  Robustness of linear systems with constant coefficients is considered. There
exist methods and tools for analyzing the stability of systems with random or
deterministic uncertainties. At the same time, there are no approaches for the
analysis of systems containing both types of parametric uncertainty. The types
of robustness are reviewed and new type of "mixed parametric robustness" is
introduced. It includes several variations. The proposed formulations of mixed
robustness problems can be considered as intermediate type between the
classical deterministic and probabilistic approaches to robustness. Several
cases are listed in which the tasks are easily solved. In general, tests of the
stability of robust systems using the scenario approach are applicable, but
these tests can be computationally complex. To calculate the desired stability
probability, a simple graphical approach based on a robust D-partition is
proposed. This method is suitable for the case of a small number of random
parameters. The final estimate of the probability of stability is calculated in
a deterministic way and can be found with arbitrary precision. Approximate ways
of solving the assigned tasks are described. Examples and generalization of
mixed robustness to other types of systems are given.
