Nyquist stability theorem

Nyquist stability theorem

[′nī‚kwist stə′bil·əd·ē ‚thir·əm]
(control systems)
The theorem that the net number of counterclockwise rotations about the origin of the complex plane carried out by the value of an analytic function of a complex variable, as its argument is varied around the Nyquist contour, is equal to the number of poles of the variable in the right half-plane minus the number of zeros in the right half-plane. Also known as Nyquist stability criterion.