Pl. Jansen et Rd. Lorenz, A PHYSICALLY INSIGHTFUL APPROACH TO THE DESIGN AND ACCURACY ASSESSMENT OF FLUX OBSERVERS FOR FIELD-ORIENTED INDUCTION MACHINE DRIVES, IEEE transactions on industry applications, 30(1), 1994, pp. 101-110
Rotor flux observers can provide an attractive means for achieving dir
ect field oriented control of induction machines. This paper presents
a physics-based design methodology and uses it to evaluate open-loop o
bservers and to develop a new closed-loop flux observer. It is shown t
hat the new flux observer is a straightforward structure with properti
es that combine the best features of known methods. A distinction is m
ade between observers, which use only integration and feedback summati
on operations, and those estimation methods requiring approximate diff
erentiation which are, in essence, ''cancellation'' methods. Furthermo
re, a clear distinction is made between accuracy and dynamic robustnes
s of the observer. This distinction is important because the accuracy
of flux observers for induction machines is inherently parameter sensi
tive. Whereas robustness of observers, in a controls sense, is not par
ameter sensitive. Moreover, it is shown how flux observers can provide
robust field oriented control because the flux angle is substantially
more correct than the flux magnitude. A distinctive form of frequency
response function (FRF) analysis similar to that used in classical co
ntrol engineering is demonstrated to be a useful and insightful tool e
ven though flux observers are multiple-input, multiple-output systems.
Finally, the limits of such flux observers are experimentally evaluat
ed.