Abstract: Disclosed is a motor drive device with tacho-generator that can be configured as a back-up motor. This device is designed for the driving of a movable element. It comprises an electrical rotor motor with supply coil, associated with a tachometrical sensor inducing an electrical current in at least one electrical coil, a regulator circuit controlling the speed and the position of the electrical motor as a function of the servo signal delivered by said electrical coil and applied to the supply coil. This device further comprises means to continue the driving of the movable element in the event of the malfunctioning of the electrical motor or of its electrical supply. These means to continue the driving of the movable element are constituted by a failure detection circuit which, in the event of failure, activates switching means to connect the electrical coil of the tachometrical sensor to an electrical supply source. Application: improvement of the safety of a motor drive mechanism.