User`s guide

8 The Root Locus Design GUI
8-14
unstable if the gain set point is increased so as to place any of the closed-loop
poles in the right-half of the complex plane.
You can test the limits of stability by either:
• Dragging the closed-loop poles around the locus to change the gain set point
• Changing the gain set point manually
In this example we do the former.
Dragging Closed-loop Poles to Change the Gain Set Point
To see by how much the gain can be increased while maintaining the
closed-loop poles in the left-half of the complex plane:
1 Move the mouse pointer over a red square marking one of the complex poles
nearest the imaginary axis. N otice how the pointer becomes a hand.
2 Grab the closed-loop pole by holding down the left mouse button when the
hand appears.
3 Drag the pole close to the imaginary axis.
4 Release the mouse button. The gain changes as the closed-loop set point is
recomputed.