The problem under interest is the linearization of nonlinear MIMO syst
ems by generalized input-output injection in order to design observers
with linear error dynamics. The method is based on the study of the s
tructure of the input-output differential equations; thus, the problem
is solved as a realization problem. In this note, one considers the l
inearization under two kinds of input-output injection. In the first c
ase, the transformation depends on the output and time derivatives of
the input, whereas in the second case, derivatives of both the input a
nd the output are considered. Necessary and sufficient conditions are
obtained which generalize the ones on standard input-output injection
linearization. (C) 1997 Elsevier Science B.V.