Linear ultrasonic motor and constant pre-pressure applying method thereof

The invention discloses a linear ultrasonic motor and a constant pre-pressure applying method thereof. The motor comprises a base, a stator, a sliding block, a first positioning column, a second positioning column, a first rotating shaft, a second rotating shaft, a third rotating shaft, a guide cylinder, a threaded push rod, a spring and a rotating head. The threaded push rod comprises a screw rodand a polished rod which are coaxially and fixedly connected in sequence; the screw rod is in threaded connection with the rotating head; the polished rod is in clearance fit with the inner wall of the guide cylinder; and the spring is arranged in the guide cylinder and abuts against the closed end of the guide cylinder and the polished rod . The first positioning column is rotationally connectedwith the rotating head; the closed end of the guide cylinder is rotationally connected with one clamping end of the stator; the second positioning column is rotationally connected with the other clamping end of the stator; a driving foot of the stator abuts against the sliding block. The quasi-zero static stiffness characteristic can be achieved, and the pre-pressure of the linear ultrasonic motor is kept constant, so that the stability of the motor in the operation process is guaranteed, and the influence of machining errors of the motor, abrasion caused by operation of the motor and the like on the pre-pressure can be eliminated.