如圖所示的單位反饋隨動(dòng)系統(tǒng),K=16s-1,T=0.25s,試求: (1)特征參數(shù)和ζωn; (2)計(jì)算σ%和ts; (3)若要求σ%=16%,當(dāng)T不變時(shí)K應(yīng)當(dāng)取何值?