In recent years, many automatic control systems for guided vehicles in factories have been installed. One system uses a guidance cable embedded in the floor to guide the vehicle along the desired lane $[10$, $15]$. An error detector, composed of two coils mounted on the front of the cart, senses a magnetic field produced by the current in the guidance cable. An example of a guided vehicle in a factory is shown in Figure P7.19(a). We have
$$
G(s)=\frac{s^2+3.6 s+81}{s(s+1)(s+5)}
$$
and $K_a$ is the amplifier gain. (a) Sketch a root locus and determine a suitable gain $K_a$ so that the damping ratio of the complex roots is 0.707 . (b) Determine the root sensitivity of the system for the complex root $r_1$ as a function of (1) $K_a$ and (2) the pole of $G(s)$ at $s=-1$.