Abstract
This paper reviews sensorless algorithms for both induction motors and
permanent magnet motors using the active flux model, such that any
design applicable for non-salient pole ac motors can also be included in
the review framework. The proposed review framework classifies all
sensorless algorithms following a five-layer hierarchy abbreviated as
O-I-M-A-I, resulting in four main categories as i) inherently sensorless
position estimation, ii) non-inherently sensorless position estimation,
iii) post-position-estimation speed estimation, and iv) speed estimation
for indirect field orientation. Various ac motor models are derived by
assuming a constant active flux amplitude, based on which seven generic
sensorless algorithms are summarized in a tutorial. Recommendations are
made for sensorless drive designers to begin with inherently sensorless
method such that the two-way coupling between position estimation and
speed estimation is avoided. Finally, classical induction motor model
results from time-varying active flux amplitude and slip relation, for
which a state transformation is recommended for achieving global
stability.