2401 A Study on the initial condition of the screw kick in rugby
Details
The objective of this study is to reveal the initial condition of the optimal screw kick in rugby as well as the feature of that. A kick reaching touch safely gives a psychological boost to a team by relieving a period of pressure by the opposition. The objective here is to kick into touch safely, as well as to achieve maximum distance in the forward direction. Since there are two objective functions, this represents a multi-optimization problem. The optimization was carried out by using an elitist non-dominated sorting genetic algorithm. Distance achieved in flight is considered as an objective function, as well as the lateral deviation between the ball and the touchline. Six initial conditions ; these are the magnitude of the velocity vector, the flight path angle, the azimuth angle, the spin rate, the pitch angle and the yaw angle, were defined as control parameters. The results are summarized as follows: it is impossible for both objective functions to be satisfied simultaneously, although the largest value of distance achieved in flight and the smallest value of the lateral deviation between the ball and the touchline is the ideal situation. This kind of conflicting solution is called a "Pareto-optimal solution". The optimal kick in Pareto-optimal solutions made by the leg nearest the touchline produces a greater flight distance than the optimal kick in Pareto-optimal solutions made using the leg furthest from the touchline. The initial pitch angle, which is the angle between the longitudinal axis of the ball and the horizontal plane, should be comparable to or slightly greater than the initial flight path angle in order to satisfy the Pareto-optimal solutions.
