LowerBound of stabmarg = 1.0 what does this mean?

Hey there, I use Matlab 2014a. And want to find out if my system is robust stable. I did this by the command robuststab.

I got:

stabmarg =

LowerBound: 1.0000

UpperBound: 1.0000

DestabilizingFrequency: 4.5514

destabunc =

mu: 1.7245

r: 0.0419

My uncertainties:

r_u = ureal('r', 0.0298, 'Range', [20*e-3, 80*e-3]);

mu_u = ureal('mu', 0.0+1e-8, 'Range', [0.0, 0.1]);

The documentation says:

LowerBound

Lower bound on stability margin, positive scalar. If greater than 1, then the uncertain system is guaranteed stable for all values of the modeled uncertainty. If the nominal value of the uncertain system is unstable, then stabmarg.UpperBound and stabmarg.LowerBound both equal 0.

UpperBound

Upper bound on stability margin, positive scalar. If less than 1, the uncertain system is not stable for all values of the modeled uncertainty.

--> My LowerBound of 1 is not greater than 1 but equal to one. Does this mean that RS could not be proved?

--> Destabunc says that only for mu = 1.72 I have instability. But my mu is not even in this range? Does this mean my

sys is stable if mu and r are in the defined uncertainty ranges?

Thanks :)