中文说明：变步长龙格库塔法，用于解决四阶微分方程组求解析解的问题，尤其适用于两自由度间隙碰撞问题的解决。
English Description：
The variable step Runge Kutta method is used to solve the problem of solving the fourth-order differential equations, especially for the two degree of freedom gap collision problem.