According to Logvinovich cavity dependent expansion principle, a cavity developed by cavitator has memory effect, which arises cavity deformation at aft part of a supercavitating vehicle and leads time delay of travel state. This delay affects the dynamic behavior through changing hydrodynamic and moment on the control surface, and even induces instability. This paper focuses on the time delay effect of the underwater supercavitating vehicle, and a simplified dynamic model of underwater supercavitating vehicle with delay was established. First, a planing force was simplified in straight level state, then a simplified model of supercavitating vehicle with delay in longitude plane was obtained. Taking depth, pitch angle, vertical speed and pitch rate as state variant, [Formula: see text] state feedback controller was designed by linear matrix inequality (LMI) and Lyapunov stable theory was exploited to prove the asymptotic stability of the system. Simulation results show that, the controlled system is effectiveness for both simplified model and non-simplified model and it can track reference command signal.
Traditional 3D visual simulation of flexible fishing net has the problems of complicated computation and no collision detection studied. In this paper, a 3D visual simulation method is researched in order to simulate the dynamic deformation of the flexible fishing net. To solve the computational inefficiency of the traditional mass-spring model, a simplified mass-spring model is presented. At the same time, collision detection algorithm is employed in the simulation. The dynamic model of fishing net is described as the mass point set which are linked by massless springs. According to Newton`s classic theory, the kinetics model of the mass points are established. Explicit Euler method is adopted to solve the mathematical model of the fishing net. Realtime 3D visual dynamic simulations for the deformation of various kinds of fishing net are conducted and the results verify the rationality of the method presented in this paper.
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