Controller Design Using Root Locus: Example 10.12 Consider again the closed-loop position-control system presented below. Use the root locus to design a controller Gc(s) that provides a fast, well-damped closed- loop transient response to a reference step position command xref(t) = 0.1 m. The actuator gain is KA = 2 N/V. We worked on this system back in Example 1o.6, where the closed-loop responses were obtained with P-and PD-controllers. This example will illustrate how the root-locus plot allows the control engineer to visualize the effect of changing the controller dynamics without deriving the closed-loop characteristic equation
Reference position, Xref(t)
Position error, x(t)
Actuator voltage, ein(t) KA
Force, f(t)
Position, x(t)
Gc(s)
1
s2 + 0.3s
Controller
Actuator gain (N/V)
Mechanical
system dynamics