Week 10
Nyquist and Stability Margins
I follow the saved course materials and calculations from modeling through stability, root locus, and frequency response.
What I connect in this unit
The Nyquist criterion combines encirclements of -1 by the open-loop response with the number of open-loop right-half-plane poles to determine closed-loop stability. The same curve relates distance and angle to gain and phase margins.
Concept map
- Nyquist contours
- Encirclement
- Gain margin
- Phase margin
Technical anchor
Fix the contour direction and encirclement sign convention before applying the N, P, Z relation. Use the unit-magnitude crossing for phase margin and the negative-real-axis crossing for gain margin.
How I review it
Plot the positive-frequency path, complete the negative-frequency half by conjugate symmetry for a real system, and inspect the neighborhood of -1 for crossings and encirclement direction.
Connection to the full course
Unit 10 of 12. Unit numbers organize the concepts found in the materials and do not reproduce an attendance schedule.