0 t≤1 d ic(t=c- 41<t≤2 dt 42<t≤4 0 t>4 t<1 4(t-1)1<t≤2 Pc(t)=uc(tic(t) (W) 4(t-3)2<t≤4 t>4t u i t C d d ( ) C C = ( ) 0 4 4 2 4 4 1 2 0 1 A t t t t           −    = ( ) 0 4 4( 3) 2 4 4( 1) 1 2 0 1 ( ) ( ) ( ) C W t t t t t t p t u t i t C C         −   −    = =