Graphical stability criteria for nonlinear multiloop systems

In this paper a description of a certain class of multiloop systems, called the Standard Multiloop Form, is introduced. This description is expressed explicitly in terms of certain scalar subsystems and can be shown to include many of the common descriptions of multiloop systems. The stability criteria presented in this paper involve the individual Nyquist plots of the linear scalar subsystems and a certain positivity condition on the nonlinear subsystems. The method allows for relatively convenient computations. The derivation depends on the hyperstability concept introduced by V. M. Popov.