Usual human gait can be modeled as continual impact phenomenon that happens due to the topological change of the kinematic structure of the two feet. Human-being adapts his own control algorithm to minimize the ill-effect due to the collision with the environment. In order to operate a Humanoid robot like the Human-being, it is necessary to understand the physics of the impact and to derive an analytical model of the impact. In this paper, specially, we focus on impact analysis of the kicking motion in playing soccer. At the instant of impact, the external impulse exerted on the ball as well as the internal impulse experienced at the joints of the human-body are important properties in human body. Initially, we introduce the complete impulse models of lower-extremity model and analyze the impulses for several kicking postures of the lower-extremity. Secondly, a trajectory planning algorithm of a ball, in which the initial velocity of the ball is calculated for a desired trajectory of the ball, will be introduced. Aerodynamic effect such as drag force and lift force is also considered. We carry out numerical simulation to verify the effectiveness of the proposed analytical methodology.
