Talk:Control Systems/Controllability and Observability

It seems the definition of control-ability an reachability are misplaced by each other.

Possible error in section 'Duality principle'
The affirmation 'We can say that a system (A, B, C, D) is controllable if and only if the system (A', C', B', D) is observable.' is only true if the system is LTI. For the more general linear time-varying case, (A, B, C, D) is controllable if and only if the system (-A',C',B',D) is observable.

Saung Tadashi (discuss • contribs) 03:07, 4 March 2013 (UTC)