Research On Mathematical Driving Model Of Ultrasonic Motor And Its Frictional Materials

Piezoelectic ultrasonic motors(USM) exhibit advantages over conventional electromagnetic motors, such as high retention torque, high torque at low speed, high compactness in size and none of electromagnetic interferences. Since last decade, applications of USM have attracted considerable attention in focusing mechanisms, precise positioning tables, and robot actuators, etc.USM is involved with many fields and regarded as a typical high-tech mechtronics product in spite of its short history. In this paper, firstly the history and actuality of USM are illuminated .And the difficulties and the key points of the technique on USM are presented. Then how USM works and how the ellipse trace of particle on the surface of stator forms are analyzed. The mathematical model of USM can be divided into two parts. One is one-dimensional model for stator vibrations, and another is frictional driving model between stator and rotor. On the basis of literature, the model for stator vibration is testified and the thought applied to the attestation is given. The micro driving mechanism between stator and rotor is analyzed and the frictional driving model is founded .The precondition and components of the model are made clearly. The relation between two kinds of model is also explained. The whole system of the mathematical model of USM is formed.At the same time, research on USM frictional material is carrying out for a TWUSM.Firstly ,a series of wearproof thin films are fabricated by Magnetic Filter anode vacuum arc source.The characteristics of binding force, micro-scale rigidity associated with surfaces are measured under laboratory conditions.The friction and wear behavior of the surface of these films in dry sliding against steel is examined on a pin-on-disk test rig. Secondly, the performance of friction couples are tested under the condition of USM running. The morphologies of the worn surface and the wear mechanism of the surface are observed and analyzed by means of SEM and EDX .The results show that the frictional material has lots of properties,suchas no adhesion and debris discharging easily, low temperature ascending and high output torque without fluctuating.