The IsSystem command checks the validity of the system object.

If sys is a valid system object, return true. If sys contains errors, return false.

To determine the problem with a system that fails, use DynamicSystems[Verify].

$\mathrm{with}\left(\mathrm{DynamicSystems}\right)\:$

$\mathrm{sys1}≔\mathrm{NewSystem}\left(\right)\:$

$\mathrm{PrintSystem}\left(\mathrm{sys1}\right)$

$\left[\begin{array}{l}\mathbf{Algebraic\; Equation}\\ \mathrm{continuous}\\ \mathrm{1\; output(s);\; 1\; input(s)}\\ \mathrm{inputvariable}\=\left[u\left(t\right)\right]\\ \mathrm{outputvariable}\=\left[y\left(t\right)\right]\\ \mathrm{ae}\=\left[y\left(t\right)=u\left(t\right)\right]\end{array}\right.$

$\mathrm{IsSystem}\left(\mathrm{sys1}\right)$

$\mathrm{true}$

$\mathrm{sys2}≔\mathrm{NewSystem}\left(\frac{s}{s^3+5s^2+7s+6}\right)\:$

$\mathrm{sys2}:-\mathrm{tf}≔⟨⟨\frac{\exp \left(s\right)}{s^3+5s^2+7s+6}⟩⟩\:$

$\mathrm{PrintSystem}\left(\mathrm{sys2}\right)$

$\left[\begin{array}{l}\mathbf{Transfer\; Function}\\ \mathrm{continuous}\\ \mathrm{1\; output(s);\; 1\; input(s)}\\ \mathrm{inputvariable}\=\left[\mathrm{u1}\left(s\right)\right]\\ \mathrm{outputvariable}\=\left[\mathrm{y1}\left(s\right)\right]\\ {\mathrm{tf}}_{1,1}\=\frac{{\ⅇ}^s}{s^3+5s^2+7s+6}\end{array}\right.$

$\mathrm{IsSystem}\left(\mathrm{sys2}\right)$

$\mathrm{true}$

$\mathrm{tf\_mimo\_z}≔\mathrm{Matrix}\left(\left[\left[\frac{1}{z^2}\,\frac{z^2}{z^3+5z^2+7z+6}\right]\,\left[\frac{1}{z}\,\frac{c}{z^2+az+b}\right]\right]\right)\:$

$\mathrm{sys3}≔\mathrm{NewSystem}\left(\mathrm{tf\_mimo\_z}\,\mathrm{discrete}\,\mathrm{sampletime}=0.001\,\mathrm{systemname}=''Sample\; discrete\; MIMO\; system''\right)\:$

$\mathrm{PrintSystem}\left(\mathrm{sys3}\right)$

$\left[\begin{array}{l}\mathbf{Transfer\; Function}\\ \mathrm{discrete;\; sampletime\; =\; .1e-2}\\ \mathrm{systemname}\=\mathrm{Sample\; discrete\; MIMO\; system}\\ \mathrm{2\; output(s);\; 2\; input(s)}\\ \mathrm{inputvariable}\=\left[\mathrm{u1}\left(z\right)\,\mathrm{u2}\left(z\right)\right]\\ \mathrm{outputvariable}\=\left[\mathrm{y1}\left(z\right)\,\mathrm{y2}\left(z\right)\right]\\ {\mathrm{tf}}_{1,1}\=\frac{1}{z^2}\\ {\mathrm{tf}}_{2,1}\=\frac{1}{z}\\ {\mathrm{tf}}_{1,2}\=\frac{z^2}{z^3+5z^2+7z+6}\\ {\mathrm{tf}}_{2,2}\=\frac{c}{z^2+az+b}\end{array}\right.$

$\mathrm{IsSystem}\left(\mathrm{sys3}\right)$

$\mathrm{true}$