For a LTVC system with transition matrixΦAā we define the controllability GramianW(t0ā,t1ā) as W(t0ā,t1ā)=t0āā«t1āāΦAā(t0ā,Ļ)B(Ļ)Bā¤(Ļ)ΦAā¤ā(t0ā,Ļ)dĻ
Consider an LTIC system with Controllability GramianW(t0ā,t1ā). Then. we have that Ker(W(t0ā,t1ā))=Ker(WTā)andImage(W(t0ā,t1ā))=Image(WTā)where WTā=[B,AB,A2B,ā¦,Anā1B][B,AB,A2B,ā¦,Anā1B]TIn particular, Image(W(t0ā,t1ā)) and Ker(W(t0ā,t1ā)) are independent of t0ā and t1ā.