Shenyang Institute of Automation,Chinese Academy Of Sciences
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Multi-scale simulation of microstructure evolution during direct laser deposition of Inconel718
No full textAs a free forming additive manufacturing technology for high performance metal parts, laser deposition manufacturing has a broad application prospect in aerospace and other fields. The solidification behavior and microstructure of molten pool determine the mechanical properties of the deposited parts. A multi-scale Cellular Automaton (CA)- Finite Element (FE) model is developed to simulate the microstructure evolution with different process parameters during the Direct Laser Deposition (DLD) process. Temperature data and solidification parameters under different process parameters are obtained by finite element method, which establish connections between macroscopic temperature field and microstructure simulation. In addition, the effects of different process parameters on dendrite morphology, element segregation and grain structure are investigated. The primary dendrite arm spacing (PDAS), Nb element precipitation and grain size all increase with the increase of laser power, which are caused by the decrease of cooling rate. Moreover, the trend of the simulated results of microstructure under various process parameters are consistent with the experimental results.</p
Effects of square spot size and beam quality on residual stress of 7050 aluminum alloy by laser shock peening
No full textLaser shock peening is a promising surface modification technology to improve the properties of metal. In this work, the spatial distribution model of the shock wave pressure induced by laser shock peening was proposed by matching the pit profile. The relationship between laser beam quality and shock wave pressure distribution was analyzed. And the shock wave pressure profile changes caused by the lateral expansion of plasma were quantitatively calculated. Results showed that the proportions of the flat-topped part and the edge gradient part of the pits formed by different spot sizes are basically the same. As the spot size increases, the range of residual stress increases. Compared with the flat-topped part length of the beam quality profile, the flat-topped part length of the shock wave pressure profile is reduced by about 14% due to lateral expansion of the plasma. Simulated residual stress and deformation profiles are in an agreement with the measured data in all cases.</p
Study on reducing burrs of super alloy through structures in water jet guided laser ablation
No full textWith the increase of thrust-weight ratio of aero-engine, the working temperature of core parts is becoming higher and higher. In order to improve the service life of core parts, many high-precision micro holes are machined on those core parts. To realize the fabrication of micro hole with less burrs on super alloy substrates, a novel water jet guided laser processing method is proposed in this paper. A material removal principle based on plasma detonation assistant machining is proposed and proved to be valid through experiments. Then a laser-induced plasma assisted ablation method using sacrificial layer in the machining of through holes and grooves on super alloy is approved. This method can get higher machining efficiency and avoid longtime trimming in subsequent experiments. The size of burrs in through hole decreases 57.89%, while the area of burrs decreases 42.32% after using 304 stainless steel as sacrificial layer in the machining of through hole. Grooves with fewer burrs are also achieved on super alloy with this method. That method can also be used to fabricate a variety of functional structures.</p
TA15 and inconel 625 bimetallic structures additive manufacturing and phased array ultrasonic testing
No full textAdditive manufacturing of bimetallic structures has become a hotspot in recent years. However, the interfaces of bimetallic structures are always the weaknesses, and cracks always occur at the interfaces. Three bimetallic samples of TA15 and Inconel 625 were manufactured by laser metal deposition, and the effect of laser power on the manufacturing quality was analyzed. Then phased array ultrasonic testing (PAUT) technique was applied for crack detection for the three samples, and metallographic analysis was employed to verify detection results. The results showed that the increase of laser power can eliminate macro-cracks at the interface of the bimetallic sample, and micro-cracks at the interface can be detected by PAUT
An Expectation Maximization Based Adaptive Group Testing Method for Improving Efficiency and Sensitivity of Large-Scale Screening of COVID-19
No full textThe pathogen of the ongoing coronavirus disease 2019 (COVID-19) pandemic is a newly discovered virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Testing individuals for SARS-CoV-2 plays a critical role in containing COVID-19. For saving medical personnel and consumables, many countries are implementing group testing against SARS-CoV-2. However, existing group testing methods have the following limitations: (1) The group size is determined without theoretical analysis, and hence is usually not optimal. This adversely impacts the screening efficiency. (2) These methods neglect the fact that mixing samples together usually leads to substantial dilution of the SARS-CoV-2 virus, which seriously impacts the sensitivity of tests. In this paper, we aim to screen individuals infected with COVID-19 with as few tests as possible, under the premise that the sensitivity of tests is high enough. We propose an eXpectation Maximization based Adaptive Group Testing (XMAGT) method. The basic idea is to adaptively adjust its testing strategy between a group testing strategy and an individual testing strategy such that the expected number of samples identified by a single test is larger. During the screening process, the XMAGT method can estimate the ratio of positive samples. With this ratio, the XMAGT method can determine a group size under which the group testing strategy can achieve a maximal expected number of negative samples and the sensitivity of tests is higher than a user-specified threshold. Experimental results show that the XMAGT method outperforms existing methods in terms of both efficiency and sensitivity
Medical care oriented visual surveillance of patient falls in the hospital
No full text目的：提出一种面向医院患者的视觉监控跌倒检测算法，解决患者由于意外跌倒不能被及时发现的问题，为医护人员快速处理患者跌倒等异常行为提供必要的技术保障。方法：首先，基于深度神经网络模型检测监控图像中人体关节点（如肩部、肘部、腕部、胯部、膝关节等）在图像中的位置，再根据亲和度向量场模型提取人体骨架，最后计算患者躯干、腿部与地面的夹角作为判别性特征，判断监控区域内是否有患者出现意外跌倒。结果：实验结果表明，本文所提算法在实际的医院监护环境中的处理速度高达25帧/s，检测准确率高达96%。结论：该方法能够实时、准确地提取医院环境下患者的行为特征，并针对意外跌倒情况发出警报，为医护人员监测患者跌倒等异常行为提供更准确、方便的计算机辅助医疗护理方法。</p
Research on Contact Force Impedance Control Method of Blisk Grinding and Polishing Robot
No full text针对整体叶盘机器人自动化研磨抛光接触力控制的技术难点，对磨抛过程磨抛工具与叶片之间接触力进行分析，将负载静态标定与传感器零点在线补偿相结合，提出了基于零点漂移的机器人磨抛加工负载标定与补偿算法，并将其与基于位置的阻抗控制结合应用于整体叶盘的自动化磨抛加工。负载标定与补偿试验表明，加工过程中采用基本的标定与补偿算法的接触力和力矩的平均误差值从–0.12853N和0.0055N·m增加至–1.9826N和–0.1680N·m，而采用基于零点漂移的标定与补偿算法可将接触力和力矩的平均误差降低至–0.1532N和0.0083N·m，证明了该算法能够有效降低传感器零点漂移对接触力实现计算的影响。同时，力控试验表明，该算法与基于位置的阻抗控制结合能够有效实现对期望接触力的跟踪控制，从而明显提高整体叶盘磨抛加工的表面质量。</p
Robots at the Beijing 2022 Winter Olympics
No full textThe 2022 Winter Olympics has shown that robots can serve, protect, and help people excel in many aspects of their lives.</p
A Safe and Compliant Noncontact Interactive Approach for Wheeled Walking Aid Robot
No full textAiming at promptly and accurately detecting falls and drag-to gaits induced by asynchronous human-robot movement speed during assisted walking, a noncontact interactive approach with generality, compliance and safety is proposed in this paper, and is applied to a wheeled walking aid robot. Firstly, the structure and the functions of the wheeled walking aid robot, including gait rehabilitation robot (GRR) and walking aid robot (WAR) are illustrated, and the characteristic futures of falls and the drag-to gait are shown by experiments. To obtain gait information, a multichannel proximity sensor array is developed, and a two-dimensional gait information detection system is established by combining four proximity sensors groups which are installed in the robot chassis. Additionally, a node-iterative fuzzy Petri net algorithm for abnormal gait recognition is proposed by generating the network trigger mechanism using the fuzzy membership function. It integrates the walking intention direction vector by taking gait deviation, frequency, and torso angle as input parameters of the system. Finally, to improve the compliance of the robot during human-robot interaction, a PID_SC controller is designed by integrating the gait speed compensation, which enables the WAR to track human gait closely. Abnormal gait recognition and assisted walking experiments are carried out respectively. Experimental results show that the proposed algorithm can accurately identify abnormal gaits of different groups of users with different walking habits, and the recognition rate of abnormal gait reaches 91.2%. Results also show that the developed method can guarantee safety in human robot interaction because of user gate follow-up accuracy and compliant movements. The noncontact interactive approach can be applied to robots with similar structure for usage in walking assistance and gait rehabilitation
一种深海自适应液压钻机
No full text本发明公开了一种深海自适应液压钻机，涉及水下作业工具领域，解决了常见在进行钻孔动作时不可避免地会被海水冲击而发生偏移，进而导致出现钻孔的准确度存在较大偏差以及钻孔效率低下的问题，其技术方案要点是，主架体；转动机构，其具有固定端和转动端；螺旋机构，其与转动端同轴式传动连接；钻孔部，其与螺旋机构同轴式连接；螺旋机构的螺旋方向与钻孔部的螺旋方向相同，使螺旋机构能够产生与钻孔部钻孔方向相同的驱动力，本方案中的转动机构在驱动钻孔部转动的同时，其还能够为螺旋机构提供螺旋转动的动力，通过利用单个转动机构便能够同时提供钻孔部的钻孔动力以及前进推力，具有紧凑性高、钻孔稳定性高、可靠性高的特点