{a,b,c}={({{0.81,-0.23,-0.045},{0.09,0.98,-0.0023},{0.005,0.1,1}}),({{0.09},{0.0047},{0.00016}}),({{1,3.5,3}})};ss=StateSpaceModel[{a,b,c},SamplingPeriod->0.1];
l=EstimatorGains[ss,{0.5,0.6,0.75}];
ssobsv=StateSpaceModel[{a-l.c,l,IdentityMatrix[3]},SamplingPeriod->0.1];
stateResp=StateResponse[{ss,{1,-0.75,0.5}},{0},{t,6}];
y=OutputResponse[{ss,{1,-0.75,0.5}},{0},{t,6}];
obsvResp=OutputResponse[ssobsv,y];
tspan=Range[0,6,0.1];ListPlot[Replace[Join[stateResp,obsvResp],pts:{__}:>Thread[{tspan,pts}],{1}],PlotRange->All,PlotMarkers->{"*","o","@","+","#","x"},Epilog->Inset[Framed[Style[Column[{"*----\!\(\*SubscriptBox[\(x\), \(1\)]\)","+---\!\(\*SubscriptBox[\(x\), \(1  obs\)]\)","o----\!\(\*SubscriptBox[\(x\), \(2\)]\)","#----\!\(\*SubscriptBox[\(x\), \(2  obs\)]\)","@----\!\(\*SubscriptBox[\(x\), \(3\)]\)","x---\!\(\*SubscriptBox[\(x\), \(3  obs\)]\)"}],10]],{5,0.6}],AxesLabel->{"t"},ImageSize->350,Joined->True]