The system with the open loop transfer function G(s)H(s)=$${1 \over {s\left( {{s^2} + s + 1} \right)}},$$ has a gain margin of

The Nyquist plot of an all-pole second order open-loop system is shown in Figure. Obtain the transfer function of the system.

A unity feedback system has the plant transfer function G_p(s)=$${1 \over {\left( {s + 1} \right)\left( {2s + 1} \right)}}$$
(a) Determine the frequency at which the plant has a phase lah of 90^o.
(b) An intergral controller with transfer function G_c(s)=$${k \over s}$$ , isplaced in the forwardpath the value of k such that the compensated system has an open loop gain margin of 2.5.
(c) Determine the steady state errors of the compensated system to unit-step and unit-ramp inputs.

The transfer function Y(s)/U(s) of a system described by the state equations
$$\mathop x\limits^ \bullet $$(t) = -2x(t)+2u(t)
y(t) = 0.5x(t) is