继节点部署密度、发射功率、路径距离等因素对端到端中断概率的影响。结果表明，采用多跳多中继辅助的D2D传输可以大幅降低工业5G网络的端到端中断概率，提高传输可靠性。</p
Customized construction of microscale multi-component biostructures for cellular applications
No full textIn vitro biofabrication is employed in fields such as biomedicine and those using biomimetic materials. However, it suffers from drawbacks such as low resolution, applicability on a limited range of components, and difficulty in purposefully depositing specific cells in three-dimensional space. Hence, this paper proposes a digital micromirror device-based optical projection lithography (DOPL) system for producing multi-component microstructures with resolutions of tens of microns and explores the behavior of cells with these structures. The printability and mechanical properties of these microstructures were investigated to assess their reproduction quality and the ability to control their structural characteristics. The results show that when DOPL is used with polyethylene glycol dimethacrylate (PEGDMA) hydrogel, an array of micropits can be fabricated within a few minutes. Furthermore, uniform cell spheroids form rapidly with high throughput when they are seeded into the micropits. Additionally, PEGDMA and gelatin methacryloyl (GelMA) were used to construct multi-component microstructures, and it was demonstrated that cells with various morphologies selectively adhere to the heterogeneous interface. In addition, DOPL could enable deposition of various cells for constructing microenvironments and for drug screening. Finally, a biomimetic peritoneal model was constructed. Overall, this work demonstrates the versatility of this system and its potential in cellular applications such as cell behavior research, drug screening, and tissue engineering.</p
Review of Space Manipulator Control Technologies
No full text考虑到空间机械臂在执行在轨维修、在轨组装、在轨加注等复杂危险的空间任务时，其精准、灵巧的操控技术的重要性，从不同类型空间机械臂构形、末端执行器出发，分析了空间机械臂的发展趋势。综述了空间机械臂操控过程中涉及的5项关键技术，包括：交会对接与捕获技术、自主规划与智能控制技术、传感与感知技术、智能协同与操控技术及系统安全保障技术。最后，就现有的空间机械臂在操控过程中面临的问题，提出未来的发展方向及展望。</p
Cascaded effect in a high-peak-power terahertz-wave parametric generator
No full textWe demonstrate megawatt-level terahertz (THz)-wave generation via a Stokes-seed-injected THz-wave parametric generator and study the cascaded effect. The optical-to-THz conversion efficiency was 1.72 × 10−3, and the peak power was conservatively estimated to be 1.09 MW using the pulse width of the pump. More than 80% of the THz-wave energy came from primary parametric generation, with the rest coming from high-order parametric amplification. Clear cascaded Stokes spots of second to fourth order were observed, and the factors affecting the high-order parametric process are discussed. The cascaded parametric effect is beneficial for achieving a higher optical-to-THz conversion efficiency, thereby improving the performance of high-peak-power THz-wave parametric sources.</p
Towards a general design evaluation tool: The development and validation of a VPP for autonomous sailing monohulls
No full textSailing speed performance is a crucial indicator that significantly affects the trafficability, efficiency, and tracking capability of autonomous sailing monohulls during marine science missions. Considering that the design of the hull and keel of an autonomous sailing monohull is usually a task-orientated and creative process, estimating speed performance by traditional velocity prediction programs (VPPs) based on empirical formulas and gradient solvers will lead to errors. This paper proposes a generalized VPP for helping designers assess the speed performance of their autonomous sailing monohulls. We designed an enhanced genetic algorithm (GA) solver to help the VPP converge quickly without a priori performance estimation. Furthermore, we propose an innovative neighbourhood information-based optimization (NIBO) strategy to accelerate and refine the solutions using adjacent states (external conditions with the same true wind speed (TWS) or true wind angle (TWA)) instead of culminating prediction by solving each state independently. We provide an application of the proposed VPP on our prototype as an example. Moreover, the numerical and experimental results show that the proposed VPP can serve as a practical design evaluation tool, especially in the early stages of design.</p
Static and dynamic performances of sandwich plates with magnetorheological elastomer core: Theoretical and experimental studies
No full textThis paper investigates the static and dynamic performances of sandwich plates with magnetorheological elastomer (MRE) core, in which the MRE core includes two copper wire layers, two inner metal layers, and one MRE layer. First, based on the complex modulus method, the Jolly theory and the pre-defined magnetic coefficients, the dynamic moduli, and loss factors of MRE are assumed as a function of magnetic induction intensity. Furthermore, a theoretical model of the MRE sandwich plates (MRESPs) is proposed, which considers the internal magnetic field excitation and four types of panel materials, namely fiber-reinforced polymer (FRP), fiber-reinforced polymer with carbon nanotubes (CNT-FRP), metal and fiber-metal hybrid (FMH) panels. After the deformation and energy equations are derived to solve the static bearing stiffness, dynamic stiffness, and damping parameters, some literature results are employed to provide the initial validation of the model developed. Subsequently, four MRESP specimens with the FRP, CNT-FRP, metal, and FMH panels are fabricated and measured to further verify the model as well as to evaluate the mechanical performance. The influence of critical geometric and material parameters related to MRE on static and dynamic properties is also discussed to summarize some practical conclusions for engineering applications.</p
An optimal visual servo trajectory planning method for manipulators based on system nondeterministic model
No full textWhen a manipulator captures its target by a visual servo system, uncertainties can arise because of mechanical system and visual sensors exist error. This paper proposes an intelligent method to predict the successful rate for a manipulator to capture its target with motion and sensor errors. Because the mapping between the joint space of the manipulator and the Cartesian space at the end of the manipulator is nonlinear, when there is a bounded error of the manipulator's joint, the error range of the end motion is constantly changing with the different joint positions. And at the same time, the visual servo camera will also measure the target from different positions and postures, so as to produce measurement results with different error ranges. The unknown time-varying error property not only greatly affects the stability of the closed-loop control but also causes the capture failure. The purpose of this paper is to estimate the success probability of different capture trajectories by establishing the nondeterministic model of manipulator control system. First, a system model including motion subsystem and feedback subsystem was established with system error described by Gaussian probability. And then Bayesian estimation was introduced into the system model to estimate the executing state of the predefined trajectory. Linear least quadratic regulators (LQR) control is used to simulate the input correction in the closed-loop control between motion subsystem and feedback subsystem. At last, the successful probability of capturing the target is established by the Gaussian distribution at the end point of the trajectory with geometric relationship calculation between tolerance range and error distribution. The effectiveness and practicability of the proposed method are proved by simulation and experiment.</p