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81.
Lin Cheng Zhenbo Wang Fanghua Jiang Junfeng Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):1114-1123
In this study, an adaptive neural network control approach is proposed to achieve accurate and robust control of nonlinear systems with unknown dynamics, wherein the neural network is innovatively used to learn the inverse problem of system dynamics with guaranteed convergence. This study focuses on the following three contributions. First, the considered system is transformed into a multi-integrator system using an input–output linearization technique, and an extended state observation technique is used to identify the transformed states. Second, an iterative control learning algorithm is proposed to achieve the neural network training, and stability analysis is given to prove that the network’s predictions converge to ideal control inputs with guaranteed convergence. Third, an adaptive neural network controller is developed by combining the trained network and a proportional-integral controller, and the long-standing challenge of model-based methods for control determination of unknown dynamics is resolved. Simulation results of a virtual control mission and an aerospace altitude tracking mission are provided to substantiate the effectiveness of the proposed techniques and illustrate the adaptability and robustness of the proposed controller. 相似文献
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以凌阳16位单片机SPCE061A为控制核心,通过所需运动轨迹曲线的参数方程建立运动控制模型,按照算法对两组驱动步进电机进行控制,实现了悬挂画笔在给定的范围内的定点运动、任意曲线运动以及圆心可任意设定的圆周运动等功能,不仅完成了要求发挥的部分功能,同时还增加了语音播放功能。 相似文献
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关于地球卫星运动中的坐标系附加摄动问题 总被引:1,自引:0,他引:1
关于卫星运动中的坐标系附加摄动,早期是从两种赤道坐标系中卫星轨道根数的差别采用大量球面三角公式的方法导出的,本文将改用与当今高精度数值解中的坐标转换关系,在岁差章动等参数完全一致的情况下,简要清晰地导出相应的坐标系附加摄动解,既容易被读者接受,又便于与对应的数值解进行比对。 相似文献
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本文对典型的迷宫式封严篦齿流场进行了观察与测量,以解释某些实验结果中的“反常现象”,即在台阶式篦齿封严结构中,泄漏系数会随间隙的增大而减小。在对10倍于原型的试件进行的水流模拟试验中,未观察到异常的旋涡结构,在泄漏量测量中也未发现类似的“反常”现象。此外,却意外发现在大间隙情况下,台阶直齿篦齿靠向一侧的封严方案比台阶式斜齿方案有更好的封严效果。 相似文献
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J. Park K.W. Min V.P. Kim H. Kil H.J. Kim J.J. Lee E. Lee S.J. Kim D.Y. Lee M. Hairston 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):650-654
The global distribution of low-latitude plasma blobs was investigated by in-situ plasma density measurements from the Korea Multi-Purpose Satellite-1 (KOMPSAT-1) and Defense Meteorological Satellite Program (DMSP) F15. In the observations, blobs occurred in the longitude sector where the activity of the equatorial plasma bubble (EPB) was appreciable, and additional blobs were found at the lower (KOMPSAT-1) altitude as in the EPBs. However, several notable differences exist between the distributions of EPBs and blobs. First, KOMPSAT-1 found few blobs around 0°E in March and June, as did DMSP F15 from 30°W to 120°E for every season. Second, the overall occurrences in December and March at the DMSP F15 (840 km) altitude were somewhat lower than expected from those of the EBPs. Third, at the DMSP F15 altitude, the occurrence probability of plasma blobs was less controlled by yearly variations in the solar activity. These results imply that topside ionospheric conditions as well as the existence of EPBs control further development of blobs. Additionally, it was found that the blob latitudes became higher as the yearly solar activity increased. Moreover, most of the blobs were encountered in the winter hemisphere, possibly due to the low ambient density. 相似文献
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This paper examines the way in which Earth observation is linked to UK science policy through the 1993 UK science White Paper and subsequent policy statements, and how the central theme of partnership has been developed in practice. An example of crop yield prediction is given to illustrate the strengths and the weaknesses of the approach. The UK science and space strategies are set in the context of the European Strategy for Space and links are made to the US global change research strategy. 相似文献
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