Howtosignalprocessing
- What is the gain at the origin of the Nyquist plot?
- How do you interpret a Nyquist plot?
- What is Nyquist contour and the effect of poles at the origin?
- How do you know if a system is stable from a Nyquist plot?
What is the gain at the origin of the Nyquist plot?
The frequency at which the Nyquist plot is having the magnitude of one is known as the gain cross over frequency. It is denoted by ωgc. The stability of the control system based on the relation between phase cross over frequency and gain cross over frequency is listed below.
How do you interpret a Nyquist plot?
With a Nyquist plot, you can simply observe the distance between (–1, 0) and the point at which the curve crosses the negative real axis. More distance between these two points corresponds to a larger gain margin and, consequently, to a circuit that is more reliably stable.
What is Nyquist contour and the effect of poles at the origin?
For a single pole at the origin, the Nyquist curve will approach infinity as approaches zero from both the positive and negative direction. The Nyquist curve can then be "closed" by tracing around a small semicircle to the left of the pole (as shown in Figure 9.3a).
How do you know if a system is stable from a Nyquist plot?
The greater the gain margin, the more stable the system. If the gain margin is zero, the system is marginally stable. (Note: the text also shows that the Nyquist plot crosses the real axis when the Nyquist path is going through the point s=j3.
