  In this work, we present a mixed sensorless strategy for Permanent Magnets
Synchronous Machines, combining a torque/current controller and an observer for
position, speed, flux and stator resistance. The proposed co-design is
motivated by the need of an appropriate signal injection technique, in order to
guarantee full state observability. Neither the typical constant or
slowly-varying speed assumptions, nor a priori mechanical model information are
used in the observer design. Instead, the rotor speed is modeled as an unknown
input disturbance with constant (unknown) sign and uniformly non-zero
magnitude. With the proposed architecture, it is shown that the torque tracking
and signal injection tasks can be achieved and asymptotically decoupled.
Because of these features, we refer to this strategy as a sensorless
controller-observer with no mechanical model. Employing a gradient descent
resistance/back-EMF estimation, combined with the unit circle formalism to
describe the rotor position, we rigorously prove regional practical asymptotic
stability of the overall structure, with a domain of attraction that can be
made arbitrarily large, not including a lower dimensional manifold. The
effectiveness of this design is further validated with numerical simulations,
related to a challenging application of UAV propellers control.
