Robust sliding mode control of a mini unmanned underwater vehicle equipped with a new arrangement of water jet propulsions: Simulation and experimental study     

《Applied Ocean Research》2016

This paper presents dynamical modeling and robust control of a Mini Unmanned Underwater Vehicle (MUUV) equipped with a new arrangement of water jet propulsion. The water jet propulsion includes some advantages comparing with a propeller one, such as, reducing the number of required motors, desired number and arrangement of the propulsions, removing adverse torque and cavitation due to propeller rotation and etc. In order to model the proposed MUUV, the gray box method is used in such a way that the dynamical equation of motion is derived analytically by Euler-Lagrangian method, and then the hydrodynamic coefficients (such as added mass and drag coefficients) are derived by performing some tests in a Computational Fluid Dynamic (CFD) software. The dynamical model is used to simulate the MUUV system and also to design the proposed controllers, which are Feedback Linearization Controller (FLC) and Sliding Mode Controller (SMC). In order to investigate and compare the performance of the MUUV and the applied controllers, three types of tests including a desired signal tracking case and two desired path tracking cases are designed. To do so, a method is presented to obtain the desired signals from a desired path under predetermined conditions. Then, an MUUV prototype is designed and constructed in order to investigate the performance of the proposed water jet propulsions and controllers for regulation and tracking desired signal purpose, experimentally. As it is expected, the simulation and experimental results show better performance of the SMC compared to FLC. Furthermore, the experimental results reveal that the water jet propulsion is implementable to practical prototypes and also can be produced in an industrial level.  相似文献   

The most sensitive initial error modes modulating intensities of CP- and EP- El Niño events     

《Dynamics of Atmospheres and Oceans》2021

The two types of El Niño events simulated by the Geophysical Fluid Dynamics Laboratory Climate Model version 2p1 (GFDL CM2p1) model and its “spring predictability barrier” (SPB) associations are examined. By conducting the ensemble hindcast experiments related to the sea temperature on the whole Pacific, both of the predictions for CP- and EP-El Niño show a significant SPB phenomenon, but the CP-El Niño features a much weaker SPB compared to the EP-El Niño. Further analyses revealed that, for CP-El Niño events, the initial sea temperature errors of the North Pacific with triple-like shape, referred to as negative Victoria Mode (VM) induces the largest prediction errors in Niño4 areas and modulates the intensities of CP-El Niño events. While for EP-El Niño events, the initial sea temperature errors in the subsurface layer of the western equatorial Pacific and the upper layer of the Southeast Pacific (15–30ºS) with the meridional mode induce the largest prediction errors in Niño3 areas and modulates the intensities of EP-El Niño events. Obviously, results stress that, in order to reduce final prediction errors and obtain better predictions in terms of intensity on the two types of El Niño events, we should mainly focus on initial sea temperature accuracy in not only the subsurface layer of the west equatorial Pacific but also the surface layer of southeast Pacific and the region covered by the VM-like mode in the North Pacific.  相似文献   

一种利用加窗LSSVM拟合GPS在轨卫星钟差的算法     

张清华  隋立芬  王冰  甘雨 《武汉大学学报(信息科学版)》2012,37(9):1032-1035

利用最小二乘支持向量机(least squares support vector machine,LSSVM)来对GPS在轨卫星钟差数据进行拟合,针对LSSVM拟合钟差两端发散的现象,利用加窗的方法进行抑制。采用IGS提供的精密钟差进行算例分析,发现加窗LSSVM钟差拟合算法比现有的钟差拟合算法精度更高,且基于多项式的核函数比较适合加窗LSSVM钟差拟合。  相似文献   

结合影响分析的抗隐差型Bayes粗差探测方法     

王延停  归庆明 《武汉大学学报(信息科学版)》2012,37(9):1055-1058

通过分析隐差现象产生的原因,将基于观测误差的后验概率法与基于Kullback-Leiber距离的影响分析相结合,并利用逐个搜索法的思想,给出了一种粗差探测的抗隐差型Bayes方法。实验结果表明,采用该方法进行粗差探测切实可行,不但有效地发现了被掩盖的粗差,而且运算简单,效率较高。  相似文献   

基于Z-I关系和变分校正法改进雷达估测降水   总被引：5，自引：2，他引：3  

马慧  万齐林  陈子通  林振敏  陈桢华  吴嘉豪 《热带气象学报》2008,24(5):546-549

将新回归系数估计法和新误差订正法应用于3 km的雷达CAPPI估测降水,首先用新的回归方法得出更合理的Z-I关系;再用基于变分技术的新的误差订正方法对估算出的降水进行订正,获得较好的估算结果,并且用2005年6月17～25日广东自动站降水和每6分钟一次的雷达基数据对新回归系数估计法和新误差订正法进行验证,结果表明:将新回归系数估计法和新误差订正法用于雷达估测降水,能更好地对雷达回波强度估算降水的一些常见误差进行校订.  相似文献   

中国历史探空资料中的一些过失误差及偏差问题   总被引：43，自引：4，他引：43  

翟盘茂 《气象学报》1997,55(5):563-572

利用综合静力学质量控制技术，分析中国历史探空资料集中的一些过失误差情况；着重研究了１９６０年代探空仪器变化给温度和湿度时间序列带来的不均一性问题；进一步讨论了中国近期探空温度和湿度资料中垂直层次上存在的一些偏差问题  相似文献   

The accuracy of GOES satellite clocks     

K. R. Peal 《Marine Geophysical Researches》1991,13(4):349-352

Clocks that receive and decode time signals from the GOES satellites are commonly used to provide accurate time reference for the recording of a wide variety of data types in academic research. These satellite clocks must be used with adequate knowledge of their operation. When corrections for satellite position are not made, comparison data presented in this paper show that errors of up to several milliseconds will result. However, with care and the application of proper corrections it is shown that accuracies of 100 to 200 microseconds are achievable.  相似文献   

数字地质剖面的误差计算校正方法探讨          下载免费PDF全文

周国库  张建辉 《甘肃地质》2007,16(4):93-96,46

随着地质矿产勘查和综合研究数字化进一步推广应用,地质剖面的误差校正越显重要。对实测数字化地质剖面,可借助控制点的坐标,利用测量有关知识,通过计算,平差误差,重新计算出校正后的导线三参数iφ′、iβ′、L0i′,重新入库投影,从而把测量点准确地校正到控制点上,达到剖面误差校正的目的。  相似文献   

PREDICTION OF THE GRAIN SIZE OF SUSPENDED SEDIMENT： IMPLICATIONS FOR CALCULATING SUSPENDED SEDIMENT CONCENTRATIONS USING SINGLE FREQUENCY ACOUSTIC BACKSCATTER     

R. A. KUHNLE D. G. WREN J. P. CHAMBERS 《国际泥沙研究》2007,22(1):1-15

Collection of samples of suspended sediment transported by streams and rivers is difficult and expensive. Emerging technologies, such as acoustic backscatter, have promise to decrease costs and allow more thorough sampling of transported sediment in streams and rivers. Acoustic backscatter information may be used to calculate the concentration of suspended sand-sized sediment given the vertical distribution of sediment size. Therefore, procedures to accurately compute suspended sediment size distributions from easily obtained river data are badly needed. In this study, techniques to predict the size of suspended sand are examined and their application to measuring concentrations using acoustic backscatter data are explored. Three methods to predict the size of sediment in suspension using bed sediment, flow criteria, and a modified form of the Rouse equation yielded mean suspended sediment sizes that differed from means of measured data by 7 to 50 percent. When one sample near the bed was used as a reference, mean error was reduced to about 5 percent. These errors in size determination translate into errors of 7 to 156 percent in the prediction of sediment concentration using backscatter data from 1 MHz single frequency acoustics.  相似文献   

六自由度地震动测量方法及其误差分析     

杨振宇  卢海燕  蔡莉  钟慧 《世界地震工程》2007,23(4):84-87

根据无陀螺捷联惯导原理，提出一种用八支力平衡加速度计测量六自由度地震动的方法，并对该测量方法的误差进行了分析。  相似文献