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601.
This article presents a novel electrical/mechanical hybrid 4-redundancy brushless DC torque motor (BLDCM), which has found applications in direct drive actuators (DDA) of aerial vehicles. This motor is characteristic of electrical/mechanical hybrid 4-redundancy by securing two stators along with two rotors on the same shaft. Each stator contains two sets of windings embedded in separated slots. Furthermore, compared to the scheme of two electrical dual-redundancy BLDCMs linked by a mechanical transmission, the proposed motor has lower volume and lighter weight, eliminates the nonlinearity caused by the gap of the mechanical transmission, moderates the requirement for the torque balance between redundancies and reduces the cogging torque by shifting the magnets. Both magnetic circuit calculation and the finite element analysis (FEA) of the electromagnetic field are conducted to optimize the design process. A prototype motor has been produced and tested. The results indicate that its performances comply with the requirements presented by designers. Moreover, the position frequency response of the prototype in the DDA's unloaded situation has also demonstrated the fulfillment of desired dynamic characteristics. 相似文献
602.
为提高复杂电磁环境中辐射源信号的生成效率和逼真度,提出了一种基于仿真软件驱动实际信号生成的辐射源信号产生方法.首先,通过M atlab仿真计算得到任意辐射源信号(以辐射源信号中的LFM信号为例);其次,利用LabVIEW设计出相应的I/Q信号读取及发射单元;最后,经任意波形信号发生器生成射频信号.试验表明,利用计算机软件仿真出的辐射源信号与实际生成的射频信号相一致,该方法为实现快速仿真生成任意辐射源信号及其可视化研究提供了技术支持,独立的读取单元减少了系统内存的占用,具有一定的工程实践意义. 相似文献
603.
C. Zeitlin D. M. Hassler R. F. Wimmer-Schweingruber B. Ehresmann J. Appel T. Berger E. Böhm S. Böttcher D. E. Brinza S. Burmeister J. Guo J. Köhler H. Lohf C. Martin D. Matthiä A. Posner S. Rafkin G. Reitz Y. D. Tyler M. Vincent G. Weigle Y. Iwata H. Kitamura T. Murakami 《Space Science Reviews》2016,201(1-4):201-233
604.
Zhinmin Liu Yangyang Li Fei Li Jinyun Guo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(6):1435-1443
Ionosphere delay is very important to GNSS observations, since it is one of the main error sources which have to be mitigated even eliminated in order to determine reliable and precise positions. The ionosphere is a dispersive medium to radio signal, so the value of the group delay or phase advance of GNSS radio signal depends on the signal frequency. Ground-based GNSS stations have been used for ionosphere monitoring and modeling for a long time. In this paper we will introduce a novel approach suitable for single-receiver operation based on the precise point positioning (PPP) technique. One of the main characteristic is that only carrier-phase observations are used to avoid particular effects of pseudorange observations. The technique consists of introducing ionosphere ambiguity parameters obtained from PPP filter into the geometry-free combination of observations to estimate ionospheric delays. Observational data from stations that are capable of tracking the GPS/BDS/GALILEO from the International GNSS Service (IGS) Multi-GNSS Experiments (MGEX) network are processed. For the purpose of performance validation, ionospheric delays series derived from the novel approach are compared with the global ionospheric map (GIM) from Ionospheric Associate Analysis Centers (IAACs). The results are encouraging and offer potential solutions to the near real-time ionosphere monitoring. 相似文献
605.
607.
高精度寻北是旋转调制光纤陀螺惯导实现高精度导航的前提,也是其技术优势的体现。针对当前旋转调制光纤陀螺惯导在快速高精度寻北中遇到的问题,对其寻北精度极限进行了深入研究,梳理出4项最主要的影响因素,对其影响机理、误差模型、量级进行了深入的分析,并通过样机试验进行了验证。结果表明,尽管随机游走系数是制约寻北精度极限的最终因素,但陀螺刻度系数误差、扰动速度、航向效应等误差处理不好,将严重影响旋转调制寻北精度;通过采取措施,高精度光纤陀螺旋转调制惯导5min寻北精度已达到35″(3σ),进一步提高精度的措施正在研究中。 相似文献
608.
In this paper, a novel transmission protocol based on polar coding is proposed for the half-duplex degraded relay channel. In the proposed protocol, referred to as the partial message relaying, the relay only needs to forward a part of the decoded source message that the destination needs according to the exquisite nested structure of polar codes. Theoretically, it is proved that the scheme can achieve the capacity of the half-duplex relay channel under the decode-and-forward (DF) cooperation strategy while enjoying low encoding/decoding complexity. Practically, in order to minimize the global transmission power, the optimization of the power allocation is performed between the source and the relay by using information theoretic tools. Furthermore, a joint iterative soft parallel interference cancellation receiver structure is developed to suit to the proposed scheme. Simulation results show that the proposed scheme outperforms the conventional scheme designed by low-density parity-check (LDPC) codes. 相似文献
609.
Based on the uncertainty theory, this paper is devoted to the redundancy allocation problem in repairable parallel-series systems with uncertain factors, where the failure rate, repair rate and other relative coefficients involved are considered as uncertain variables. The availability of the system and the corresponding designing cost are considered as two optimization objectives. A crisp multiobjective optimization formulation is presented on the basis of uncertainty theory to solve this resultant problem. For solving this problem efficiently, a new multiobjective artificial bee colony algorithm is proposed to search the Pareto efficient set, which introduces rank value and crowding distance in the greedy selection strategy, applies fast non-dominated sort procedure in the exploitation search and inserts tournament selection in the onlooker bee phase. It shows that the proposed algorithm outperforms NSGA-II greatly and can solve multiobjective redundancy allocation problem efficiently. Finally, a numerical example is provided to illustrate this approach. 相似文献
610.