Vector control has been widely used in control of permanent magnet synchronous motors (PMSM). This technique requires an accurate knowledge of the rotor position. In many applications, such as mini-UAV, it is not possible to install any mechanical sensor. Therefore, a sensorless technique using position observer has to be implemented in order to estimate the rotor position. In this paper, we propose a new observer for PMSM sensorless control: the position estimate is generated upon electromagnetic relations (dynamics of magnetic flux in the motor) in the two-phase stationary reference frame. The implementation of the proposed observer is not a real burden; its validity is experimentally tested and satisfactory results are obtained regarding real position (and speed set-point) tracking in different operating situations.