Tieying Zhou

Study of a Mini-Ultrasonic Motor with Square Metal Bar and Piezoelectric Plate Hybrid

A new mini-ultrasonic motor with a metal bar and piezoelectric plate hybrid as a stator has been studied. Four piezoelectric plates are bonded to four sides of the metal bar. The metal bar is made of brass and the piezoelectric plates are made of Pb(Zr–Ti)O3. The polarization direction is vertical to the piezoelectric plate. Compared with the cylindrical type of motor, the motor with a square cross-section makes polarization more sufficient and the signal wire easier to be welded. In this study, the modal and harmonic analyses of the stator were performed by using the Finite Element Method. The resonance frequency of the motor is about 100 kHz, the no-load revolution is above 6000 rpm and the maximum torque is about 60 µN m. This new mini-ultrasonic motor has potential applications.

An electric contact method to measure contact state between stator and rotor in a traveling wave ultrasonic motor.

Performances of ultrasonic motor (USM) depend considerably on contact state between stator and rotor. To measure the contact state in a traveling wave ultrasonic motor (TWUSM), a special test method is necessary. This paper develops a new method named electric contact method to measure contact state of stator and rotor in traveling wave type USM. The effects of pre-load and exciting voltage (amplitude) of stator on contact state between stator and rotor are studied with this method. By a simulating tester of friction properties of TWUSM, the variations of stalling torque and no-load speed against the pre-load and the exciting voltage have been measured. The relative contact length that describes the contact characteristic of stator and rotor is proposed. The relation between the properties of TWUSM and the contact state of stator and rotor are presented. Additionally, according to a theoretical contact model of stator and rotor in TWUSM, the contact lengths at given conditions are calculated and compared with the experimental results.

A cylindrical rod ultrasonic motor with 1 mm diameter and its application in endoscopic OCT

A tiny ultrasonic motor was constructed by using a piezoelectric ceramic cylindrical rod as a vibration generator of the stator. The fabricated tiny motor has a diameter of 1 mm, a length of 5 mm and a weight of 36 mg. The resonant frequency is 32 kHz with one fixed boundary or 83 kHz with two free boundaries. Four silver electrodes were deposited on the cylindrical surface. The spacing between two adjacent electrodes was carefully designed. A method was developed for the polarization of the stator. By using the bending vibration mode of the stator, the motor shows a performance with a speed of 1800 rpm and a stalled torque of 4 μNm, and can bear a high driving voltage up to 350 Vpp. The motor was used to drive an optical prism for circular scanning in an endoscopic OCT system. The tomographic images of the inner cavities of a plastic tube and a scallion were obtained, and the resolution was of the order of micrometer-scale.

A study on the friction of a self-correction ultrasonic stepping motor.

An experiment has been carried out to investigate the self-correction function of a self-correction ultrasonic stepping motor. When a slider (rotor) is placed on a vibrating beam (stator), it will stay at a stable equilibrium position. If the slider is slightly moved off the equilibrium position, a restoring force will urge the slider back towards its equilibrium position. The experimental result shows that the position of the maximum restoring force on the slider differs from that predicted by using the linear theory. Study found that when a quadratic form is assumed for the dynamic friction coefficient, the theoretical and experimental results are in good agreement.

Piezoelectric Rod Micro Ultrasonic Motor with Shear-bending Modes

In this paper we propose a new mechanism for exciting shear-bending vibration in a piezoelectric ceramic rod. A mini-ultrasonic motor prototype with this concept was designed. Both finite element method (FEM) analysis and experimental results demonstrate the concept.

The measurement on vibration friction coefficient of ultrasonic motor

An ultrasonic motor (USM) of the friction type is driven by the friction force between the stator and the rotor. However the classical Coulomb friction law can not be used to explain the driven mechanism of an ultrasonic motor under the condition of high frequency vibration between the stator and the rotor. In our early study[1], a vibration friction model was offered to explain a phenomenon in an experiment of an ultrasonic motor, in which the friction coefficient was considered as a function of the vibration amplitude. In this paper, we show some experimental results to verify our vibration friction model. The vibration amplitude of the stator is measured by using a laser vibrometer, and the results show that it is proportional to the input voltage. The tangential friction force between the stator and the rotor is measured by changing the input voltages under various normal pre-load. The friction coefficient is calculated according to its definition, namely the tangential friction force divide by the normal force. With the increasing of the input voltage or says the amplitude, it is found that the vibration friction coefficient decreases. The experimental results are in a good agreement with the theoretical calculations. The vibration friction model would be used to explain the driven mechanism of an ultrasonic motor in a further work.

A Nut-Type Ultrasonic Motor Driven with Single Phase Signal

Most travelling wave ultrasonic motors use two phase signal with a 90° time phase difference to generate a traveling wave, this paper propose a novel nut-type travelling wave ultrasonic motor which uses only a single phase driving signal to excite two bending modes in r − θ plane of a nut-type stator simultaneously. Thus, both the motor structure and the driving circuit will be simplified. The working principle of the new single phase drive traveling wave nut-type ultrasonic motor was described. The working modes are observed with a finite element method software. A prototype nut-type ultrasonic motor was fabricated, and its electrical impedance was tested to observe the two working modes. The prototype motor worked at frequencies between two resonance frequencies under single phase drive as expected, and it also rotated bi-directional successfully.

An ultrasonic actuator working under cryogenic and vacuum circumstance

In this work, we present an ultrasonic actuator that can work under cryogenic vacuum environment. It can be used for adjusting distance between capacitor electrodes in high temperature superconductor filter (HTSF) to tune its pass-band. The actuator is an single crystal chips driven nut-type ultrasonic motor, which can work under cryogenic vacuum conditions. The stator of a nut-type ultrasonic motor is a nut-shaped octagon with internal thread, which matches with the rotor external thread and a bottom at one end as fixing base. Piezoelectric chips are glued to the sides of the octagon to generate a traveling wave along the circumference. Vibration of the stator drives the rotor to rotate via friction between thread interfaces and the thread drives the rotor to move along the axis direction. The actuator that we developed can easily acquire micrometer positioning accuracy, which enables it to tune the pass-band of a HTSF effectively. The motor was optimized with FEM harmonic response analysis. The mechanic...

A tiny ultrasonic motor used in an OCT endoscope

To minimize the micro-motor and simplify its fabrication for the demand in research and application, A cuboidal micro-ultrasonic motor with truncated edge was developed on the basis of a cylindrical micro-ultrasonic motor reported previously. Structure and working principle of the micro-motor and the method of polarization on the piezoelectric plate are introduced in this paper. The frequency of bending vibration mode were simulated by using a finite element analysis. Since the distribution of polarization electric field was not uniform, the influence of polarization voltage on piezoelectricity coefficient was taken into consideration, and the optimal length of truncated edge was calculated. The motor was fabricated and measured. The no-load rotation speed is 2460 rpm and stall torque is about 3.5 mum, when the driving voltage is 65 Vp-p. The cuboidal micro-ultrasonic motors have been utilized in a prototype of optical coherence tomography endoscope. The chicken esophagus and trachea in vitro were examined. The axial resolution is 25 mum and the lateral resolution is 30 mum. This motor has shown good performance, which has potential applied values.