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A new T-shape piezoelectric motor using the hybrid of two orthogonal longitudinal vibrations is proposed in this work. Six pieces of PZT ceramic plates are bonded on the upside and downside surfaces of a T-shape duralumin alloy base respectively to form the proposed motor. Elliptical movement can be generated on the driving tip by applying sine and cosine voltages to the PZT elements. The horizontal displacement of the driving tip will push the runner while the vertical displacement can overcome the preload. Finite element method is used to accomplish the design and analysis process. The resonance frequencies of the two vibration modes are tuned to be close by modal analysis, while the motion trajectory of the driving tip is observed by transient analysis. After the fabrication of a prototype, the vibration characteristics and mechanical output ability are measured. The no-load speed and the maximum output thrust force of the proposed motor are tested to be 718 mm/s and 3.5 N under an exciting frequency of 53.1 kHz. The proposed T-shape piezoelectric motor exhibits merits of simple structure, easy to realize miniaturization, easy to be fabricated, and high power-to-weight ratio.

A traveling wave ultrasonic motor utilizing a radial bending mode of a thick ring is proposed. Twenty PZT stacks and 20 block springs are nested alternately into 40 slots cut in the ring's outer surface to produce a traveling wave. The prototype achieves maximum speed and torque of 146 r/min and 1.0 N·m, respectively.

Pilot Channel without navigation message modulation is added in next generation GNSS for enhancing the acquisition performance in challenge environment. The pre-detection integration time of pilot channel is potential to exceed the bit width, so the receiver could obtain better acquisition sensibility. However, the benefit from pilot channel has not been thoroughly analyzed. The equivalent ideal detector factor is used to compare the performance of different power allocation options of data and pilot channel. The results show that when the data and pilot channel has the same power, the acquisition sensibility is not better than that of traditional signal in normal conditions. The conclusion has significance on the BDS modernized signal design.

To make full use of the vibrational energy of a longitudinal transducer, a rectangle-type linear ultrasonic motor with four driving feet is proposed in this paper. This new motor consists of four longitudinal vibration transducers which are arranged in a rectangle and form an enclosed construction. Lead zirconate titanate ceramics are embedded into the middle of the transducer and fastened by a wedge-caulking mechanism. Each transducer includes an exponentially shaped horn located on each end. The horns of the vertical transducers intersect at the base of the horizontal transducers' horns; the tip ends of the horizontal transducers' horns are used as the driving feet. Longitudinal vibrations are superimposed in the motor and generate elliptical movements at the tip ends of the horns. The working principle of the proposed motor is analyzed. The resonance frequencies of two working modes are tuned to be close to each other by adjusting the structural parameters. Transient analysis is developed to gain the vibration characteristics of the motor. A prototype motor is fabricated and measured. The vibration test results verify the feasibility of the proposed design. Typical output of the prototype is a no-load speed of 928 mm/s and maximum thrust force of 60 N at a voltage of 200 Vrms.

Several multiplexing techniques may be used in next generation GNSS, including QPSK, Interplex, AltBOC, TD-AltBOC, Dual QPSK, POCET. Multiple signals on the same carrier could be multiplexed into a constant-envelope signal with these techniques. Increasing of signals would deteriorate the crossing correlation and its impact on receiving is analyzed. It is shown that cross correlation between signals in-phase has considerable influence; in contrast, the effect could be neglected to signals quadrature. Simulation and real data test is given in the end to support the conclusion, which could guide the selection of multiplex technique and spreading code of Compass.

A linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed, designed, fabricated and tested in a previous study. The longitudinal vibrations of two orthogonal bolt-clamped transducers are superimposed to produce elliptical movements on the driving foot. Firstly, the operating principle of the proposed motor is discussed. The longitudinal and bending vibrations of the transducers are gained by modal analysis. Then, the resonance frequencies and input impendence characteristics of the individual transducers and the motor are calculated respectively to gain the effect from the vibration coupling. The study results state that the vibration coupling between the transducers make their longitudinal resonance frequencies have small increases and the electromechanical coupling factor of the vertical transducer has an obvious decrease after it is linked with the horizontal one. As last, the coupling bending vibrations of the transducers are tested by using a scanning laser Doppler vibrometer.

A new linear ultrasonic motor using the 1st longitudinal and the 4th bending vibration modes of a bolt-clamped type transducer has been proposed and studied. The new motor with two feet employed only the bending PZT elements. Two groups of PZT elements are clamped between the two exponential shape horns and the flange bolt. The driving feet are located in the same side of the transducer. The working principle of the proposed motor are introduced. After the fabrication of a prototype, its admittance characteristics are measured using an impedance analyzer and the vibration modes are tested by a scanning laser Doppler vibrometer. Finally, the mechanical ability of the prototype is tested.

Ultrasonic motors (USM) are new type actuators that exhibit merits such as simple structure, high torque at low speed, compact size, quick response, quiet operation, self-locking when power off, no electromagnetic radiation and higher position accuracy. In the previous study, the authors proposed a new type USM using bending vibration mode. In that new design, elliptical trajectory vibrations are formed on the two driving feet by composing two orthogonal bending vibration modes of a piezoelectric-metal beam, that avoid the mode degeneration problem in the design process. In this paper, our research focuses on the exciting mode of bending vibration ceramics of the proposed motor. Firstly, the vibration characteristics of the proposed motor under different exciting modes by changing the imposed position of the electrode are obtained by transient analysis. Then, the exciting mode is adjusted by changing the imposed area of the electrode, and the vibration strengths of the driving feet are analyzed. Analysis results show that the PZT ceramic away from the neutral plane of the bending mode shape offers more contributions to the bending vibration of the motor under the same exciting voltage, while the PZT ceramic that near to the neutral plane give very few contribution. The study results of this paper can guide the design of general bending vibration transducer.

In a previous study, the authors have proposed, designed and fabricated a cylindrical traveling wave piezoelectric motor excited by a longitudinal and bending hybrid composite transducer. This study focuses the research on the vibration coupling problems of the proposed stator. After the introduction of the working principle of the motor, harmonic analysis is developed to gain the input impedance characteristics of the longitudinal and bending vibration modes of single transducer; the electromechanical coupling factors are calculated to evaluate the energy transfer efficiency. Then, the input impedance characteristics of the two vibration modes of the stator are analyzed to gain the corresponding electromechanical coupling factors. At last, the resonance frequencies of the transducer and cylinder are adjusted to obtain their effects on the electromechanical coupling factors. The study results can guide the design of traveling wave motors that utilized sandwich transducers as actuators.

This paper investigates the hydrodynamic performance of flapping caudal fin by means of numerical simulation. Dynamic simulations of caudal fin with heaving and pitching motion are conducted to determine the relationship between the maximum angle of attack and difference of phase angle in terms of thrust coefficient and propulsive efficiency under low frequency. Combing 20°∼30°maximum angle of attack with 70°∼90°difference of phase angle, outstanding propulsive efficiency can be obtained. In addition, qualitative analyses are made to the wake vortex spacing. This study shows that wake spacing has interaction with the thrust coefficient and the propulsive efficiency.

This paper intends to present and verify a new idea for constructing traveling wave ultrasonic motors that may effectively avoid the drawbacks of conventional traveling wave motors using bonded PZT plates as the exciting elements. In the configuration of the motor's stator, a composite sandwich type transducer is used to excite a traveling wave in a cylinder with two cantilevers as the coupling bridges between the transducer and the cylinder. The design process of the stator is described using the FEM modal analysis method, and the establishment of traveling wave on the cylindrical stator was simulated by FEM transient analysis. To verify the theoretical analysis results, a laser Doppler scanner was employed to test the mode shapes of a prototype stator excited by the longitudinal and bending vibrations respectively. Finally, to validate the design idea, a prototype motor was fabricated and tested; the typical output features are no-load speed of 156 rpm and maximum torque of 0.75 N·m under exciting voltages of 70 V(rms) applied to excite the longitudinal vibration of the transducer and 200 V(rms) applied to excite the bending vibration.

A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 Nm under an exciting voltage of 200 V(rms).

A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 V(rms).

A novel anthocyanidin glycoside, abacopterin J (1), together with the known eruberin B (2) and eruberin C (3) was isolated from the fern Abacopteris penangiana (Hook.) Ching. The structure of the new compound 1 was elucidated on the basis of extensive spectroscopic analysis, including HSQC, HMBC, ((1))H-((1))H COSY and ROESY, and chemical evidence. Abacopterin J is the first example of an anthocyanidin glycoside isolated from natural sources, which is comprised of a flavan and an anthocyanidin moiety.

To avoid the disadvantages of conventional traveling wave ultrasonic motors--lower efficiency PZT working mode of d(31), fragility of the PZT element under strong excitation, fatigue of the adhesive layer under harsh environmental conditions, and low volume of the PZT material in the stator--a new type of traveling wave ultrasonic motor is presented in this paper. Here we implement the stator by nesting 64 PZT stacks in 64 slots specifically cut in a thick metal ring and 64 block springs nested within another 64 slots to produce preloading on the PZT stacks. In this new design, the d33 mode of the PZT is used to excite the flexural vibrations of the stator, and fragility of the PZT ceramics and fatigue of the adhesive layer are no longer an issue. The working principle, FEM simulation, fabrication, and performance measurements of a prototype motor were demonstrated to validate the proposed ideas. Typical output of the prototype motor is no-load speed of 15 rpm and maximum torque of 7.96 N x m. Further improvement will potentially enhance its features by increasing the accuracy in fabrication and adopting appropriate frictional material into the interface between the stator and the rotor.

BACKGROUND: Ultrasonic motors (USM) are based on the concept of driving the rotor by a mechanical vibration excited on the stator via piezoelectric effect. USM exhibit merits such as simple structure, quick response, quiet operation, self-locking when power off, nonelectromagnetic radiation and higher position accuracy. PRINCIPAL FINDINGS: A cylindrical type traveling wave ultrasonic motor using cantilever type composite transducer was proposed in this paper. There are two cantilevers on the outside surface of cylinder, four longitudinal PZT ceramics are set between the cantilevers, and four bending PZT ceramics are set on each outside surface of cantilevers. Two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the cylinder are excited by the composite transducer. In this new design, a single transducer can excite a flexural traveling wave in the cylinder. Thus, elliptical motions are achieved on the teeth. The actuating mechanism of proposed motor was analyzed. The stator was designed with FEM. The two vibration modes of stator were degenerated. Transient analysis was developed to gain the vibration characteristic of stator, and results indicate the motion trajectories of nodes on the teeth are nearly ellipses. CONCLUSIONS: The study results verify the feasibility of the proposed design. The wave excited in the cylinder isn't an ideal traveling wave, and the vibration amplitudes are inconsistent. The distortion of traveling wave is generated by the deformation of bending vibration mode of cylinder, which is caused by the coupling effect between the cylinder and transducer. Analysis results also prove that the objective motions of nodes on the teeth are three-dimensional vibrations. But, the vibration in axial direction is minute compared with the vibrations in circumferential and radial direction. The results of this paper can guide the development of this new type of motor.

A ring type standing wave USM using bending transducer is proposed. The transducer includes one exponential horn located on leading end, and the horn insect with the ring at tip end. The working principle of proposed motor is analyzed. The ring and transducer are designed with FEM The bending vibration modals of ring and transducer are degenerated. Transient analysis is developed to gain the vibration characteristics of stator, and results indicate that the motion trajectories of nodes on the teeth are oblique lines. Results also indicate the proposed design enables the standing wave USM to operate with large vibration amplitude, which would improve the mechanical output characteristics. The results of this paper verify the theoretical feasibility and provide instructions for the development of proposed motor.

A double rings type ultrasonic motor using longitudinal transducers is proposed in this paper. The bending modes of rings are excited by the longitudinal vibration of transducers. Two flexural traveling waves in the two rings, which have the same direction, are excited. The working principle of proposed motor is analyzed. The ring and transducer are designed with FEM. The bending vibration modal of ring and longitudinal vibration modal of transducer are degenerated. Transient analysis is developed to gain the motion trajectories of nodes on the teeth, results indicate that two flexural traveling waves are excited in the two rings. The results of this paper could guide the development of this new type of ultrasonic motor.

A linear ultrasonic motor with rectangle-type stator is proposed in this paper. The stator of proposed motor contains four longitudinal transducers, which are located in rectangle-type. Every transducer includes two exponential shape horns located on each end. And the horns of adjacent transducers intersect at tip ends where located a driving foot. Longitudinal vibrations are superimposed in the motor and generated elliptical trajectories at the driving feet. The working principle of proposed motor is analyzed. The resonant frequencies of two working modals are degenerated by adjusting the structure parameters. The motion trajectories of nodes on the driving feet are gained by transient analysis, results indicate that the motion trajectories of nodes on the four driving feet are ellipses. The vibration amplitudes of driving feet indicate the proposed motor has potential advantage in output characteristics. The results of this paper verify the theoretical feasibility and provide instructions for the development of proposed motor.

A cylindrical ultrasonic motor using bending transducer was proposed in this paper. The stator components of proposed motor contain a cylinder and four bending transducers, and the four uniform bending transducers are set on the exterior surface of cylinder. The bending of transducers is excited by the longitudinal vibration of PZT ceramics. The four transducers are excited with two different groups of signal, and two bending vibrations are generated on the cylinder. When the amplitude of two bending vibrations is equal, and their phase difference on time and space is pi/2, a traveling wave is formed on the cylinder. Thus, an elliptical motion is achieved at the particle on the tooth. And the frictional force between rotor and stator is the driving force to realize the rotation motion of rotor. The PZT ceramics work with d33 mode, which have high electromechanical coupling efficiency and could improve the output characteristics. The working principle of proposed motor was analyzed. The cylinder and transducers were designed with FEM. The sensitive parameters of resonance frequency of transducer and cylinder were gained with modal analysis. The bending resonance frequency of transducers and cylinder were degenerated, and the motion trajectories of nodes on the teeth were analyzed. The result of transient analysis shows that the trajectory of node on the tooth is nearly an ellipse. The results of this paper could be useful in the development of this new type of motor.

A cylindrical standing wave ultrasonic motor using cantilever and sandwich type transducers was proposed in this paper. There are four pairs of cantilevers outside the cylindrical stator, and four PZT ceramics are set between each pair of cantilevers. The PZT ceramics together with a pair of cantilevers compose a longitudinal transducer. The bending mode of cylindrical stator is excited by the longitudinal vibration of PZT ceramics. Thus, linear simple harmonic motions are achieved at the particle on the teeth. And the frictional force between rotor and stator is the driving force to realize the rotational motion of rotor. The PZT ceramics work with d33 mode, which have high electromechanical coupling efficiency and could improve the output characteristics. The working principle of proposed motor was analyzed. The cylinder and longitudinal transducer were designed with FEM. The sensitive parameters of resonant frequency of transducers and cylinder were gained with modal analysis. The longitudinal resonant frequency of transducers and bending resonant frequency of cylinder were degenerated, and the motion trajectories of nodes on the teeth were analyzed. The results of this study could be useful in the development of this new type of ultrasonic motor.

A linear ultrasonic motor using longitudinal and bending (L-B) vibration hybrid Langevin transducer was developed to achieve high output power. The motor consist two exponential shape horns intersected at tip ends where located a single driving foot. L-B vibrations were superimposed in the elastic body of the motor and generated elliptical trajectory at driving foot which can actuate linearly. The sensitivity analysis of structure parameters to the L-B resonant frequencies were performed using finite difference method based on the classical horn theory and flexural horn transfer matrix analysis method, and then degenerated frequencies to 27.476 kHz by choosing the most sensitive parameter. FEM simulation and impedance characteristic test agreed well with the calculated results. The coupling effect between two vibrations was studied and discussed through one phase driving phenomenon. Typical output performances of the prototype were no-load velocity of 1280mm/s and maximum driving force of 45N.

To realize fish-like robot swimming behaviors poses tremendous challenges, especially for the realization of fish body. This paper highlights the system design and experimental research of a free-swimming biomimetic robot fish. By propulsive theories, a design scheme concerning with both physical realization and control methods is presented, where multiple linked robot fish propelled by a flexible body and an oscillating tail fin can be accomplished. The system design of robot fish is decomposed into mechatronic system and motion control system. Underwater experiments are conducted to indicate the parametric relationships. The objectives of this work are to study the propulsive performance concerning with straight-line swimming speed and turning diameter. The experimental results verify that the presented scheme is effective in design and implementation. The performance of the robot fish is determined by the shape parameters and kinematic parameters. This research can instruct the further general design of robot fish.

This paper describes the manufacturing, characterization and parametric modeling of a novel fiber-reinforced composite flexible skin with in-plane negative Poisson’s ratio (auxetic) behavior. The elastic mechanical performance of the auxetic skin is evaluated using a three-dimensional analytical model based on the classical laminate theory (CLT) and Sun’s thick laminate theory. Good agreement is observed between in-plane Poisson’s ratios and Young’s moduli of the composite skin obtained by the theoretical model and the experimental results. A parametric analysis carried out with the validated model shows that significant changes in the in-plane negative Poisson’s ratio can be achieved through different combinations of matrix and fiber materials and stacking sequences. It is also possible to identify fiber-reinforced composite skin configurations with the same in-plane auxeticity but different orthotropic stiffness performance, or the same orthotropic stiffness performance but different in-plane auxeticity. The analysis presented in this work provides useful guidelines to develop and manufacture flexible skins with negative Poisson’s ratio for applications focused on morphing aircraft wing designs. (Some figures may appear in colour only in the online journal)

A rotary piezoelectric actuator using bolt-clamped type transducer with double driving feet is proposed in this study. The first-order longitudinal and fourth-order bending vibration modes are superimposed in the actuator to produce elliptical movements on the driving tips. Longitudinal PZT and bending PZT are clamped between the exponential shape horns and the flange by bolts. The vibration shape changes of the actuator are presented to give a clear explanation of its working principle. Several structural parameters of the exponential shape horn are selected and adjusted to accomplish the tuning process of the longitudinal and bending resonance frequencies. The input impedance and vibration characteristics are calculated by using FEM method; the gained results verify the feasibility of the proposed actuator. After the fabrication of a prototype, its vibration characteristics are measured by using a scanning laser Doppler vibrometer; the tested results are in good agreement with the FEM calculated results. The mechanical output performance experiments state that the prototype achieves a maximum speed of 129 r/min and a maximum torque of 1.5 Nm.

To avoid the disadvantages of conventional traveling wave ultrasonic motors?lower efficiency PZT working mode of d31, fragility of the PZT element under strong excitation, fatigue of the adhesive layer under harsh environmental conditions, and low volume of the PZT material in the stator- a new type of traveling wave ultrasonic motor is presented in this paper. Here we implement the stator by nesting 64 PZT stacks in 64 slots specifically cut in a thick metal ring and 64 block springs nested within another 64 slots to produce preloading on the PZT stacks. In this new design, the d33 mode of the PZT is used to excite the flexural vibrations of the stator, and fragility of the PZT ceramics and fatigue of the adhesive layer are no longer an issue. The working principle, FEM simulation, fabrication, and performance measurements of a prototype motor were demonstrated to validate the proposed ideas. Typical output of the prototype motor is no-load speed of 15 rpm and maximum torque of 7.96 N·m. Further improvement will potentially enhance its features by increasing the accuracy in fabrication and adopting appropriate frictional material into the interface between the stator and the rotor.