0 Step force with finite raising time P(t) Po k屋 m 0 Response to p(t) Rise phase 0:e）s ·Constant phase 间--ma-me-小 目 主求2相季院 Step force with finite raising time  Response to p(t) • Rise phase • Constant phase   0 sin n r r n r p t t u t t t k t t                0 1 1 sin sin n n r r n r p u t t t t t t k t                  