Research On Optimal Control Of The Seamless Table Tennis

The sport of table tennis has been experiencing many revolutions since its origin. New trends accompanied with the changing of the competition rules, e.g. the spreading of no-hiding service, the changing of the ball size, and the replacement of the21-points system by the11-points system, are the upgrade of the equipment and the enhancement of the ball-controlling skills. Each change inevitably influences the development of table tennis, and attracts more players to devote their passion and time into this amazing sport.Recently, another rule-changing proposal will be initiated after the London Olympic Games, i.e., the40mm ball made by celluloid with a slit on the surface will be replaced by a seamless ball made by a new material. Since celluloid is poisonous and will be harmful after long-term exposure, the aim of this proposal is to eliminate the harm of the celluloid to players. According to the past experiences of the other changes, this change will affect many aspects of this sport, such as the mainstreams of the playing skills, the feel of hitting the ball, the suitability of equipment, and so on. Therefore, it is highly demanded to study the characteristics of the new seamless ball. Resolutions will be the key in training and competing with the new ball.As a professional table tennis athlete who has ample experiences of training and competing, the author investigates the kinetic characteristics of the new ball and compares the results with the current ball. The results of this analysis are explicit and practical.(1) A numerical model is established on the movement of the table tennis ball by using the rigid body dynamics. The equation is solved by the fixed initial value and the fixed boundary value. The ideal elastic collisions are assumed for the ball rebound on the table. By solving the equation, the ball trajectory is obtained, along with the ball’s over-net time and the finishing-down time. Then, the quantitative relation of the initial centroid speed and the angular spin rate with the bat’s swing speed is considered in the initial conditions. The ball pass over the net obstacle is applied as the constraint.(2) The comparison results show that by drawing a loop ball the athletes can maximize the bat’s swing speed limit, while producing an arc trajectory to improve the hit rate. The kinetic energy of the third step-down is even greater than the initial speed, and hence harder for the rival to defense. Therefore, the loop ball skills will still be the mainstream technology after the implementation of the seamless ball.(3) Almost all players can distinguish the new and the current ball by the hitting sound. Mechanically, the new ball has better elasticity, stronger hardness and smaller elastic deformation.(4) The rotation of the new ball is smaller than the one with slit when they are experiencing the same friction force. The comprehensive ball hitting feels are quite different. Players have to spend time to adapt this difference.(5) From the ball producers’perspective, producing the new ball needs simpler process, therefore can reduce the cost, raise the production rate and protect the environment. The material of the new ball, called the polyester fiber, is non-flammable which can largely reduce the transportation cost and raise the safety factor. Most importantly, the polyester fiber is a non-poisonous material and will be safe to players.