Stability radius
In mathematics, the stability radius of an object (system, function, matrix, parameter) at a given nominal point is the radius of the largest ball, centered at the nominal point, all of whose elements satisfy pre-determined stability conditions. The picture of this intuitive notion is this: where p ^ {\displaystyle {\hat {p}}} denotes the nominal point, P {\displaystyle P} denotes the space of all possible values of the object p {\displaystyle p} , and the shaded area, P ( s ) {\displaystyle P(s)} , represents the set of points that satisfy the stability conditions.