Game Development Reference
We won't repeat Dr. Jorgensen's development of the model here; instead, we'll show you
how to solve the resulting equations:
Those equations can be found in the Technical Appendix—Section 4 of Dr. Jorgensen's
book—but are listed here for convenience.
Table 19-3 explains what each symbol represents.
Table 19-3. Symbols used in golf swing model
Mass moment of inertia of the rod representing the arm. Units are kg-m 2 .
Mass moment of inertia of the rod representing the club. Units are kg-m 2 .
Mass of the club. Units are kg.
Length of the rod representing the arm. Units are m.
First moment of the rod representing the club about the wrist axis (where the club rod connects to the arm rod). Units
Angle swept by arm rod from initial backswing position. Units are radians.
Wrist-cock angle. Units are radians.
Acceleration due to gravity. Constant 9.8 m/s 2 .
Angle between arm rod and vertical axis. Units are radians.
Horizontal acceleration of the shoulder. Units are m/s 2 .
First moment of the arm rod about the shoulder axis. Units are kg-m.
Torque applied at the shoulder to the arm rod. Units are N-m.
Torque applied at the wrist joint to the club rod. Units are N-m.
These equations represent a coupled system of nonlinear differential equations. They
are coupled in that they both depend on the unknown quantities α and β. They are
clearly differential equations, as they both include time derivatives of the unknown