Position detector of the rotor of a piezo-electric motor

Piezo-electric motor of the stationary wave type comprising:

• a stator including piezo-electric excitation means capable of inducing a vibratory motion in the stator,
• a rotor mounted for rotation relative to the stator, said rotor including a body on which are assembled, in a regular pattern, a plurality of flexion tabs forming transmission means arranged to transmit the vibratory motion of the stator to said rotor and to rotationally drive such rotor, said flexion tabs following a displacement path relative to the stator, and further comprising:
• an angular position detector for detecting the angular position of the rotor, said detector being arranged near and in line with said displacement path, said detector comprising at least one piezo-electric sensor for tracking the passage of said tabs by measuring deformations of the stator induced by a force exerted individually by each tab of the rotor during its passage on or near the detector so as to produce an electric signal having a periodicity depending on the rotational speed of the rotor and on the number of tabs as well as the distance between the tabs, said electric signal being representative of the position of the tabs and thus of the angular position of the rotor.