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Design and Motion Performance Analysis of Turbulent AUV Measuring Platform
No full textThe use of a multi-functional autonomous underwater vehicle (AUV) as a platform for mak-ing turbulence measurements in the ocean is developed. The layout optimization of the turbulence package and platform motion performance are limitation problems in turbulent AUV design. In this study, the computational fluid dynamics (CFD) method has been used to determine the optimized layout position and distance of the shear probe integrated into an AUV. When placed 0.8 D ahead of the AUV nose along the axis, the shear probe is not influenced by flow distortion and can contact the water body first. To analyze the motion of the turbulence AUV, the dynamic model of turbulence AUV for planar flight is obtained. Then, the mathematical equations of speed and angle of attack under steady-state motion have also been obtained. By calculating the hydrodynamic coefficients of the turbulence AUV and given system parameters, the simulation analysis has been conducted. The simulation results demonstrated that the speed of turbulent AUV is 0.5–1 m/s, and the maximum angle of attack is less than 6.5◦, which meets the observation requirements of the shear probe. In addition, turbulence AUV conducted a series of sea-trials in the northern South China Sea to illustrate the validity of the design and measurement. Two continuous profiles (1000 m) with a horizontal distance of 10 km were completed, and numerous high-quality spatiotemporal turbulence data were obtained. These profiles demonstrate the superior flight performance of turbulence AUV. Analysis shows that the measured data are of high quality, with the shear spectra being in very good agreement with the Nasmyth spectrum. Dissipation rates are consistent with background shear. When shear velocity is weak, the measurement of dissipation rate is 10−10 W Kg−1. All indications are that the turbulence AUV is suitable for long-term, contiguous ocean microstructure measurements, which will provide data needed to understand the temporal and spatial variability of the turbulent processes in the oceans.</p
Study on Power Consumption and Stealing Law of Large-Scale Low Voltage Power Supply Area
No full text针对国内外在220 V和380 V供电电压的低压地区电力消耗的研究较少,很难探究实时线损的问题。对供电、用电、线损、窃电4个方面进行数据分析,建立统计模型与聚类模型,探索电力消费和窃电的规律。利用时间序列分析、频谱分析、概率密度函数、互补累积分布函数的统计模型进行分析。结果表明窃电用户用电周期是正常用户的2倍,窃电用户的日均用电量大于正常用户,窃电用户在台区线损率大于40%时数量激增,线损率到达65%时数量放缓,可以优先排查此区间的台区。基于时间序列相似度度量和k-means聚类相结合的聚类模型,将566个台区365维的时间序列聚类得到6类不同的台区线损率模式,并通过核密度估计对比了他们的分布差别,可以帮助快速排查出重点窃电台区并监测线损率改善的情况。</p
System Error Calibration in Large Datasets of Wireless Channel Sounding for Industrial Applications
No full textChannel impulse response (CIR) datasets, which represent the characteristics of wireless channels, play a vital role in industrial applications. Unfortunately, systematic errors have been discovered within CIR datasets. These errors have undesirable effects in wireless localization, physical layer security, and related applications. In addition, existing CIR calibration methods do not consider applicability to industrial scenarios. To address this concern, two channel sounder error calibration (CSEC) methods are proposed. The first CSEC method based on phase compensation (CSEC-Phase) extracts the direct path signal to estimate errors to avoid interference from rich multipath signals for stationary measurements in complex industrial environments. Moreover, to solve the problem of the inability to estimate the CIR error in mobile measurements due to the rapid dynamic change of the channel, a second CSEC method based on carrier frequency recovery (CSEC-Frequency) is proposed that extracts the frequency offset of the system clock to compensate for systematic error utilizing the stability of clock drift. Furthermore, the L1-norm distance metric is employed to measure the differences between CIRs and evaluate the calibration performance. Our results reveal that the proposed CSEC methods are effective on diverse CIR datasets measured by different11The MATLAB code of the CSEC methods has been shared on GitHub: https://github.com/QiWang-GH/Industrial-Wireless-Channel-Sounding-Error-Calibration-IW-CSEC. equipment in different scenarios.</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
Characterization of interconnectivity of gelatin methacrylate hydrogels using photoacoustic imaging
No full textHydrogels can provide a three-dimensional microenvironment for cells and thus serve as an extracellular matrix in a biofabrication process. The properties of hydrogels, such as their porosity and mechanical properties, significantly influence the cell growth. However, there is still a lack of effective methods for characterizing the hydrogel structure noninvasively. Herein, a photoacoustic (PA) imaging-based method is proposed for the characterization of gelatin methacrylate (GelMA) hydrogels. Owing to their high PA contrast, red blood cells (RBCs) are included as mediators in the GelMA hydrogel to analyze its pore distribution. The interconnectivity of the pores is further analyzed through the lysis of RBCs. The diffusion of the RBC lysis buffer in the GelMA is consistent with the trend observed in simulations. The analyzed vitality of HEK293 cells in different GelMA hydrogels reveals that understanding the diffusion of solutes (i.e., nutrients) is a potential strategy to optimize the hydrogel parameters during biofabrication
A humanoid robotic hand capable of internal assembly and measurement in spacesuit gloves
No full textPurpose To identify the dexterity of spacesuit gloves, they need to undergo bending tests in the development process. The ideal way is to place a humanoid robotic hand into the spacesuit glove, mimicking the motions of a human hand and measuring the bending angle/force of the spacesuit glove. However, traditional robotic hands are too large to enter the narrow inner space of the spacesuit glove and perform measurements. This paper aims to design a humanoid robot hand that can wear spacesuit gloves and perform measurements. Design/methodology/approach The proposed humanoid robotic hand is composed of five modular fingers and a parallel wrist driven by electrical linear motors. The fingers and wrist can be delivered into the spacesuit glove separately and then assembled inside. A mathematical model of the robotic hand is formulated by using the geometric constraints and principle of virtual work to analyze the kinematics and statics of the robotic hand. This model allows for estimating the bending angle and output force/torque of the robotic hand through the displacement and force of the linear motors. Findings A prototype of the robotic hand, as well as its testing benches, was constructed to validate the presented methods. The experimental results show that the whole robotic hand can be transported to and assembled in a spacesuit glove to measure the motion characteristics of the glove. Originality/value The proposed humanoid robotic hand provides a new method for wearing and measuring the spacesuit glove. It can also be used to other gloves for special protective suits that have highly restricted internal space.</p
Design and Motion Performance Analysis of Turbulent AUV Measuring Platform
No full textThe use of a multi-functional autonomous underwater vehicle (AUV) as a platform for making turbulence measurements in the ocean is developed. The layout optimization of the turbulence package and platform motion performance are limitation problems in turbulent AUV design. In this study, the computational fluid dynamics (CFD) method has been used to determine the optimized layout position and distance of the shear probe integrated into an AUV. When placed 0.8 D ahead of the AUV nose along the axis, the shear probe is not influenced by flow distortion and can contact the water body first. To analyze the motion of the turbulence AUV, the dynamic model of turbulence AUV for planar flight is obtained. Then, the mathematical equations of speed and angle of attack under steady-state motion have also been obtained. By calculating the hydrodynamic coefficients of the turbulence AUV and given system parameters, the simulation analysis has been conducted. The simulation results demonstrated that the speed of turbulent AUV is 0.5-1 m/s, and the maximum angle of attack is less than 6.5 degrees, which meets the observation requirements of the shear probe. In addition, turbulence AUV conducted a series of sea-trials in the northern South China Sea to illustrate the validity of the design and measurement. Two continuous profiles (1000 m) with a horizontal distance of 10 km were completed, and numerous high-quality spatiotemporal turbulence data were obtained. These profiles demonstrate the superior flight performance of turbulence AUV. Analysis shows that the measured data are of high quality, with the shear spectra being in very good agreement with the Nasmyth spectrum. Dissipation rates are consistent with background shear. When shear velocity is weak, the measurement of dissipation rate is 10(-10) W Kg(-1). All indications are that the turbulence AUV is suitable for long-term, contiguous ocean microstructure measurements, which will provide data needed to understand the temporal and spatial variability of the turbulent processes in the oceans
一种正交双关节式电推力器指向机构
No full text本发明涉及航天器中电推力器调节推力方向的机构，特别涉及一种正交双关节式电推力器指向机构。该机构包括旋转执行器Ⅰ、万向节环、电推力器、上旋转架、下固定架及旋转执行器Ⅱ，其中万向节环饶Y轴转动地安装在下固定架上，旋转执行器Ⅱ设置于下固定架上，且旋转执行器Ⅱ的输出端与万向节环连接，旋转执行器Ⅱ用于驱动万向节环饶Y轴转动；上旋转架绕X轴转动地与万向节环连接，旋转执行器Ⅰ设置于上旋转架上，且旋转执行器Ⅰ的输出端与万向节环连接，旋转执行器Ⅰ用于驱动上旋转架绕X轴转动；电推力器设置于上旋转架上。本发明通过使用一个万向节环达到调节上支架转动的目的，可以实现机构的上旋转架在行程范围内任意方位的指向
一种面向铝合金激光增材修复的成形质量控制方法
No full text本发明公开了一种面向铝合金激光增材修复的成形质量控制方法，属于铝合金修复的成形控制技术领域。在激光修复过程中，通过循环水冷却系统控制成形，冷却系统由不锈钢循环水冷却板、K型热电偶、零件夹具、温度监控仪和水冷机等关键部件构成。该冷却系统可以通过对基板温度的实时监控，使基板温度均匀降低。通过设置正确的循环水冷却温度与冷却时间，使修复过程中的热积累有效减少，从而细化组织，减少孔隙率，提高合金性能，改善成形质量。该冷却方法及冷却装置在铝合金基材冷却方面有具有很大的应用前景
一种多自由度拇指辅助的软体康复外骨骼机器人
No full text本实用新型涉及医用康复训练和助力设备，具体地说是一种多自由度拇指辅助的软体康复外骨骼机器人，包括软体外骨骼手套、肌腱拉力线、柔性连杆、驱动装置及控制系统，肌腱拉力线一端连接直线驱动器，另一端连接软体外骨骼手套用以驱动拇指的外展/内收和弯曲/伸展两个自由度；柔性连杆一端与拇指指套铰接，另一端与手背结构件铰接，并通过肌腱拉力线的收缩沿着滑动槽移动，从而驱动拇指的内收和外展运动；肌腱拉力线连接拇指背侧驱动拇指的伸展运动，另一根拉力线连接拇指掌侧驱动拇指的弯曲运动。本实用新型可以有效地助力中风患者的拇指运动，以完成所需的训练任务，尺寸小、重量轻、具有非常好的可穿戴性，便于手功能障碍的患者在日常生活中实用