Bounceless Collision

Touch, an ability so fundamental that it has been taken for granted by humans, is difficult for robots; robot fingers bounce off objects they try to touch or grasp, similar to a ball bounces off a racket. Touch requires a sudden change of force. A new term "jumpulse" is introduced to represent the new concept of a sudden change of force, as impulse denotes a sudden change of momentum. Jumpulse is also responsible for ball control, the ability of a player to keep a moving ball in contact with a racket for a prolonged time-the secret of consistency in sports.

Ball control involves a great deal of precision. To keep the ball on the racket for a prolonged period of time can be achieved by increasing the acceleration of the racket within a very short period of time at a precise moment near the maximum indentation. The problem involves thinking motion in an accelerating frame and is explained below.

The ball initially moves in the direction of the racket, and the racket is moving toward the ball with a constant velocity. The ball and the racket come into contact at time=0. The racket is indented by the moving ball and reaches the maximum indentation at time=2 milliseconds (msec). Ordinarily, the ball would bounce out of the racket from time=3 msec to time=5 msec.

When the racket is at its maximum indentation at time=2 msec, there is a spring force exerting on the ball trying to push the ball out of the racket. As the result of the spring force, the ball will accelerate away from the racket with an acceleration proportional to the spring force. Initially, the collision phenomenon can be described as a simple collision between a moving ball with a moving racket. The racket slows down as a result of the collision. If at the precise time=2 msec an additional force is suddenly applied to the racket, the racket will start to accelerate at an acceleration proportional to the applied force. If the acceleration of the racket is equal to the acceleration of the ball, as soon as the ball is being accelerated out the racket, the racket will accelerate to catch up with the ball. Applying the needed acceleration on the racket to catch up with the accelerating ball will cause the relative spatial positions of the ball and the racket to remain the same, that is that they will be in contact with each other.

Another way of viewing the phenomenon of prolonged contact is to appeal to the plausible physical reasoning that two objects initially in contact with each other and moving with the same acceleration will remain in contact. The strange part of the phenomenon of prolonged contact is that the acceleration of one of the two objects, namely, the ball is produced by the other object, namely, the racket.

The phenomenon could ignite an industrial revolution involving general purpose robots. The mechanism of touch will allow the construction of bounceless automobiles, airplanes during landing, and spacecraft while docking. The understanding of ball control will help in the designing of sports equipment, including shoes and gloves, based on scientific principles.

Thanks and please feel free to contact us !

Home Page