In this chapter, techniques are described for assessing the relative stability of a multivariable control system design. An interesting and important feature in multivariable feedback systems is that they have different stability margins at different points in their configuration. According to the generalized Nyquist stability criterion the feedback system is stable if, and only if, the number of anticlockwise encirclements of the critical point -1 by the characteristic gain loci, is equal to the number of open-loop unstable poles.

Inspec keywords: Nyquist stability; control system synthesis; Nyquist criterion; multivariable control systems

Other keywords: multivariable control system design; multivariable feedback systems; relative stability; Nyquist stability criterion; time-invariant system; open-loop unstable poles; multivariable control system relative stability

Subjects: Multivariable control systems