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U. Rieder, M. Schrödl, A. Ebner:
"Sensorless Control of an External Rotor PMSM in the Whole Speed Range including Standstill";
Poster: IEEE Annual Power Electronics Specialists Conference (PESC), Aachen, Germany; 2004-06-20 - 2004-06-25; in: "2004 IEEE 35th Annual Power Electronics Specialists Conference", (2004), ISBN: 07803-8400-8; 1280 - 1285.

In this paper a concept will be presented that
allows the control of an external rotor permanent magnet
synchronous machine by using DC-link current measurements
only. For position detection, sensorless methods using just DClink
measurements are implemented - the INFORM-method in
the low speed range including standstill and a back-emf based
model for high speed. DC-voltage measurements are useful in
case of varying DC-link voltage e.g. in generatoric mode. The
presented algorithms result in a sensorless high torque - lowcost
system that is vector controlled in the whole speed range
and hence has higher performance compared to sensorless
state of the art systems.
The algorithms are implemented on a 16bit DSP with PWM
and Capture/Compare-Units. The DC-link current
measurement is interrupt-based and thus a time critical event
that is triggered by the Capture/Compare-Units of the space
vector PWM. Its functionality, restrictions and limits are
explained and discussed in detail. In the low speed range the
PWM duty cycles are too short for interrupt-triggered DC-link
current measurements. In this operation area, the sequence of
the INFORM-method can directly be used to get current
information.
Furthermore the sensorless methods and their modifications
for using DC-link measurements only will be extensively
explained. Finally measurement results will be presented,
discussed and compared to a classical encoder-based vector
oriented machine with respect to accuracy and noise.

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