r(t)=-(1-cosm)n()*>[6(t-3m)-(t-3n-2 n=0 =(1-cosm)()-(-2)*∑8(=3m) 2一 01234567t                   0 0 (1 cos )[ ( ) ( 2)] ( 3 ) 1 (1 cos ) ( ) [ ( 3 ) ( 3 2)] 1 ( ) n n t u t u t t n r t t u t t n t n       