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A 240-μm diameter ultrasonic micromotor is presented as a potential solution for an especially difficult task in minimally invasive neurosurgery, navigating a guidewire to an injury in the neurovasculature as the first step of surgery. The peak no-load angular velocity and maximum torque were 600 rad/s and 1.6 nN-m, respectively, and we obtained rotation about all three axes. By using a burst drive scheme, open-loop position and speed control were achieved. The construction method and control scheme proposed in this study remove most of the current limitations in minimally invasive, catheter-based actuation, enabling minimally invasive vascular surgery concepts to be pursued for a broad variety of applications. © 2012 American Institute of Physics.

Linear piezoelectric ultrasonic motors based on multimodal coupling are widely used for generating precision actuations; however, multimodal decoupling often occurs when environment temperature changes, which may result in actuation failure. In this work, a miniature, ring-shaped, linear piezoelectric ultrasonic motor operating in a single, in-plane E01 mode (zero node line along the circumference and one node line along the diameter direction) is proposed. Experimental results show that it can produce a maximum driving force of 2.7 N, a no-load moving speed of 56 mm/s, and a high positioning resolution of 0.1 lm in open-loop control. Advantages of simple structure, controllable micrometer-scale displacement, and large bidirectional working stroke indicate that the proposed linear motor has great potential for industrial applications, especially for precise actuations. [ABSTRACT FROM AUTHOR]

Piezoelectric applications such as ultrasonic motors, transformers and therapeutic ultrasonics demand high power generation with low losses, which is facilitated by "hard" ferroelectrics. Hardening of piezoelectric properties, characterized by high mechanical quality factor (Qm), is usually achieved by doping with lower valence elements, thereby tailoring the domain wall dynamics. In the present study, we demonstrate a hardening mechanism by developing composites of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) with ZnO inclusions, as an alternative to chemical modifications. A decrease in the saturation polarization and total strain, higher internal bias fields, lower hysteretic losses and a two-fold increase in Qm are observed in comparison to NBT-6BT. The composite with 0.1 mole ratio of ZnO exhibits the highest Qm of 320 with d33=125 pC/N and Kp=0.29. A one-to-one correspondence between the increase in Qm and the decrease in the domain wall mobility is established from the ac field dependence of permittivity, in the framework of the Rayleigh law. A further increase in ZnO content beyond a mole ratio of 0.1 reduces Qm, but retains it at a higher level, as compared to NBT-6BT. The results are explained based on the poling-induced strain incompatibility between the matrix and the hard ZnO phase. This composite approach is therefore considered a generic hardening concept and can be extended to other ferroelectric systems. [ABSTRACT FROM AUTHOR]

Lubrication has been proven to be an effective approach to drastically improve the efficiency of ultrasonic motors without losing the output torque. This phenomenon is attributed to the effective modulation of the friction force by lubricant, according to the theory described in the Stribeck curve. Previous findings even show a potential to increase the motor output torque with lubrication. Here, the torque enhancement of ultrasonic motors using lubricant is extensively studied in hybrid transducer-type ultrasonic motors (HTUSMs) with a size of 25mm in diameter. The lubricated HTUSMs could withstand static preload as high as 267N and maximum torque as large as 1.01N m was obtained with lubrication, which were 3.5 times and 2.6 times higher than those in dry condition, respectively. This result clearly reveals that lubrication can enable ultrasonic motors to be operated under much higher static preload and hence significantly improve the motor output torque, instead of only reducing the friction force. [ABSTRACT FROM AUTHOR]

We report a face-shear mode ultrasonic motor (USM) made of [011]c poled Zt ± 45° cut 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 single crystal, which takes advantage of the extremely large d36 = 2368 pC/N. This motor has a maximum no-load linear velocity of 182.5 mm/s and a maximum output force of 1.03 N under the drive of Vp = 50 V, f = 72 kHz. Compared with the k31 mode USM made of Pb(Zr,Ti)O3 (PZT), our USM has simpler structure, lower driving frequency, much higher electromechanical coupling factor, and twice power density. This USM can be used for low frequency operation as well as cryogenic actuation with a large torque. [ABSTRACT FROM AUTHOR]

In order to overcome many shortcomings of the traditional contact-type rotors, noncontact ultrasonic motors, which are driven by acoustic streaming, have been proposed. Recently, an analytical solution based on the second order approximation has been presented, but it gives a revolution speed five times smaller than the experimental value. In order to reconcile the discrepancy, the authors perform numerical simulations of the gas motion between the stator and the rotor driven by the acoustic streaming. With the same parameters used in the experiment, it is found that the acoustic streaming can account for the observed fast rotation. [ABSTRACT FROM AUTHOR]

Two cylinder-shaped ultrasonic motors 4.8 mm in diameter were developed. This kind of motor was driven by four pieces of piezoelectric materials, which were used to excite the two first-bending vibrations. Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystal and Pb(Zr,Ti)O3 (PZT) ceramic piezoelectric materials were used as drive elements. The motor based on PMNT crystals could operate at a voltage of 25 Vp-p (peak to peak). When driven by a 100 Vp-p voltage, the motor could run at frequency ranging from 26 to 68 kHz and the revolution speed reached 450 rpm. Its maximum output torque was 0.6 mN m. The motor based on the PZT ceramic did not exhibit high performance as the PMNT crystal motor. The piezoelectric materials affect the performance of the motors greatly. [ABSTRACT FROM AUTHOR]

Describes a piezoelectric motor combining the merits of piezoelectric materials. Use of a direct coupling mechanism between that stator and rotor; Transmission of the whole power generated in the piezoelectric element to the rotor.

We report a piezoelectric standing wave linear ultrasonic motor with double driving tips for generating precision motion. The motor's piezoelectric actuator was made of a simple Pb(Zr,Ti)O3 square-plate (15 × 15 × 2 mm3) operating in a single face-diagonal-bending standing wave mode to produce symmetric, bi-directional linear motion. The motor generated a driving force of 3.0 N and a moving speed of up to 165 mm/s under a relatively low applied electric field of 75 Vpp/mm at a resonance frequency of 141.5 kHz. This motor is superior to those previously reported because of the double friction-tip standing wave driving mechanism and the operating mode. [ABSTRACT FROM AUTHOR]