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Remotely Control a Cooling Fan

The model for controlling a ventilation fan can include several delays:
Wolfram Language code: {fan, sensing, actuator, com, controller} = {StateSpaceModel[{{{-(1/10)}}, {{1}}, {{(1/10)}}, {{0}}}, SamplingPeriod -> None, SystemsModelLabels -> None], TransferFunctionModel[Unevaluated[{{E^-s δ}}], s, SamplingPeriod -> None, SystemsModelLabels -> None], TransferFunctionModel[{{{E^(-1/10*s)}}, 1}, s, SamplingPeriod -> None, SystemsModelLabels -> None], TransferFunctionModel[{{{E^(-1/2*s)}}, 1}, s, SamplingPeriod -> None, SystemsModelLabels -> None], TransferFunctionModel[Unevaluated[{{(25 + 22s/s)}}], s, SamplingPeriod -> None, SystemsModelLabels -> None]};
A controller that works on the fan directly may fail when delays are present:
Wolfram Language code: y0 = OutputResponse[SystemsModelFeedbackConnect[SystemsModelSeriesConnect[controller, fan]], UnitStep[t - 2], {t, 0, 20}]; Plot[y0, {t, 0, 20}, PlotRange -> All]
Wolfram Language code: remotesys = SystemsModelSeriesConnect[actuator, SystemsModelSeriesConnect[fan, sensing]]; comsys = SystemsModelSeriesConnect[SystemsModelSeriesConnect[com, remotesys], com]
Wolfram Language code: y1 = OutputResponse[SystemsModelFeedbackConnect[SystemsModelSeriesConnect[controller, comsys /. δ -> 1 / 5]], UnitStep[t - 2], {t, 0, 10}]; Plot[%, {t, 0, 10}, PlotRange -> All]
The closed-loop fan with a Smith predictor has the same characteristics as the delay-free fan:
Wolfram Language code: smith = SmithDelayCompensator[comsys, controller]; cl2 = SystemsModelFeedbackConnect[SystemsModelSeriesConnect[smith, comsys]];
Wolfram Language code: responses = Prepend[Table[OutputResponse[cl2 /. {δ -> del}, UnitStep[t - 2], {t, 0, 20}], {del, {1 / 5, 5, 10, 15}}], y0];
Wolfram Language code: Plot[responses, {t, 0, 20}, PlotRange -> All, PlotStyle -> Prepend[Table[Dashed, {4}], Thick], ImageSize -> Medium]