R(S) On C(s) S(S+2EOn) 上讲回顾 欠阻尼0<5< 图3-8标准形式的二阶系统方块图 h(t)=1 sn(oat+B),t≥0 2 B=arct arccos B 过阻尼 h(tn)-h(∞) h(∞)×100%=e ×100% 2>1当T≥472ts=371 丌-B 4.751 3.5 4.5 △=0.05 △=0.02上讲回顾 arccos 1 2 = − = arctg 1 2 1− sin( ) , 0 1 1 ( ) 1 2 + − = − − h t e t t d t n d r t − = 100% 100% ( ) ( ) ( ) % 2 1 = − = − − e h h t p h S(S+2ξωn) ωn R 2 (s) C(s) 图3-8 标准形式的二阶系统方块图 _ 过阻尼 1 1 1 2 1 1 4.75 1 4 3 t T T T t T S S = = = 当 欠阻尼 0 1 d p t = 0.05 3.5 = = n s t 0.02 4.5 = = n s t 2 d =n 1−