In the present paper an approach is presented to the speed control of
permanent magnet synchronous motors without mechanical transducers. Th
e rotor position, which is an essential component of any vector contro
l scheme, is calculated through the instantaneous stator flux position
and an estimated value of the load angle. A closed-loop state observe
r is implemented to compute the speed feedback signal. Experimental re
sults on a laboratory tested motor drive are presented to validate the
proposed procedure.