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1.
Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the con-trol system's performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part's layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system. 相似文献
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《International Journal of Hydrogen Energy》2022,47(92):39239-39254
The energy management and trajectory tracking control are crucial to realize long-endurance autonomous flight for hybrid electric UAVs. This study aims to comprehensively consider energy management and trajectory tracking for hybrid electric fixed wing UAVs with photovoltaic panel/fuel cell/battery. A double-layer fuzzy adaptive nonlinear model predictive control method (DFNMPC) is proposed. Separated by the surplus demand power, energy management and trajectory tracking problem are decoupled into the high-layer fuzzy adaptive nonlinear model predictive controll problem (H-FNMPC) and low-layer fuzzy adaptive nonlinear model predictive controll problem (L-FNMPC). H-FNMPC solves the trajectory tracking and navigation control probelm for the greatest benefit of solar energy. L-FNMPC solves the power allocation problem of hybrid energy system for minimum equivalent hydrogen consumption. A fuzzy adaptive prediction horizon adjustment method based on UAV maneuvering degree is proposed to effectively improve proposed method adaptability to different mission profiles. Analogously, a fuzzy adaptive equivalent hydrogen consumption factor adjustment method in L-FNMPC is proposed to ensure the flexible utilization of battery. In addition, an equivalent hydrogen flow rate calculation method based on the real-time current ratio is proposed for PV/FC/Battery hybrid energy system. Numerical simulation results including a spiral trajectory tracking and a quadrilateral trajectory tracking, demonstrate that DFNMPC can simultaneously handle energy management and trajectory tracking problem for hybrid electric UAVs. Compared to hierarchical fuzzy state machine strategy, DFNMPC can save 13.3% hydrogen for the spiral trajectory tracking, and 56.9% for the quadrilateral trajectory tracking. It indicates that the energy efficiency can be improved from both levels of energy management and flight motion. The proposed method prospected for exploring high-energy-efficiency autonomous flight of hybrid electric UAVs in the future. 相似文献
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时间同步是多智能体网络协同工作的基础,具有重要意义。低成本无线传感器网络节点时钟易受到环境因素的影响,导致节点时间同步误差增大,网络信道负载增加。针对上述问题,提出了一种低时钟再同步周期、自适应温度补偿的无线传感器网络时间同步方法。首先,基于双向通信时间同步模型,提出了温度补偿的节点频移量动态估计模型;然后,采用Almon函数加权求和的方式对温度和频移量数据进行融合,解决数据采样率不匹配和模型维度高的问题;其次,为进一步提高时间同步精度,采用Kalman滤波器对频移量和相移量估计值进行滤波,并采用系统状态后验估计值对节点本地时间进行补偿;最后,参照IEEE 802.15.4标准对时间同步精度的要求,设计了一种失效风险最小化的再同步决策函数,最大限度提高节点再同步周期,减少信道负载。在高低温箱、室内和室外3种环境下进行实验以验证所提的方法。试验结果表明,与洪泛时钟同步协议(FTSP)时间同步协议相比,自适应温度补偿的时间同步(ATCTS)算法平均时间同步误差降低了97.4%,室外环境下平均时间同步周期为324 min。 相似文献
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通过研究润滑油糠醛精制装置抽出液回收系统二、三效蒸发塔压控调整对装置能耗的影响发现,三效蒸发塔进行憋压操作对装置能耗降低是有利的,二效蒸发塔在憋压时极易降低醛气的蒸发量,并且对能耗的影响也不大,最终得出装置较优的操作参数,既解决了糠醛干燥塔液面受外界影响波动较大的问题也降低了装置能耗。 相似文献
8.
高管团队决策绩效是提高企业创新能力、把握发展机遇、获得持续竞争力的关键因素之一。通过对调味品上市企业2016-2018年财务年报的具体分析,基于描述性统计分析与分步多元线性回归分析的方法,探讨了高管团队异质性、沟通频率以及决策绩效之间的互动机理。结果表明,高管团队男性比例、专业、职业背景异质性与沟通频率呈正相关,年龄、任期异质性与沟通频率呈负相关,沟通频率正向调节高管团队异质性与决策绩效的关系,并进一步增强高管团队异质性效能。研究结果对目前激烈竞争环境下调味品企业组建高管团队及优化管理沟通具有启示意义。 相似文献
9.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
10.
单轨车辆的走行部径向通过曲线时可以减小走行轮的磨耗和导向轮的载荷。以跨坐式单轨车辆辅助导向装置的几何关系和油气弹簧的力学特性为出发点,推导辅助导向装置产生力矩与转向架和车体之间摇头角度的解析关系。建立有辅助导向装置时车辆稳态曲线通过的力学模型,分析辅助导向装置能够使转向架在圆曲线上处于径向位置的条件,并利用多刚体动力学软件建立跨坐式单轨车辆的稳态曲线通过验证模型。通过理论分析和模型仿真计算发现,当合理油压弹簧预压力选择合适的数值时,辅助导向装置的输出力矩与二系悬挂的回转力矩相互抵消,走行部的摇头角接近零,能够使转向架在圆曲线上处于径向位置,并有效缓解走行轮与导向轮的磨耗。 相似文献