marginal stability

The loop transfer function of a negative feedback system is $$ G(s) H(s)=\frac{K(s+11)}{s(s+2)(s+8)} $$ The value of $K$, for which system is marginally stable, is $\_\_\_\_$ .

A unity feedback control system is characterized by the open-loop transfer function $$$G\left(s\right)\;=\;\frac{2\left(s+1\right)}{s^3+ks^2+2s+1}$$$ The value of k for which the s...

A unity negative feedback system has the open-loop transfer function $$$G\left(s\right)\;=\;\frac K{s\left(s\;+\;1\right)\left(s\;+\;3\right)}$$$ The value of the gain K (>0) at wh...

The characteristic equation of a feedback control system is $$$s^4+20s^3+15s^2+2s+K\;=\;0$$$ (i) Determine the range of K for the system to be stable. (ii) Can the system be margin...