Identification of Pitch Dynamics of An Autonomous Underwater Vehicle Using Sensor Fusion     

Abtahi  Seid Farhad  Alishahi  Mohammad Mehdi  Yazdi  Ehsan Azadi 《中国海洋工程》2019,33(5):563-572

This paper presents a method for identification of the hydrodynamic coefficients of the dive plane of an autonomous underwater vehicle. The proposed identification method uses the governing equations of motion to estimate the coefficients of the linear damping, added mass and inertia, cross flow drag and control. Parts of data required by the proposed identification method are not measured by the onboard instruments. Hence, an optimal fusion algorithm is devised which estimates the required data accurately with a high sampling rate. To excite the dive plane dynamics and obtain the required measurements, diving maneuvers should be performed. Hence, a reliable controller with satisfactory performance and stability is needed. A cascaded controller is designed based on the coefficients obtained using a semi-empirical method and its robustness to the uncertainties is verified by the μ-analysis method. The performance and accuracy of the identification and fusion algorithms are investigated through 6-DOF numerical simulations of a realistic autonomous underwater vehicle.  相似文献   

Problematic Soft Soil Improvement with Both Polypropylene Fiber and Polyvinyl Acetate Resin     

Esmaeil Masoumi  Seyed Mehdi Abtahi Forooshani  Farzad Abdi Nian 《Geotechnical and Geological Engineering》2013,31(1):143-149

Several methods are used to improve mechanical properties of loose soils including rewetting, soil replacement, compaction control, chemical additives, moisture control, thermal methods, and more recently, discrete fibers. All the methods are applied to soft soil to increase load bearing capacity and to improve other properties such as prevention of erosion and dust generation. In the present study, a new method of soil improvement using both discrete polypropylene (PP) fibers and polyvinyl acetate (PVAc) is introduced. The method is applied to improve load bearing capacity of a problematic sandy soil in both dry and saturated states. Based on the results from CBR tests on various specimens, it has been revealed that the combination of PP fiber and PVAc resin with weight percentages of 0.1 and 0.6 %, respectively, had the optimum effect in increasing the CBR value in both saturated and dry soil specimens. It should be mentioned that this method has caused a great increase in the CBR value in the saturated soil.  相似文献