A direction method for stability robustness analysis with respect to real uncertain parameters

A direction method is developed in this study to characterize stability rob ustness of a nominal stable control system subject to perturbations of real uncertain parameters. In this direction method, characteristic loci of dir ectional stability robustness matrices are used to infer directional stabil ity margins. When only the number of the real uncertain parameters is given , these directional stability margins can be connected to form a stability region to characterize the stability robustness. When a parameter uncertain ty template is given, these directional stability margins can also be used to obtain a stability margin with no conservation. The advantage of this me thod is that it can be utilized to obtain a stability margin for varieties of real parameter uncertainty templates which is generally not possible in other approaches.