2017 年 83 巻 851 号 p. 17-00029
We aim to clarify dynamics of the wrist turn of the golf swing and the effect of the parameters on dynamic behavior at the wrist turn using the double pendulum model and the modal analysis method. Eigenvalue analysis was carried out and natural frequency and mode were calculated by using linearized equation of motion assuming the exterior angle of the cock angle is small. We found out that the first mode is a rigid mode and the second one is a vibration mode of the double pendulum, and the mode shapes are constant during the wrist turn even though natural frequency changes. By applying the modal analysis method we obtained equations of motion for the rigid mode and the vibration mode separately. Furthermore, using the theory of linear superposition, the equation of motion for the vibration mode was separated again into 3 equations which can help to understand the mechanism of the wrist turn. After accuracy of the proposed method for small exterior angle of the cock angle was confirmed by comparing with the exact solution using numerical integration, the proposed method was applied to the general case with large exterior angle of the cock angle which has nonlinearity, and the mechanism of the wrist turn and the effect of the parameters of the arm and wrist torque on the dynamic behavior at the wrist turn were clarified qualitatively. Finally parameter survey using the numerical integration for the original nonlinear equation of motion was carried out to show the validity of the proposed method.