DETERMINATION OF THE FASTEST TRAJECTORIES OF MATERIAL POINT MOTION IN A HORIZONTAL VECTOR FIELD

Abstract

The article proposes a solution to the well-known Zermelo navigation problem by classical variational methods. The classical Zermelo problem within the framework of optimal control theory is formulated as follows. The ship must pass through the region of strong currents, the magnitude and direction of the current velocity are set as functions of phase variables. In this case, the relative speed of the ship is set, the module of which remains constant during movement. It is necessary to find such an optimal control that ensures the arrival of the ship at a given point in the minimum time, i.e. control of the ship by fast-action should be determined. In this paper, we consider the brachistochronic motion of a material point in a plane vector field of a mobile fluid, for which the classical variational problem of finding extreme trajectories is formulated. The aim of the study is to obtain equations of extreme trajectories along which a material point moves from a given starting point to a given finish point in the least amount of time. The solution to the problem was carried out using the classical methods of the theory of the calculus of variations. For a given variant of the boundary conditions, algebraic equations of extremals of motion of a material point were established in the form of segments of a power series. A comparative analysis of the fast-action was carried out both along extreme trajectories and along an alternative path — along a straight line that connects two given start and finish points. Analysis of the results showed that the considered variational problem has two solutions, which differ only in sign. However, only one solution provides the minimum time for moving a material point between two given points. It was also found that the extreme trajectory of the brachistochronic motion of a point is not straight, but has an oscillatory character.