Search

The backward motion is an intrinsic feature of the conventional piezoelectric stick-slip actuator (PSSA), limiting the output speed and applications. Various methods have been proposed for restraining the backward motion. Each method has its pros and cons for the practical application of driving a precision motion stage. A novel method for restraining the backward motion is proposed in this article, in which a passive damping foot is utilized to hold the runner when the active driving foot slips on the runner. An actuator is developed based on this mechanism. The structural dimensions of the actuator are determined with an analytic model and a finite element model. A prototype of the proposed actuator is fabricated and tested by experiments. The experiments validate the operating principle of the actuator for restraining the backward motion, which is eliminated (the backward ratio is less than 1%) when the passive damping foot has an appropriate clamping force. The proposed method is very valuable for designing a PSSA with no backward motion, and it can broaden the applications for precision manipulations. [ABSTRACT FROM AUTHOR]

• A piezoelectric actuator combining the direct actuation mode and inertial actuation mode is proposed. • The frequency of the first bending mode reaches 12,720 Hz by using the sandwich structure. • A resolution of 12.5 nm and a maximum scan rate of 190 Hz are achieved by the direct actuation mode. • Maximum speed and thrust of 14.44 μm/s and 1.67 N are achieved by the inertial actuation mode. A piezoelectric actuator operating at direct actuation mode and inertial actuation mode was proposed for linear driving with long stroke, nanometer resolution and high scan rate. Different from the previous piezoelectric actuators constructed with stacked flexure structures, the proposed actuator used a sandwich structure with high resonance frequency. The operating principle was discussed. The structure was designed by the assistance of theoretical analysis and finite element simulation. A prototype was fabricated and its experiments were performed to investigate the characteristics. The resonance frequency of the first horizontal bending mode was measured to be 12,720 Hz by a scanning laser Doppler vibrometer. When operating at the direct mode, a displacement resolution of 12.5 nm was obtained and a maximum scan rate that was about 190 Hz with scan range of 3.685 μm was achieved. When operating at the inertial mode, the prototype achieved the maximum output speed and thrust force of 14.44 μm/s and 1.67 N under the voltage of 420 V p-p and frequency of 15 Hz, respectively. The proposed actuator can achieve a long stroke by the inertial actuation mode and realize high frequency scanning of micron stroke with nanometer resolution by the direct actuation mode, it has good application prospects in the fields of nano scanning and biological manipulation. [ABSTRACT FROM AUTHOR]

A novel stepping piezoelectric actuator is proposed and tested in this work to achieve the linear driving with long stroke and high resolution. The proposed piezoelectric actuator contains four piezoelectric stacks located in U-shape: two of them are set horizontally, whereas the other two are placed vertically. The actuating principle of the U-shaped actuator is analyzed: two piezoelectric stacks are used to control the clamping state of the runner, while the linear stepping motion is achieved by the other two stacks. A double-level screws structure, which not only gives enough preload, but also protects the piezoelectric stacks from lateral forces, is proposed and used to make the piezoelectric stacks work under a reliable condition. An equivalent model is developed for the calculation of the clamping force of the piezoelectric actuator. The equivalent model is based on a concept of converting structures related to clamping forces into springs with certain elastic coefficients. Static analysis is performed by finite element method (FEM) to get the equivalent coefficients of the structures. A prototype is fabricated and the experimental studies are carried out to validate the actuating principle and obtain the mechanical output performances. Experimental results show that the maximum driving force of the prototype is 13.2 N and the maximum velocity is 47.6 μm/s. [ABSTRACT FROM AUTHOR]

Generally, the modal degeneration problem existed in the design of ultrasonic motors using composite vibration modes can be overcome by adopting the same-order orthogonal-bending composite vibrations. The conventional excitation and the modified hybrid one of sandwich type orthogonal-bending composite vibrations with the same order are compared and analyzed in this paper. Compared with the conventional one, the modified hybrid excitation favors that two groups of ceramics exciting two orthogonal-bending modes are placed in the optimum excitation position. Moreover, the modified hybrid excitation can achieve larger vibration amplitude than the conventional one, while the amount of the ceramics adopted and the exciting voltages applied are the same. The first-order orthogonal-bending composite vibrations are chosen to analyze the advantage of the modified hybrid excitation. Finite-element method is adopted to compare the amplitudes of the models with the same sizes but different excitations. The prototypes corresponding to two excitations are fabricated and tested to verify the results of the theory and simulation. It is proved that the modified hybrid excitation can improve the performance of the sandwich type ultrasonic motors using bending composite vibrations. [ABSTRACT FROM PUBLISHER]

A frog-shaped linear piezoelectric actuator was proposed, designed, fabricated, and tested. The proposed actuator only used the first-order longitudinal vibration to generate linear motion, which made the design, optimization, and miniaturization of the actuator more flexible by abbreviating the frequency degeneration. By stimulating the first-order longitudinal vibration, alternate oblique movements are formed on the ends of two driving feet. Meanwhile, an elongating and shortening movement of the whole actuator is generated. When two parallel walls are in contact with the ends of two diving feet and a vertical preload is applied, the vertical components of the alternate oblique movements will overcome the preload, while the horizontal components of the alternate oblique movements and the elongating and shortening movements will together push the actuator into linear motion. Vibration characteristics and alternate oblique movements of the driving feet were investigated by the finite-element method. Experiment tests of vibration characteristics and mechanical output ability were then carried out. The tested resonance frequency and vibration amplitudes agreed well with the calculated ones. The prototype achieved a maximum speed and a thrust of 287 mm/s and 11.8 N, respectively. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

A piezoelectric actuator using the third and fourth bending vibration modes was proposed, designed, fabricated and tested with the aim of accomplishing rotary driving by boltclamped transducer. By superimposing the third and fourth bending vibrations, elliptical movements are formed on the two leading ends of the actuator. When a ring type rotor is in contact with the two diving tips and the vertical preload is applied, the horizontal movements of the driving tips generated by the third bending vibration will push the rotor into motion by frictional forces while the vertical movements produced by the fourth bending vibration will overcome the preload. A method of tuning the resonance frequency of the third bending mode to the fourth bending one was discussed. The horn shape was adjusted to make the two bending modes have nearly uniform frequencies. The vibration characteristic and mechanical ability of a prototype were tested, and the tested resonance frequencies agreed well with the calculated ones. The prototype achieved maximum speed and torque of 86 r/min and 2.5 Nm, respectively. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents and verifies a new idea for constructing rotary ultrasonic motor that may effectively make use of the longitudinal vibrations of the bolt-clamped transducers. Based on the idea of generating elliptical motion on the driving tip by superimposing longitudinal vibrations, a square-type rotary ultrasonic motor with four driving feet is proposed. This new motor consists of four longitudinal vibration transducers, which are located in square-type and form an enclosed construction. The longitudinal vibrations of the four transducers are superimposed to produce the same circular movements on the four feet, which can push the rotor into motion when a preload is applied. By using FEM method, the proposed motor is designed and analyzed, and circular trajectories on the driving feet are gained. The vibration and input impedance characteristics of the motor are measured after the fabricating of a prototype, and the test results are in good agreement with the FEM analysis results. Typical output of the prototype is no-load speed of 71r/min and maximum torque of 12.3Nm at an exciting voltage of 200Vrms. [Copyright &y& Elsevier]

Abstract: A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200Vrms. [Copyright &y& Elsevier]

A cylindrical type traveling wave ultrasonic motor using longitudinal vibration transducers is proposed in this paper. A flexural traveling wave is excited in the cylinder by the longitudinal vibrations of transducers. The working principle of proposed motor is analyzed. The function of flexural traveling wave and motion trajectory of particle on the tooth are developed. The longitudinal resonant frequency of transducer and bending resonant frequency of cylinder are degenerated. A prototype motor is fabricated and measured. Typical output of the prototype is no-load speed of 290r/min and maximum torque of 1.95N·m at a voltage of 200Vrms. [ABSTRACT FROM AUTHOR]

Abstract: A cylindrical type traveling wave ultrasonic motor using longitudinal and bening composite transducer was proposed in this paper. A composite transducer is attached to the cylinder on its outer surface to excite two degenerate flexural vibration modes spatially and temporally orthogonal to each other in the cylinder. In this new design, a single transducer can excite a flexural traveling wave in the cylinder. Two cone type rotors are pressed in contact to the borders of the inner surface of teeth by means of a spring and nut system. The working principle of the motor was analyzed. The resonance frequencies of the two vibration modes of stator were tuned to be close to one another using finite element method. A prototype motor was fabricated and tested. Typical output of the prototype is no-load speed of 281rpm and maximum torque of 1.2Nm at an exciting voltage of 200Vrms. [Copyright &y& Elsevier]

• A two-DOF piezo-driven fast steering mirror is proposed for optical steering. • Two-DOF rotary motions are induced by differential push–pull structure. • The PFSM has high stiffness to avoid being destroyed by lateral force. • The two-DOF PFSM has a good decoupling characteristic. A novel two-DOF piezo-driven fast steering mirror (PFSM) with high stiffness and good decoupling characteristic was proposed. This PFSM could realize rotary motions around X-axis and Y-axis by differential push–pull structure with four piezoelectric stack actuators (PSAs) arranged in cross and orthogonal state, and its lateral stiffness was high enough to overcome the problem that PSA was easy to be destroyed by large lateral force. The PFSM was designed and its working principle was described in detail. The static model was established to analyze the stiffness characteristic of the structure and precisely predict the output angles. The finite element method (FEM) was performed to verify the effectiveness of the proposed structure and static model. A prototype of the PFSM was fabricated, and an experimental setup was established. The experiments showed that the proposed PFSM could achieve rotary motion ranges of 2.33 mrad around X-axis and 2.25 mrad around Y-axis under the voltage of 120 V, respectively. And the resolution was measured as high as 0.28 μrad with the voltage increment of 0.2 V. Furthermore, the first order resonance frequency was measured as 4578 Hz and a good decoupling characteristic was obtained, the coupling errors of both two axes were below 0.75%. The two-DOF PFSM could be applied to the laser communication and the adaptive optics system based on its merits of high stiffness, high resolution and good decoupling characteristic. [ABSTRACT FROM AUTHOR]

• Finite element models considering different knurl tooth angles (KTAs) have been built. • The effect of the KTA on the formation mechanism of the joint is explored. • The average equivalent plastic strain and temperature increase by 30.1% and 28.1%. • The maximum stress is reduced by 48.3% when KTA is increased from 110° to 140°. • It is suggested to select KTA as large as possible. Ultrasonic welding (USW) has been receiving more and more attentions in material joining field due to its advantages of cleanness and high efficiency. The knurl tooth angle (KTA), as a key factor of horn knurl geometry (HKG), has significant influences on the contact and friction behavior of the joint formation. Although there have been some researches on the simulation of ultrasonic welding, the 3D finite element (FE) model considering the influence of KTA has not been reported. In this study, the FE models of different KTAs are established to reveal the effects of KTA on joint formation. The simulation result shows that the KTA greatly influences the process parameters of the USW after 0.025 s. The gaps of the faying interface and local stress concentration in the sonotrode-workpiece contact area, caused by KTAs less than 120°, are the main reasons for the strength reduction of the joint. The higher average equivalent plastic strain and temperature of the welding area, formed by KTAs greater than 130°, are turned out to be the main reasons for the formation of more bonds. The simulation has been verified by experiments, and the results provide guidance to improve the quality of the joint. [ABSTRACT FROM AUTHOR]

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 Vrms applied to excite the longitudinal vibration of the transducer and 200 Vrms applied to excite the bending vibration. [ABSTRACT FROM AUTHOR]

An electromechanical coupling model of a bending vibration type piezoelectric ultrasonic transducer is proposed. The transducer is a Langevin type transducer which is composed of an exponential horn, four groups of PZT ceramics and a back beam. The exponential horn can focus the vibration energy, and can enlarge vibration amplitude and velocity efficiently. A bending vibration model of the transducer is first constructed, and subsequently an electromechanical coupling model is constructed based on the vibration model. In order to obtain the most suitable excitation position of the PZT ceramics, the effective electromechanical coupling coefficient is optimized by means of the quadratic interpolation method. When the effective electromechanical coupling coefficient reaches the peak value of 42.59%, the optimal excitation position ( L 1 = 22.52 mm) is found. The FEM method and the experimental method are used to validate the developed analytical model. Two groups of the FEM model (the Group A center bolt is not considered, and but the Group B center bolt is considered) are constructed and separately compared with the analytical model and the experimental model. Four prototype transducers around the peak value are fabricated and tested to validate the analytical model. A scanning laser Doppler vibrometer is employed to test the bending vibration shape and resonance frequency. Finally, the electromechanical coupling coefficient is tested indirectly through an impedance analyzer. Comparisons of the analytical results, FEM results and experiment results are presented, and the results show good agreement. [ABSTRACT FROM AUTHOR]

• A multi-DOF ultrasonic motor using a piezoelectric spherical shell stator is proposed. • This structure is beneficial to realize high symmetry and miniaturization. • The proposed motor can rotate the rotor around X, Y and Z axes, respectively. • A prototype is fabricated to verify the working principles, designs and simulations. • The proposed motor has merits of compact size and high velocity. A novel spherical stator multi-DOF ultrasonic motor using in-plane non-axisymmetric mode was proposed. The stator and the rotor of the motor adopt a piezoelectric ceramic spherical shell and two metal hemispherical shells, respectively, which is beneficial to realize high symmetry and miniaturization of the whole motor. The motor adopts the pair combination of three orthogonal in-plane non-axisymmetric modes to generate three types of elliptical motions at eight driving feet, which can rotate the rotor around X, Y and Z axes, respectively. Finite element method was used in the design of the proposed motor including searching for reasonable modes by modal analysis and verifying the uniform driving of the eight driving feet by transient analysis. A prototype was fabricated to verify the working principles, designs and simulations. The mechanical output characteristics around X, Y and Z axes were measured under different excitations, pre-tightening forces and loading conditions. The no-load rotary velocities of the prototype were 200 r/min, 198 r/min and 250 r/min and the maximum load torques were 10.8 mN·m, 11.0 mN·m and 12.3 mN·m around X, Y and Z axes, respectively. The spherical stator multi-DOF ultrasonic motor could be applied to robot visual driving systems as its merits of compact size and high velocity. [ABSTRACT FROM AUTHOR]

• A linear standing-wave USM with a hollowed and symmetrical stator is proposed. • The hollow stator can guide the mover, simplifies the guide and preload mechanism. • The motor can realize bi-directional motions by same order vibrations of the stator. • The motor realizes speeds of 30.86 mm/s and 32.31 mm/s in the two-way motions. • The motor realizes resolutions of 0.5 μm and 0.7 μm in the two-way motions. A linear standing-wave ultrasonic motor with a hollowed and symmetrical stator is proposed in this study. The stator is cut from a cuboid block to produce a hollow and symmetrical structure, in which four thin-walled beams are formed on each end of the stator. Four driving feet are circumferentially installed at each end of the stator to guide the movement of the mover, and this design can simplify the guide rail and preload mechanism, which is beneficial to realize further miniaturization. Besides, the bi-directional motions are separately achieved by only using one sine signal to excite the same order vibration of the two groups of the thin-walled beams, which is conducive to the characteristic consistency of the bi-directional motions. Then, the finite element method is used to determine the parameters of the motor, the prototype is fabricated, and the output characteristics are tested. The experimental results show that the maximum no-load velocity, resolution, and maximum carrying load of the prototype in the forward motion were 30.86 mm/s, 0.5 μm and 39 mN, respectively; while that in the backward motion were 32.31 mm/s, 0.7 μm and 33 mN, respectively. This work sheds a new light on the design of the linear bi-directional standing-wave ultrasonic motors, simplifying the guide rail and preload mechanism and utilizing only one signal and the same order vibration to realize the bi-directional motions. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel miniature piezoelectric robot (MPR) was designed and proposed in this work, in which a unique structural feature is that the robot base is only obtained through a single cuboid block, having good simplicity and compactness. Besides, unlike the slow-fast periodic horizontal deformation of the inertial unit in traditional inertial impact mode, three unconventional (diagonal, jumping, resonant) inertial impact modes (DIIM, JIIM, and RIIM) based on the unique structure of the robot were proposed to achieve the performance improvement in both resolution, single step value, and motion speed. The three working principles were analyzed, and the main geometric parameters were determined by the cooperation of the established model and the finite element method. Then, a robot prototype with a size of 20 mm × 12 mm × 9 mm and a weight of 4.7 g was manufactured, and the motion performance was tested, in which the robot was powered by an external power supply by wires. The results showed that the robot could achieve both high resolution, large single step, and high motion speed successfully by cooperating the three inertial impact modes, including a highest resolution of 0.5 µm under DIIM, a maximum single step of 63.1 µm under JIIM, and a fastest speed of 24.8 mm/s under RIIM. The coordination of these performance could well expand the application scope of MPRs. [Display omitted] • A miniature piezoelectric robot features by a compact cuboid is proposed. • Three unconventional inertial impact modes are combined for improving performance. • The robot achieves a high resolution of 0.5 µm under diagonal inertial impact mode. • The robot can realize a large step of 63.1 µm under jumping inertial impact mode. • The robot runs at a high speed of 24.8 mm/s under resonant inertial impact mode. [ABSTRACT FROM AUTHOR]

A novel two-degree-of-freedom (2-DOF) micro scratching platform driven by inchworm type piezoelectric actuator with parallel mechanisms is proposed, designed, fabricated, and tested aiming for accomplishing cross-scale plane trajectory tracking. Through the hybrid compliant notch parallelogram flexure hinges (HCNPs), the actuation mechanism can realize output decoupling and parasitic displacement limitation simultaneously, which is of great importance to improve the positioning precision. The structural stiffness and maximum stress are analyzed through theoretical modeling and finite element modeling of HCNPs. The symmetric operating mode of parallel actuator accomplishes plane motion using only six driving and clamping elements, and the trajectory tracking control strategy is completed based on it. The results indicate that the scratching platform can implement 2-DOF decoupled motion with a travel range of 40 × 40 mm2, and the minimum step distance is 0.78 µm. The precise planar synthesis is also accomplished and the open-loop trajectory synthesis errors are lower than 2.87 %. Besides, the triangular and circular trajectories with depth of 1 µm are one-step scratched successfully due to the high horizontal payload capacity up to 41.5 N. Moreover, the platform has potential to be used in probe tip-based micro scratching for other planar trajectories. [Display omitted] • An inchworm type micro scratching platform with parallel mechanisms is developed. • Micro scratching platform achieves trajectory tracking without principal errors. • Micro scratching platform implements 2-DOF decoupled motion with high capacity. • Planar trajectories with depth of 1 µm are one-step scratched successfully. [ABSTRACT FROM AUTHOR]

A ultrasonic motor (USM) has been developed to meet the specific demands for compact actuators, which can drive humanoid eyeball to realize multi-degree-of-freedom (MDOF) motions. This USM has a ring shape composite stator, and employs combinations of axial bending mode and in-plane nonaxisymmetric mode to generate three type ellipses at four driving feet, pushing the spherical rotor to rotate around x , y and z axes respectively. FEM was used in the design process, including tuning the mode frequencies by sensitivity analysis, as well as optimizing the stator dimensions by transient simulations, where the shapes and attitude angles of the driving ellipses were retracted and analyzed with the deduced method, together with the driving effects comparison of two feasible exciting methods, achieving uniform driving behavior among the four feet. A prototype has been fabricated to verify the working principles, designs and simulations. The mechanical performance around x , y and z axis were measured under different electrical excitements and preload conditions, and typical stall torque is 17.5 mN m and the no-load speed of 82 r/min in x, y rotation, meanwhile stall torque is 12.5 mN m and the maximum speed of 43 r/min in z rotation, which meet the presented requirements. [ABSTRACT FROM AUTHOR]

A new type of multiple-degree-of-freedom (multi-DOF) ultrasonic motor was developed aiming at high output torque and compact structure. To reach this purpose, a ring type composite stator was proposed with four driving feet uniformly arranged in the inner circumference of the ring stator. The stator employs two orthogonal axial bending modes and a radial bending mode, by exciting two of them simultaneously, to generate elliptic trajectories on driving feet tips and to push sphere rotor around x , y and z axis respectively. Based on the deduced criteria, a specific combination of the A(0, 5) axial bending modes and R(0, 2) radial bending mode were chosen to realize that the rotating directions of the elliptical driving trajectories on four feet tips can push the sphere rotor to spin in the same direction consistently, thus the efficiency and output performance will be improved by decreasing the slip between feet and rotor. FEM was used to design the motor including selecting key parameters to tune the resonant frequencies by sensitivity analysis, and a prototype was fabricated and tested. The experiment results showed that the maximum output torque of the motor is 0.118 N m and the maximum speed is 55 r/min. [ABSTRACT FROM AUTHOR]

This paper presents a new-type linear ultrasonic motor which takes advantage of the combination of two orthogonal bending vibration modes. The proposed ultrasonic motor consists of eight pieces of PZT ceramic plates and a metal beam that includes two cone-shaped horns and a cylindrical driving foot. The finite element analyses were finished to verify the working principle of the proposed motor. The mode shapes of the motor were obtained by modal analysis; the elliptical trajectories of nodes on the driving foot were obtained by time-domain analysis. Based on the analyses, a prototype of the proposed motor was fabricated and measured. The mechanical output characteristics were obtained by experiments. The maximal velocity of the proposed motor is 735 mm/s and the maximal thrust is 1.1 N. [ABSTRACT FROM AUTHOR]

• A 2-DOF piezoelectric platform is developed to achieve the cross-scale motion. • A piezoelectric actuator with 3-dimensional motions is designed to drive the rotor. • The cross-scale motions are achieved by combining stick-slip and stick-stick modes. • A special active friction switching approach is utilized to change working modes. • The platform can realize a motion range of 2π rad and a resolution of 23.03 μrad. In order to overcome the typical cross-scale motion contradiction between the large motion range (radian scale) and high displacement resolution (microradian scale) in single actuation device, we proposed a novel two degrees of freedom (2-DOF) piezoelectric rotary platform (PERP) to implement cross-scale rotary motions based on active friction switching. A longitudinal-bending-bending (LBB) piezoelectric actuator (PEA) was developed to realize 2D lateral bending motions and 1D longitudinal motion. The former was used to drive rotor, while the latter was employed to implement friction switching. The principles of the PERP and the switching mechanism of the working modes were illustrated systematically. The finite element method (FEM) was utilized to simulate the motions of the PEA, and a series of experimental results successfully verified the principles and the theoretical analyses. The 2-DOF cross-scale rotary motions were successfully realized, and the PERP can achieve large motion range of 2π rad, maximum rotary velocity of 817.88 mrad/s, high resolution of 23.03 μrad and low coupling motion of 4.91%. The proposed friction switching method held benefits to improve flexibility and stable frequency range (more than 10 times) of dynamic scanning motion. The developed PERP could be used to drive optical mirrors with merits of both large motion range and high resolution for multiple target tasks. [Display omitted] [ABSTRACT FROM AUTHOR]

• A method of generating 8-shaped trajectory of the driving tip was presented. • The two-dimensional trajectory was generated by a single-phase exciting signal. • The prototype obtained almost identical forward/backward output characteristics. • A maximum speed of 1373 rpm was achieved under a pre-load of 9N. A novel bending-bending piezoelectric actuator driven by a single-phase signal is proposed, in which the two-dimensional 8-shaped trajectory of the driving tip moves the runner. The exciting signal is a mixture of two sinusoidal signals with a frequency ratio of 1:2. The moving direction of the runner can be reversed by changing the phase shift between the higher frequency and the lower frequency components of the exciting signal. The actuator is designed and its modal frequencies are analyzed by the finite element method (FEM) to obtain the 8-shaped trajectory of the driving tip under the exciting signal. The vibration characteristics of the actuator and the trajectory of the driving tip are measured after fabricating a prototype. The operating principle of the actuator is verified and the mechanical performances of the prototype are evaluated. The prototype can rotate a pulley (22 mm in diameter) at the maximum speeds of 1373 rpm and 1350 rpm forward and backward under a preload of 9N, respectively. [ABSTRACT FROM AUTHOR]

This paper proposed a new piezoelectric actuator operating in two working modes: the resonance working mode under alternating current (AC) signals and the non-resonance working mode under direct current (DC) signals. The AC resonance working mode used the hybrid of two resonance bending vibrations to produce high speed and large stroke linear motion, whereas the DC non-resonance working mode used the static horizontal bending movements to achieve linear driving with micrometer stroke and nanometer resolution. The working mechanism of the actuator was illustrated; then finite element analysis (FEA) method was utilized to finish the design and analyses; at last a prototype was manufactured to measure the performance. Under the resonance working mode, the proposed actuator achieved maximum output speed of 1750 mm/s and the maximum output thrust of 30 N under 500 V p-p . Also, when working under the DC non-resonance working mode, the maximum output displacement was 2.62 µm. And the measurable minimum output displacement was 50 nm, which can reach smaller in theory. The correlation coefficient between the output displacement and the input DC voltage is 0.998, which was good for the control of the actuator under the non-resonance working mode. This piezoelectric actuator can accomplish linear position quickly and accurately in a large stroke with simple structure using bending modes. [ABSTRACT FROM AUTHOR]