what if I get multiple gain margin after lag-lead compensator, one is positive whereas the other is negative, however, the closed loop system is still stable, what does it means?
Aryan Jebelli If the gain is always less than one then you cannot determine a phase margin. Also, you cannot intersect the minus point with s=jw which tells you the poles cannot cross from RHP to LHP or vice-versa! Anthony
Cero Hierro This means you cannot solve GK=-1 with s=jw, so you cannot find a gain such that a closed-loop pole is on the imaginary axis. Usually this would also mean that the gain margin is infinite so the system is closed-loop stable for positive K.Anthony
Fantastic video, thanks John.
How do you switch from plot to plot at 14:00
Thanks very much! Just what I needed
what if I get multiple gain margin after lag-lead compensator, one is positive whereas the other is negative, however, the closed loop system is still stable, what does it means?
You will need to look at the Nyquist diagram to get further insight via the encirclements.
Anthony
what happens if the gain plot doesnt intercept 0 dB, im assuming phase will just be infite?
Aryan Jebelli If the gain is always less than one then you cannot determine a phase margin. Also, you cannot intersect the minus point with s=jw which tells you the poles cannot cross from RHP to LHP or vice-versa!
Anthony
what if the phase plot doesnt intercept -180º?
Cero Hierro This means you cannot solve GK=-1 with s=jw, so you cannot find a gain such that a closed-loop pole is on the imaginary axis. Usually this would also mean that the gain margin is infinite so the system is closed-loop stable for positive K.Anthony
gracias!
thank you :)