About robustness of the reduced order Luenberger observer

Using a special determination of the state variables it is noted, that with the faster modes of the conventional reduced order Luenberger observer, a smaller sensitivity to the change of the plant parameters is related. Especially, for the plants with single input and single output (SISO) and no zeros, it is shown that the sufficiently fast observer has a negligible sensitivity to all of the plant parameters. For the SISO plants with some zeros, the number of the plant parameters with respect to which the observer is almost insensitive decreases, if the number of zeros increases. The considerations are extended to the plants with multiple inputs and single output (MISO) and to the MIMO plants. These observations are confirmed by the enclosed results of simulations.