m]3+[413+区kx2=-mF() 设{x(t)}=∑{X}D() 代入运动方程,得 m∑{X}D()+∑{D()+]∑{XD()=[m(2() 方程两端左乘{Xy XH[mk∑{X)B()+{Xye∑{X,D()+ +{XH[k]∑{XD()=-{XHm(2() LrYImlX,D(t+[) D(t+(kkR, D,(t) Xy[m]{2(设     = = N i i i x t X D t 1 ( ) ( )  (   ( ))     ( )  (   ( ))    ( ) 1 1 1 m X D t c X D t k X D t m I x t g N i i i N i i i N i i i    +   +  = − = = =                (   ( ))      ( ) ( ( )) ( ( )) 1 1 1 X k X D t X m I x t X m X D t X c X D t g T j N i i i T j N i i i T j N i i i T j    + = − + +    = = =                     ( ) ( ) ( ) ( ) X m I x t X m X D t X c X D t X k X D t g T j j j T j j j T j j j T j    = − + + = 代入运动方程，得 方程两端左乘   T X j mx cx kx mIx (t) g  +  + = − 