Quiz
8: Frequency - 2
Name:_____________________________
Shown below is the Nyquist plot for a system with an open loop transfer
function, KG(s). The proportional controller, K, and G(s) are embedded
in a closed loop system as shown below. G(s) is a stable transfer
function.

Answer the following
questions
-
As shown, the KG(s) plot
below is drawn for K = 1. Is the system stable (i.e. are all of the
closed loop poles in the LHP?) for a gain of K = 1?
-
If the gain, K, is changed
to a value K = 0.3, then:
-
Sketch the KG(jw)
plot for K = .3. Your sketch should be drawn on the plot below.
-
Label any important points
(DC point, etc.) giving values as best possible (not 5 place accuracy!).
-
Determine - using your
sketch - if the system is stable for K = 0.3.
-
Determine - using the
ideas in doing your sketch - the range of gains for which the system is
stable.
-
Determine how many closed
loop poles are in the RHP.
-
From the sketch, determine
as many aspects of G(s) as you can. (Things like DC gain, # poles,
etc.)