Traveling wave ultrasonic motor

A traveling wave ultrasonic motor comprising at least one ring-shaped stator (2), two groups of electromechanical transducers (3 to 6) each comprising at least one pair of diametrically opposed longitudinal transducers, polarized in opposite directions, disposed perpendicularly to the stator (2), that is to say parallel to the axis of the motor, distributed around the stator (2), in permanent contact with the stator (2) and excited by an alternating current with a π/2 phase shift between the groups so as to produce a traveling wave-like deformation on the surface of the stator (2), and at least one rotor (1) held elastically in contact with the stator (2) for the rotational driving thereof by the traveling wave produced on the stator, wherein the stator is in contact with the rotor only via at least one pair of equal and diametrically opposed segments (9, 10) whose aggregate span is at most equal to a wavelength of the traveling wave produced in the stator.