MATLAB: Are there extra zeros in the num and den fields of the transfer function in Control System Toolbox 8.1 (R2008a)

Control System Toolboxextrafunctiontftransferz^-1zeros

I created a transfer function using variable "z^-1" and multiplied it by a transfer function in "z". The resulting transfer function have extras zeros in the 'den' and 'num' vectors:
h = tf([0 1 2 3],[1 0 0 0],0.1,'variable','z^-1');
Z = tf( [ 1 0 ], [1], 0.1, 'variable', 'z' );
g=h*Z;
get(g)
             num: {[1 2 3 0]} 
             den: {[1 0 0 0]}

Best Answer

The ability to automatically simplify rational expressions on LTI objects is not available in the Control System Toolbox 8.1 (R2008a).
To work around this issue it is possible to perform pole/zero cancellation for the system using the command MINREAL
minreal(g)
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