In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles（UAVs） in winds with constant speed and altitude is developed. Different to the widely considered line or orbit followin...In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles（UAVs） in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field（VF） strategy with the sliding mode control（SMC） method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm.展开更多
Adobe After Effects是一款在动画和影视后期制作方面不可或缺的软件,在特效制作方面有着优秀的表现,而且它还拥有大量的插件来丰富它的各种功能。After Effects表达式在视频制作中的使用,能避免一些烦琐无趣的工作,可以精确地控制各种...Adobe After Effects是一款在动画和影视后期制作方面不可或缺的软件,在特效制作方面有着优秀的表现,而且它还拥有大量的插件来丰富它的各种功能。After Effects表达式在视频制作中的使用,能避免一些烦琐无趣的工作,可以精确地控制各种属性,从而大幅提高工作效率。基于此,介绍After Effects表达式的语法、特点和优势,并把表达式应用在三维曲线路径建立方面,完成粒子在三维空间穿梭镜头的制作。展开更多
Ⅰ. INTRODUCTIONGreat attention has been paid in recent years to the investigations of dynamic growth of cracks in elastic solids under mixed mode loading conditions due to the practical importance. A crack usually pr...Ⅰ. INTRODUCTIONGreat attention has been paid in recent years to the investigations of dynamic growth of cracks in elastic solids under mixed mode loading conditions due to the practical importance. A crack usually propagates along a curved path under mixed mode loading. Freund and Clifton showed that the near-tip singular stress field for growing cracks has universal spatial dependence in a local Cartesian coordinate system(x, y)centered at the moving crack tip in such a way that the crack tip velocity vector is in展开更多
基金supported by the National Natural Science Foundation of China under Grant No.61403406
文摘In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles（UAVs） in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field（VF） strategy with the sliding mode control（SMC） method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm.
基金Project (50905041) supported by the National Natural Science Foundation of ChinaProject (20092302120079) supported by the Specialized Research Fund for the Doctroal Program of Higer Education, ChinaProject (09JD18) supported by Key Laboratory of Ministry Education for Conveyance and Equipment, East China Jiaotong University, China
文摘Adobe After Effects是一款在动画和影视后期制作方面不可或缺的软件,在特效制作方面有着优秀的表现,而且它还拥有大量的插件来丰富它的各种功能。After Effects表达式在视频制作中的使用,能避免一些烦琐无趣的工作,可以精确地控制各种属性,从而大幅提高工作效率。基于此,介绍After Effects表达式的语法、特点和优势,并把表达式应用在三维曲线路径建立方面,完成粒子在三维空间穿梭镜头的制作。
基金Project supported by the Engineering Geomechanics Laboratory, Institute of Geology, Academia Sinica
文摘Ⅰ. INTRODUCTIONGreat attention has been paid in recent years to the investigations of dynamic growth of cracks in elastic solids under mixed mode loading conditions due to the practical importance. A crack usually propagates along a curved path under mixed mode loading. Freund and Clifton showed that the near-tip singular stress field for growing cracks has universal spatial dependence in a local Cartesian coordinate system(x, y)centered at the moving crack tip in such a way that the crack tip velocity vector is in
