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This research presents the development and evaluation of a miniature autonomous robot inspired by insect locomotion, capable of bidirectional movement. The robot incorporates two piezoelectric bimorph resonators, 3D-printed legs, an electronic power circuit, and a battery-operated microcontroller. Each piezoelectric motor features ceramic plates measuring 15 × 1.5 × 0.6 m m 3 and weighing 0.1 g, with an optimized electrode layout. The bimorphs vibrate at two flexural modes with resonant frequencies of approximately 70 and 100 kHz. The strategic placement of the 3D-printed legs converts out-of-plane motion into effective forward or backward propulsion, depending on the vibration mode. A differential drive configuration, using the two parallel piezoelectric motors and calibrated excitation signals from the microcontroller, allows for arbitrary path navigation. The fully assembled robot measures 29 × 17 × 18 m m 3 and weighs 7.4 g. The robot was tested on a glass surface, reaching a maximum speed of 70 mm/s and a rotational speed of up to 190 deg./s, with power consumption of 50 mW, a cost of transport of 10, and an estimated continuous operation time of approximately 6.7 h. The robot successfully followed pre-programmed paths, demonstrating its precise control and agility in navigating complex environments, marking a significant advancement in insect-scale autonomous robotics. [ABSTRACT FROM AUTHOR]

This article introduces a method of enhancing the energy conversion efficiency of a traveling wave rotary ultrasonic motor with a flexible rotor by increasing the friction coefficient at the stator–rotor interface. The increased friction coefficient leads to improvements in energy conversion efficiency by increasing the output power and reducing friction loss power. Experimental verification showed that the friction coefficient in the interface increased from 0.21 to 0.32, the maximum energy conversion efficiency increased from 36.8% to 46.3%, and the interface friction loss was reduced. [ABSTRACT FROM AUTHOR]

In this paper, a composite excitation method is used to optimize the design of an existing cantilevered cylindrical ultrasonic motor to avoid vibration interference. Modal and transient simulation analysis of the stator structure was carried out by the finite element method. Optimized stator structure is simpler than the original motor. Simulation analysis results show that the circumferential amplitude is increased by more than 35% with 55.7% reduction in ceramic usage. [ABSTRACT FROM AUTHOR]

Impedance matching circuits are capable of tuning and wave filtering, which is beneficial to performance improvement of piezoelectric ultrasonic motors. At present, impedance matching for piezoelectric ultrasonic motors is usually realized through a series inductance, which has the problem of poor wave filtering effect. Different from the previous series inductance matching method for ultrasonic motors, a series inductance and capacitance matching method is proposed for a radial standing wave piezoelectric ultrasonic motor. The series capacitance is added to adjust the quality factor of the resonance tank so that a desired wave filtering effect can be obtained. The values of the series inductance and capacitance are derived based on the Butterworth–Van Dyke model of the piezoelectric ultrasonic motor. Simulations are conducted to verify the feasibility of the proposed matching method. Finally, the waveforms of voltages and currents as well as torque–speed curves of the motor are measured. The results validate the proposed matching method. In addition, the previous series inductance matching method is compared. The results show that the proposed series inductance and capacitance matching method not only achieves tuning function but also obtains a significantly improved wave filtering effect. Moreover, the torque–speed characteristics of the motor are also improved with the proposed matching method. [ABSTRACT FROM AUTHOR]

To fulfill high-reliability requirements for aerospace applications, a novel traveling wave rotary ultrasonic motor with a piezoelectric backup function (Backup motor) is proposed in this paper. The backup function is enabled by the addition of a set of piezoelectric ceramics (PZT). Based on the ultrasonic motor of the CSX-60, a cantilever-tooth backup motor (CTBM) is designed and fabricated. This backup motor can operate in three working modes according to the excitation settings of PZTs, namely normal mode, backup mode, and enhanced mode. The relationships between three working modes' performances are analyzed by finite element (FE) analysis and prototype tests. The results show that backup mode, as the substitution, can nearly reach normal mode's performance, while enhanced mode is obviously higher than others. Furthermore, a modified backup motor with straight-tooth (STBM) and different sizes of PZT is designed and tested as a supplement to verify the feasibility of the proposal. In addition, the effect of stress reduction on PZT damage is verified by extreme working experiments. The comparison between the two types of motors indicates that STBM can provide better frictional drive performance. This proposal can provide a new reference for the subsequent reliability study of ultrasonic motors. [ABSTRACT FROM AUTHOR]

This paper proposed a double-sided staggered conical teeth traveling wave rotating ultrasonic motor based on in-plane bending mode, which reduces the difficulty of rotor preload application and improves the output characteristics of in-plane bending mode traveling wave rotating ultrasonic motor. The motor has four sets of drive teeth alternately distributed on both the inner and outer sides of the vibrator, with the drive teeth gap dedicated to accommodate the piezoelectric ceramic piece, and the staggered drive teeth on both sides of the vibrator are used to drive the rotor rotation. The motor operates in two in-plane third-order bending modes with the same frequency and orthogonal to each other, and is excited by four sets of piezoelectric ceramic disks spaced 90 degrees apart from the inner and outer sides. After the prototype was completed, its vibration characteristics and output performance were experimentally tested, and the actual effects of the three excitation schemes were compared. The experimental results show that the motor can provide a maximum output torque of 1.82N-mm and a maximum no-load speed of 96.4 rpm when the excitation voltage is 300 V and the excitation frequency is 20.60 kHz. [ABSTRACT FROM AUTHOR]

In order to facilitate the widespread application of ultrasonic motors, it is essential to conduct a quantitative study aimed at enhancing their performance. The present paper provides a comprehensive theoretical analysis of an ultrasonic motor equipped with dual vibrators, enabling operation in both the single-driven and dual-driven modes, thereby enhancing versatility in terms of performance adjustment. This study provides a detailed examination of the motor's unique performance characteristics and its varying output responses to different driving signals. Experimental investigations are conducted in both the single-driven and dual-driven modes to validate theoretical predictions. The results demonstrate that the motor exhibits a maximum speed, torque, and power that are 1.59, 1.28, and 1.62 times higher than those of the single-driven stator, respectively. A conclusion can be drawn that the motor will attain the desired performance when operated in the appropriate driven mode. [ABSTRACT FROM AUTHOR]

In order to improve the output torque of an in-plane bending mode traveling wave rotary ultrasonic motor, a double-sided tapered teeth traveling wave rotary ultrasonic motor was proposed. The motor is designed with three types of adaptive rotors that can be used for replacement in different output environments. Simulation analysis was conducted using ANSYS, and prototype production and experimental testing were conducted. The experimental results show that when the excitation voltage is 300 V and the excitation frequency is 22.665 kHz, the maximum output torque that the motor provide is 3.087 N·mm, and the maximum no-load speed is 295 rpm. [ABSTRACT FROM AUTHOR]

In order to simplify the motor structure, to reduce the difficulty of rotor pre-pressure application and to obtain better output performance, a new internal cone type rotating traveling wave ultrasonic motor is proposed. The parametric model of the internal cone type ultrasonic motor was established by the ANSYS finite element software. The ultrasonic motor consists of an internal cone type vibrator and a tapered rotor. The dynamic analysis of the motor vibrator is carried out, and two in-plane third-order bending modes with the same frequency and orthogonality are selected as the working modes. The other advantages of this motor are that pre-pressure can be imposed by the weight of the rotor. The prototype was trial-manufactured and experimentally tested for its vibration characteristics and output performance. When the excitation frequency is 22260.0 Hz, the pre-pressure is 0.1 N and the peak-to-peak excitation voltage is 300 V, the maximum output torque of the prototype is 1.06 N·mm, and the maximum no-load speed can reach 441.2 rpm. The optimal pre-pressure force under different loads is studied, and the influence of the pre-pressure force on the mechanical properties of the ultrasonic motor is analyzed. It is instructive in the practical application of this ultrasonic motor. [ABSTRACT FROM AUTHOR]

For a traveling wave rotary ultrasonic motor, matching the stator with a proper flexible rotor can be challenging because of the actual contact mechanism's complexity. Due to the lack of effective evaluation and prediction means in the rotor design process, the prototype test is usually needed to truly measure how well it performs, leading to high cost and long design cycle. In order to solve this problem, an efficient performance evaluation method of the flexible rotor based on equivalent contact pressure is proposed. By the key parameters of the flexible rotor's contact surface (area and pressure), an equivalent pressure model of the contact surface is established, which reveals the influence law of the flexible rotor's structural parameters on the motor's output performance. It is doubly verified by dynamics simulation and experiments. The advantage of this method is that without dynamics computation and prototype test, only statics analysis can evaluate the matching score of flexible rotor and target stator quickly and accurately. This study is expected to provide support for the structure design and performance prediction of the traveling wave rotary ultrasonic motor's rotor, in which significant time and cost savings can be achieved. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a new type of circular ring traveling wave linear ultrasonic motor with incomplete teeth. The motor's movable slider is pressed against the end face of the tooth structure on the outer surface of the circular ring vibrator under a certain pre-pressure, four piezoelectric ceramic plates are evenly distributed at 90° intervals on the inner side of the circular structure, and four sets of driving teeth are arranged at 45° intervals from the position of the piezoelectric ceramic plates.When the motor is in operation, only one driving tooth works, and the life of the ultrasonic motor can be increased by rotating the different working teeth. The motor operates in two in-plane third-order bending modes that are orthogonal to each other at the same frequency. The dynamic design and simulation of the vibrator was carried out using ANSYS finite element software to analyze the effect of the structure on the mode. The principle prototype was fabricated, and the operating mode of the vibrator was measured using a laser Doppler vibrometer (LDV), and the vibration characteristics and output performance of the prototype were tested. Experimental results show that the motor runs smoothly at the excitation voltage of 240 V peak-to-peak, the excitation frequency of 30.459 kHz and the pre-pressure of 0.6 N, with the maximum output force of 90 mN and the motor no-load speed of 102 mm/s. [ABSTRACT FROM AUTHOR]

Traveling wave rotary ultrasonic motors (TRUMs) are widely used in various industrial processes due to their attractive features, such as compact structure, high accuracy, and fast response. However, the major limiting factors of the operational performance of TRUMs under high-voltage excitation are the nonlinear behavior caused by the nonlinearities of the piezoelectric materials and the friction between the stator and rotor of the motor. In this study, a nonlinear dynamics model and an identification method are presented to directly design the driver circuit for suppressing the nonlinear behavior under high voltage excitation. Firstly, by studying the time–frequency characteristics of the isolated electrode voltage, a single-sided Hertzian contact forced oscillator model of TRUMs is established, involving the nonlinearities of the piezoelectric material and friction. Secondly, a harmonic balance nonlinear identification is proposed in the time domain for TRUMs. The influence of the voltage and preload on the nonlinear phenomena is discussed. Lastly, a novel driver circuit is proposed to suppress the nonlinearities using feedback from the isolated electrode. Experiments showed that the total harmonic distortion decreased by 89.4% under 500 Vpp. The proposed drive circuit design method is used to find a high excitation voltage and preload to achieve greater motor output power. [ABSTRACT FROM AUTHOR]

• A cross-level vibration prediction method is proposed for the transmission mechanism of the USM stator under electron radiation, characterizing the variations from material properties to component characteristics and verified by the experiment of different electron fluences. • The cross-scale degradation model is established to explore the cross-scale material property changes. • An edge-based smoothed finite element method (ES-FEM) is developed for the vibration analysis of the USM stator, achieving superior accuracy and efficiency. Moving components exposed to electron radiation over longer durations are more prone to failure due to its complex changes from material properties to component characteristics. It involves multi-scale analysis, leading to current methods being deficient in accuracy and efficiency. In this paper, a cross-level vibration prediction method, which selects the ultrasonic motor (USM) stator as a typical component for Jupiter exploration, is proposed by incorporating the cross-scale changes of material properties based on the edge-based smoothed finite element method (ES-FEM). A cross-scale degradation model for exploring the material properties is constructed by establishing the correlation between the degradation of molecular chains and the mechanical properties of the epoxy resin. The ES-FEM is developed for investigating the vibration of the USM stator, by introducing the edge-based gradient smoothing technique (GST) to perform the strain smoothing operation in its stiffness matrix, offering superior accuracy and efficiency. The experiment of 1.2 MeV electron radiation under different electron fluences was carried out. It demonstrated that the present method can achieve higher accuracy and efficiency than the traditional one, while being closed to the experimental results with the frequency and amplitude errors of 0.03 % and 1.3 %, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this letter, a millimeter scale thick film rotating traveling wave ultrasonic motor based on chemical mechanical thinning and polishing process was proposed. The 30 $\mu \text{m}$ thick piezoelectric functional layer is fabricated to realize good compactness and high piezoelectric properties. The thickness and diameter of the stator are about 240 $\mu \text{m}$ and 4 mm, respectively. The vibration mode of the motor is B02 mode under the resonant frequency of 26.2 kHz. The motor can achieve stable bidirectional rotation under the excitation of four sinusoidal voltages. Moreover, when the excitation voltage is 50 $\text{V}_{\text {pp}}$ , the maximum speed can reach 766 rpm under the preload force of 686 $\mu \text{N}$. [ABSTRACT FROM AUTHOR]

In-plane bending traveling wave ultrasonic motors (USM), which are compact in structure and flexible in design, have been widely applied in biological engineering, optical engineering, and aerospace engineering. However, the high driving voltage and complicated driving circuit of this kind of USM restrict their further miniaturization and electromechanical integration in these applications and bring some potential safety hazards. To solve this problem, a low-voltage-driving traveling wave USM incorporating cofired multilayer piezoelectric ceramics was proposed in this work. Four cofired piezoelectric ceramics were strategically designed to excite two orthogonal third-order in-plane bending modes with the same frequency of the USM. The principles of traveling wave synthesis and low-voltage-driving of the USM were deduced, and the stator dynamic design and transient dynamic simulation were carried out by finite-element method. The microproperties of cofired piezoelectric multilayer ceramics, the vibration characteristics of the stator, and the mechanical output performance of the USM were tested by experiments. The results indicated that the motor can work as low as 5 $\text{V}_{\text {p-p}}$. A long stroke with a maximum forward and reverse rotational speeds of 187.7 and 176.6 r/min were obtained, respectively, and a maximum stalling torque of 4.8 mN $\cdot$ m at 47.3 kHz under 15 $\text{V}_{\text {p-p}}$ was achieved. The results showed that the proposed USM is small, low in driving voltage, and high in torque output, which has promising applications in aerospace, biomedicine, and other fields that require a lightweight and integration of driving devices. [ABSTRACT FROM AUTHOR]

To overcome the problem of frequency consistency and simplify the design process of linear ultrasonic motor, a novel traveling wave linear ultrasonic motor with a ring-type stator is proposed in this paper. The combination of two orthogonal bending vibration modes with the same order is selected as the operating mode of the motor. A traveling wave along the side of the stator is utilized to drive the slider to move linearly. The stator adopts a ring symmetrical structure, which can effectively ensure that the resonance frequencies of the two vibration modes are consistent. Thus, we do not need to tune the frequencies of the two vibrations by constantly adjusting the shape of the stator or designing complex clamping parts to fix the stator without making any influence on the vibrations. Meanwhile, a three-dimensional finite element model of the motor is built. Using the model, we obtain the elliptical motion trajectories of the stator driving surface, the output performance of the motor, the sticking-slipping-separation contact characteristic between the stator and the slider and fabricate and measure a prototype of the proposed motor. [ABSTRACT FROM AUTHOR]

A novel standing wave linear ultrasonic motor with double driving feet based on longitudinal-bending coupling mode is designed in this study. The motor adopts the bonded-type structure, and four pieces of piezoelectric ceramics on a metal beam are divided into two groups. Two voltages with 90° phase difference are applied to two groups of Pb-based lanthanumdoped zirconate titanates ceramics, respectively. Then the first longitudinal and second bending modes generated are superimposed on the stator, which can produce elliptical motion trajectories on the driving feet. The excitation method and driving mechanism of the motor are illustrated in detail. A finite model of the stator is established in the ANSYS parametric design language interface, and the operating mode of the stator and motion trajectories on the driving feet are discussed. The prototype is fabricated, and its impedance characteristics and mechanical output performance are tested. The results show that the maximal no-load velocity of the motor is ∼147.78 mm/s under a voltage of 200 V and a preload of 3 N. The maximum thrust force is ∼1.1 N when the voltage and preload are 200 V and 6 N, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the requirement that the speed of rotor speed of ultrasonic motor can be stabilized quickly, combined with the mathematical model of two-phase traveling wave ultrasonic motor, we designed the rotor speed stability control strategy of the two-phase traveling wave ultrasonic motor based on voltage and current double feedback. We simulated, analyzed, and verified the designed strategy using Matlab/Simulink simulation tool. The rationality of the simulation results proves the correctness of the designed control strategy, which lays a theoretical foundation for the production design of two-phase traveling wave ultrasonic motor. [ABSTRACT FROM AUTHOR]

To improve positioning precision of the traveling wave ultrasonic motor (USM), a flexible shaft was used, and the structure was redesigned to reduce the fluctuations of step angles and speed. The start and stop response performances of the motor were analyzed theoretically and tested by a high-resolution test rig. The step characteristics were calculated, which showed the minimum step angle is below 0.20″ under different torques. The positioning process included two modes: continuous mode and step mode. In continuous mode, the speed of the motor was controlled by PID control based on the tests of frequency-speed characteristic of the motor. In step mode, the step characteristics of the motor was tested under different load torques and applied different lengths of driving voltage to find the minimum of step angle. From the tests, the step angle increases rapidly with the periods of driving voltage and the single-step angle fluctuations of the motor with flexible shaft is much less than that of motor with normal shaft. Finally, the positioning performances of USM were tested. The results showed that the minimum positioning error of the motor with flexible shaft could achieve 0.37″ (1.79 μrad) and the time costed was below 1 s. • A flexible shaft was used to improve positioning precision of the ultrasonic motor. • Step performance of the USM was utilized to a certain limit, which was below 1.0″. • The minimum positioning error of the USM with flexible shaft could achieve 0.37″. • Positioning accuracy of the USM can reach sub-arc seconds under different torques. [ABSTRACT FROM AUTHOR]

Ultrasonic motors can be driven by burst voltage to obtain micro-stepping motion, and the corresponding step size depends on the load and cycle number of the applied ac driving voltage in one burst. The rotor of the motor achieves a step motion through a process of startup-acceleration–deceleration-stop. To obtain a large torque (or thrust force) and quick startup, a large vibration amplitude of a stator and a high growth rate are desired; thus, a large mechanical quality factor and a high electromechanical coupling factor are required. However, the stator vibration decays for a long time before it stops because of low mechanical energy loss; meanwhile, the rotor moves a big step. Hence, there is contradiction between thrust force and resolution/response time. This paper presents a new drive method to improve the step resolution and response time while keeping the torque by damping control. By simply adding a switch and a shunting damp circuit and connecting the shunting circuit to ultrasonic motors at the end of a drive burst signal, the stator vibration attenuates more rapidly and the step size is reduced. First, the damping effect of the piezoelectric system with a passive resonant shunting circuit (a resistor and an inductor connected in series) on the free stator of a bar-type rotary traveling wave ultrasonic motor has been tested. Next, a drive circuit comprising electronic switches and the shunting circuit is designed and utilized for measuring the performance of the motor. Experimental results have well proven the proposed method. [ABSTRACT FROM AUTHOR]

In order to improve the output performance of the rotating traveling wave ultrasonic motor and study the optimal pre-pressures under different loads, the theoretical calculation and experimental verification on a TRUM-70H ultrasonic motor were carried out. The dynamic model of an ultrasonic motor is established, and the influence of pre-pressure on the mechanical properties of the ultrasonic motor is analyzed. Taking the TRUM-70H ultrasonic motor as the object of study, the relationship between the optimum pre-pressure and the load torque is analyzed. A multi-functional testing platform for an ultrasonic motor is built to verify the theoretical derivation results, and the reason for the error is also pointed out. According to the conclusion, the pre-pressure should be selected according to the load when the ultrasonic motors are assembled. The results show that there is a coupling relationship between the pre-pressure and the load torque on the speed of the ultrasonic motor. In the effective working range of the ultrasonic motor, the optimum pre-pressure is approximately linearly positively correlated with the load torque. When the pre-pressure is set according to the actual load demand during assembly, the output efficiency of the ultrasonic motor can be improved. [ABSTRACT FROM AUTHOR]

This paper presents a multi-parameter model of an ultrasonic motor for speed control. Firstly, the model is divided into the steady-state part and the dynamic part, and then the speed mapping relationship of amplitude, frequency, phase difference is described by linear function, exponential function, and hyperbolic tangent function, respectively in steady-state modeling. The least-square transfer function identification is used in the dynamic velocity modeling. This paper also constructs a modeling flowchart from the discrete models to the state-space function based on the pairwise combination of parameters, which can realize the flexible control of different parameters. Finally, the error box diagram of the model and the comparison between the measured results and simulation ones both verify the effectiveness of the model. [ABSTRACT FROM AUTHOR]

A novel hollow type of traveling wave rotary ultrasonic motor is proposed, optimized, fabricated, and tested in this study. Unlike conventional ultrasonic motors, this novel ultrasonic motor adopts a bran-new preloading method that preload is applied from the bottom of the stator through a wave spring, which can not only enhance the anti-overload ability but also extend the working life of the motor. According to this motor, a three-dimensional finite element model has been built by the commercial finite element software ADINA. In terms of the friction material and the preload, a detailed further optimization procedure is given after the initial design. Finally, the appropriate size and location of the friction layer and a proper preload for this motor have been determined. Almost all of the motor's mechanical capacities, such as rotational speed, torque, and deformation, can be obtained by simulations in ADINA, which have good agreement with experimental results. [ABSTRACT FROM AUTHOR]

This study fabricated textures on the stator surface of a traveling wave ultrasonic motor (USM) using laser and investigated the tribological behavior of a polytetrafluoroethylene (PTFE) composite friction material and stator. Initially, the effect of textures with different densities was tested. As the results suggested, the generation of large transfer films of PTFE composite was prevented by laser surface texturing, and adhesive wear reduced notably despite the insignificant decrease in load capacity and efficiency. Next, the 100-h test was performed to further study the effects of texture. Worn surface and wear debris were observed to discuss wear mechanisms. After 100 h, the form of wear debris changed into particles. The wear mechanisms of friction material sliding against the textured stator were small size fatigue and slight abrasive wear. The wear height of friction material decreased from 3.8 μm to 1.1 μm. This research provides a method to reduce the wear of friction materials used in travelling wave USMs. [ABSTRACT FROM AUTHOR]

Nowadays, piezoelectric actuators are widely used, but are rarely applied in high overload environments due to th difficulty implementing them. Traveling wave rotary ultrasonic motors (TRUMs) have the characteristics of variable structure and are insensitive to overload, endowing them with the potential ability of high overload resistance. In this study, four TRUMs with different rotor structures are designed to work under the high-impact acceleration of 10,000 g through modifying the rotors with a designed slotted disc spring. The dynamics model is established, the impact process is simulated, and the results are analyzed successively. The high-impact test, deformation measurement and performance test of the motors are carried out to verify the modification. The results show that performance of the TRUMs with a disc spring declines much less than those without a disc spring after the high-impact test. The TRUM-4 with the modified rotor and disc spring has the best performance, the speed of which decreased only 1.6% at the torque of 0.15 N m, and it is considered to be capable of withstanding the high acceleration of 10,000 g. This work is significance for guiding the ultrasonic motors' optimization to expand their application in high-overload environments. [ABSTRACT FROM AUTHOR]

By analyzing the contact mechanism between the stator and rotor, this study demonstrates that the prepressure on the rotor is not a constant value because of the structural stiffness of the preload structure. In addition, this study explains the driving mechanism of the traveling wave ultrasonic motor under unsteady prepressure and deduces a dynamic model considering the structural stiffness of the preload structure. Furthermore, the relationship between the speed characteristics of the motor and the structural stiffness of the preload structure is obtained through model simulation. The simulation results are found to be in good agreement with the experimental results, which demonstrates the correctness of the dynamic model. Moreover, the output characteristics of the motor can be improved by designing an appropriate structural stiffness of the preload structure. [ABSTRACT FROM AUTHOR]

Featured Application: An impedance control method is proposed for a designed traveling wave ultrasonic motor with a spherical rotor to achieve more precise force control, which can potentially be applied to a multi-degree-of-freedom haptics device. A traveling wave ultrasonic motor (TWUM) with a spherical rotor was designed and fabricated for a haptic interface. The mechanical characteristics testbed was set up to test the performance of the motor under the modulation of frequency and phase difference, as well as for conducting haptic interaction, and the phase difference modulation based on certain frequency was adopted as the driving mode for the proposed motor. Due to the complexity and uncertainty of the contact mechanics of the stator and rotor, the direct torque control effect of the TWUM is not ideal for the force feedback. In this paper, the impedance control method was adopted to realize the force interaction based on positional proportional–integral–derivative (PID) control. The virtual linear spring and virtual wall experiments are conducted to verify the effect of the proposed method. Results show that the position-based impedance control method has a better effect than direct torque control for the haptic interaction based on an ultrasonic motor (USM). [ABSTRACT FROM AUTHOR]

To realize applications involving low speed and high torque in the high-performance actuator industry, especially in the aerospace field, we propose a novel 70H traveling wave rotary ultrasonic motor (TRUM) with an outer diameter of 70 mm and an aperture ratio of 53% (the ratio between the aperture and outer diameter). The power transmission mechanism between the stator and the rotor is analyzed, and a method for realizing low-speed–high-torque characteristics of TRUMs is proposed. ANSYS software is used to simulate the modal parameters of the stator, and the ratio β between the normal amplitude and the tangential vibration velocity of the stator is proposed. The larger the value of β, the lower the speed and the higher the torque. Furthermore, two prototype motors are fabricated, namely, 70HA and 70HB. Compared with 70HA, the maximum no-load speed of the improved 70HB (50 rpm) is decreased by 23.1% and the maximum stall torque (2.4 N∙m) is increased by 100%. Besides this, with a smaller mass of 210 g and a higher torque density of 11.43 N∙m/kg, 70HB has fundamentally different mechanical characteristics. [ABSTRACT FROM AUTHOR]

A novel parametric contact model and the corresponding parametric identification procedure for speed prediction and control of a well-known standing wave linear ultrasonic motor L1B2 USM under different input voltages and loads is proposed, which is based on a combination strategy of analytical modeling and identification modeling. In the physical frame, a refined interface friction model is established and the distinctive position-dependent nonlinearity of the LUSM is investigated. By implementing decoupling and step-by-step modeling for subsystems, the input voltage region parameter estimations are conducted. • A combination strategy of identification modeling and analytical modeling is employed to study the contact mechanism of L1B2 USM to predict the steady-state output speed for precision speed control of the motor. • The distinctive position-dependent nonlinear characteristic of the LUSM is investigated and evaluated, and the effect of region of input voltage amplitude on contact dynamics is considered in the model. • A new interface friction model is established to overcome the drawbacks and limitations of the existing Coulomb model in describing the stick-slip motion at interface. • An integrated Ether CAT servo controller is developed for the prototype of L1B2 USM actuated motion platform. Linear ultrasonic motor is a complicated electromechanical coupling system, precision speed control of which is a challenge for the researchers for difficulties in obtaining its accurate speed prediction model. The stator/slider contact mechanism, which can be described by a stick-slip-separation dynamics, greatly affects the output speed. Considering that practically the full physics of the system is often inaccessible to be modeled accurately for lack of prior knowledge of some physical/structural parameters, this paper presents a novel parametric contact model and the corresponding parametric identification procedure for steady-state speed prediction of a typical standing wave linear ultrasonic motor utilizing longitudinal and bending modes. Compared with the training data-driven general modeling, the approach retains physical insight into some important nonlinear characteristics in the contact process to improve prediction performance. The dynamic equations of the stator are deduced by using Timoshenko beam theory and Hamilton's principle and a new interface friction model including asperity contact based stick friction and normal ultrasonic oscillation related slip friction is developed. Besides, the distinctive feature of position-dependent nonlinearity of linear ultrasonic motor, which can be characterized by variation of the vibration of the stator at interface, is evaluated by introducing a variable named nominal axial force of the stator. In the study, this variable acts as the output of an embedded model in the contact model, parameters and structure of which are to be identified. Further, the effect of the region of input voltage on the contact behavior, is taken into account in the identification. In order to collect the input/output data for the identification procedure, an effective and synchronous data acquisition and transmission hardware/software experimental system is established. By employing off-line maximum likelihood estimation method, the input-voltage-region based parameters can be obtained. It is validated credibility of the speed prediction model under different loads and different input voltages with a prototype of linear ultrasonic motor actuated motion platform. [ABSTRACT FROM AUTHOR]

This figure showed the improvement of the energy transfer efficiency of USM by designing new types of polyimide composite and surface texture. • The new polyimide composite as frictional materials of USM was designed. • USM with PI composites had higher energy transfer efficiency that that with PTFE composites. • Fabricating micro-dimples on the surface of PI composites can further improve the efficiency of USM. • Processing the same surface texture on the stator made a reverse effect on the transfer efficiency of USM. In order to improve the transfer efficiency of the travelling wave ultrasonic motor (TRUM), the advanced polyimide-based (PI) frictional materials with high friction coefficient and elastic modulus were designed and prepared by hot press sintering. The friction coefficient of PI composite sliding against phosphor bronze was investigated by a flat-on-flat pattern tribo-meter simulated the running conditions of the TRUM. Besides, the micro-dimples with diameter of 300 μm and area density of 7.06% were fabricated on the surface of PI composites by laser ablation. The friction coefficient of the textured PI interface further increased compared to the smooth PI or polytetrafluoroethylene (PTFE) interface. Therefore, the mechanical output torque, rotational speed and transfer efficiency of the TURM with new frictional materials and surface texture were correspondingly improved. The enhancement mechanisms were discussed by analyzing the changes in friction coefficient and contact sate of the tribo-pairs. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The focus of this paper is to propose a contact model of a radial standing wave ultrasonic motor in order to evaluate the motor performance accurately. The contact behavior between the stator and rotor is characterized by test and a continuous contact on the contact interface is confirmed. A contact model describing the continuous contact is then developed with analytical method. The stator vibration, the force transmission between the stator and rotor, and the output of the motor are analyzed. The impacts of different vibration amplitudes and structural parameters on the performances of the motor are evaluated based on the proposed model. Finally, a test platform for measuring the performance of the motor is built and torque-speed curves of the motor under different voltages are measured. The accuracy of the contact model is verified by comparison between measurement and calculation results. The proposed model not only can be used for design and optimization of the radial standing wave ultrasonic motor but also offers insight into the contact mechanics of standing wave ultrasonic motors. [ABSTRACT FROM AUTHOR]

Highlights • Establishing a complete 3D FE model to study the TRUMs. • It can help to know the motor's mechanical capacity before prototype manufacture. • The actual contact mechanism between stator and rotor is reflected accurately. • Torsional deformation of the rotor during rotation can be obtained. • Simulations can facilitate the stress analyses to avoid the failure of USMs. • Providing a powerful tool for structure design and performance prediction of USMs. Abstract To evaluate the response and output performance of an assembled and complete ultrasonic motor, a 3D finite element model has been proposed by a commercial finite element software ADINA. The simulated results of the output performance can be obtained, which are in good agreement with the available experimental data. Therefore, it is convenient to know the mechanical capacity of the motor before prototype manufacture. Moreover, the radial, circumferential and axial displacements of the contact nodes are acquired to simulate the real elliptical motions of the stator. Without assuming that the rotor behaves as a rigid body, the actual contact mechanism between the stator and rotor is reflected accurately. The simulation shows the distinct stress concentration issue of the motor, which can facilitate the stress analyses to avoid the failure of the motor. This study provides a powerful tool for the structure design and performance prediction of the ultrasonic motor. [ABSTRACT FROM AUTHOR]

This article deals with the mathematical–analytical model of a radially polarised stator, part of a piezoelectric travelling wave ultrasonic motor based on the shear effect. The stator is treated with a Reissner–Mindlin plate model containing piezoelectric terms. The so-obtained mathematical description of the disc stator takes into account its geometry, kinematics and characteristics that influence efficiency and torque. Rayleigh–Ritz discretisation is used to obtain eigenfrequencies and eigenmodes of the stator plate. In addition, there are often teeth over the contact surface of ring-shaped stators to minimise the friction losses during operation of the motor, and possible vibration modes are compared with respect to the deflexion of the contact points. In the laboratory, measured eigenfrequencies of the free vibrations of the plate corroborate the numerical method. Particularly, the generation of travelling waves requests the excitation of two degenerated vibration modes in a certain electrode configuration. A voltage inverter was designed for this purpose. [ABSTRACT FROM AUTHOR]

Heat loss occurs in the process of energy conversion, which causes the temperature rise and performance degradation of ultrasonic motor. In this article, a novel theoretical model is developed to investigate the temperature field and output characteristics of a standing wave ultrasonic motor. The roughness of contact surface and the interaction between temperature rise and material parameters of stator are taken into account in the proposed model. The frequency–temperature characteristics of stator are studied, and the changes in the dielectric coefficients of piezoelectric materials with respect to the temperature are determined by experimental data. The accuracy and effectiveness of the developed model are validated by correlative experiment. The results show that the developed model can not only predict the temperature variation of motor in continuous operation but also evaluate the influence of surface roughness and various input parameters on output characteristics of motor. These researches will give useful guidelines for optimizing heat source and enhancing reliability of motor. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For application in control moment gyros, we considered a hollow traveling wave ultrasonic motor with a diameter of 70 mm. The effective electromechanical coupling coefficient (EMCC) of the stator was determined. The influence of the vibration mode of the stator and the structural dimensions of the metal elastomer and piezoelectric ceramic ring on the effective EMCC was investigated. According to the FEM simulation results, four different stators were manufactured and tested. The EMCC obtained through the simulations was greater than the measured values, with the lowest simulated and measured values being 17.202% and 16.431%, respectively, and the highest simulated and measured values being 28.452% and 26.780%, respectively. The relative errors between the simulated and measured values were all less than 10%. This work will help us to improve the output efficiency of the motor. [ABSTRACT FROM AUTHOR]

The authors are developing multi degree of freedom micro spherical ultrasonic motor using wire stator for vascular endoscope. Spherical ultrasonic motor with 20 times model is used to confirm the driving characteristics as experimental equipment. Wire stator is designed by assuming the introduction to a vascular endoscope and transient response analysis is performed by the finite element method compared with 20 times model. In this study, the authors improve new support structure on waveguide and investigate new influence of the attenuation of the traveling wave transmitted on the wire stator by analyzing and changing the condition of the model. In the future, the authors will measure the amplitude of the wire stator by experiment and verify the accuracy of the simulation. [ABSTRACT FROM AUTHOR]

It is crucial to study the problem of traveling wave distortion due to its severe effect on the stability and efficiency of traveling wave ultrasonic motors (TWUM). In this study, the anisotropic elasticity as a new factor causing the traveling wave distortion in MEMS TWUM was considered, and an electromechanical model considering the effect of anisotropic elasticity was established to evaluate the distorted traveling wave. Initially, the orthogonal modes of the stator were investigated using finite element simulation, and the orthogonal modes' two defects induced by the anisotropic elasticity were observed, which included modal splitting and shape distortion. Subsequently, the electromechanical model was established based on the defective orthogonal modes using Hamilton's principle and classical laminated plate theory. Additionally, the effect of modal splitting and shape distortion on the traveling wave distortion was investigated based on the electromechanical model. It demonstrated that B 13 was the optimal orthogonal mode for the high-quality traveling wave. Finally, MEMS TWUMs were fabricated and tested to verify the theoretical results. The test results were obtained using a laser Doppler vibrometer, and it was observed that the traveling wave produced from B 13 was optimal. The test results of rotational speed measured using a high-speed camera also verified that B 13 was the optimal orthogonal mode for the traveling waves. [ABSTRACT FROM AUTHOR]

• A surface contact model of ring type traveling wave ultrasonic motors is proposed. • The circular three-dimensional contact and friction problem is described. • The flexibility of the rotor is taken into account in the proposed model. • The normal contact and tangential friction mechanisms between the stator and rotor are investigated. • Experimental results validate the accuracy of the proposed model. A surface contact model of ring type traveling wave ultrasonic motors is proposed in this paper in order to describe the circular three-dimensional contact and friction problem between the stator and rotor accurately. Differing from previous contact models of traveling wave ultrasonic motors, the flexibility of the rotor, which results in the irregular shape of contact area and inhomogeneous distribution of contact pressure along radial direction, is taken into account in the proposed model. The normal contact between the stator and rotor is analyzed with finite element method and the tangential force transmission on the contact surface is investigated with analytical method. The contact pressures and the tangential stresses on the contact surface are obtained. Mechanical performances of the motor are also studied based upon the proposed model. Finally, torque-speed curves of a prototype motor are measured and compared with the calculated results of the proposed model, and good agreements are obtained. In addition, the proposed surface contact model is compared with previous line contact models. It is found that the calculated results of the surface contact model are closer to measured results than those of line contact models. The comparison results verify the accuracy of the proposed surface contact model. [ABSTRACT FROM AUTHOR]

A cylindrical traveling wave ultrasonic motor using bonded-type composite beam is proposed in this work. In this new design, a new exciting mode for L-B (longitudinal-bending) hybrid vibrations using bonded-type is adopted, which requires only two pieces of PZT ceramic plates and a single metal beam. In the new motor, the traveling wave of a cylinder can be excited by the L-B vibrations of a bonded-type beam. When two alternating voltages with phase difference are applied, the longitudinal and bending vibrations of the beam can be generated synchronously based on the new exciting mode for L-B hybrid vibrations, and the temporal phase difference of the two vibrations is always 90°. Finite element method is adopted to realize the modal degeneration in order to confirm the final structural parameters of the motor, and analyze the motion trajectory of the driving tip. After the fabrication of a prototype, the vibration characteristics and mechanical output ability are measured. The maximum no-load speed and maximum output torque of the prototype are 342 rpm and 6.26 mN m at a voltage of 100 V rms . [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this research is to present a new design of standing-wave ultrasonic motor. This motor uses three piezoelectric actuating blocks which deform appropriately when powered up. The deformations of the blocks in ultrasonic range are internally amplified via the design of the motor by about 80 times and collectively yield an elliptical trajectory for the driving head of the motor. Finite Element Analysis using ANSYS was performed for both dynamic analysis and optimization of a prototype motor. The numerical results verified that at steady state, the motor can achieve vibrations in micro-meter level and the velocity can reach decimeter scale, satisfying the fast speed requirement as a positioning actuator. [Copyright &y& Elsevier]

• Mechanism of energy conversion efficiency improvement with flexible rotors studied. • 3D finite element model with coupling among various parameters established. • Transient solution and modal analysis methods applied on TRUM-60. • Results and validated experimentally as well as using 3D vibration measurements. Flexible rotors are widely used in traveling wave rotary ultrasonic motors (TRUMs) because of their higher energy conversion efficiency; however, there have been few reports on how flexible rotors improve the energy conversion efficiency of ultrasonic motors. In this study, we investigate the improvement mechanism of energy conversion efficiency in TRUMs with flexible rotors. A 3D finite element (FE) model with full coupling among a piezoelectric coupled stator, rotor, friction layer, and the rigid–elastic contact interface of the stator and friction layer is established. To analyze the mechanism by which the efficiency of the TRUM is improved, the contact interface and rotor vibration information are extracted. Taking TRUM-60 as an example, the transient solution method and modal analysis method are used to solve the model. It is found that when the stator mode is B 09 , the flexible rotor mode is B 19. The energy conversion efficiency of the TRUM is obtained from the ratio of output power to the electrical input power of the model solution. The results are validated using 3D vibration measurements and energy conversion efficiency experiments. The simulation result shows that the motor with flexible rotor improves the energy conversion efficiency compared with the motor with rigid rotor, which can be attributed to two reasons: first, the axial amplitude ratio of the flexible rotor to the stator is reduced; second, the flexible rotor reduces the radial friction. This study reveals the influence of flexible rotor on the output efficiency and can thus provide guidance for rotor design. [ABSTRACT FROM AUTHOR]

This paper presents the sensitivity analysis of an ultrasonic linear motor using design of experiments (DOE) and the finite element (FE) optimization of its deformation amplitude. A first ultrasonic linear motor prototype has been built at the laboratory. A deformation amplitude of about 6.6 ,im can be obtained by applying a 100 V voltage. The goal is to obtain a bigger deformation amplitude by varying the motor parameters, in particular the vibratory piece dimensions. First of all, a parametrization of the motor structure is carried out. Then, with the aim of reducing the variation ranges of the input parameters—but also to avoid performing a large number of simulations—a preoptimization stage is necessary. Thus, sensitivity analysis is carried out using design of experiments, which is a good way to obtain the influence of the input parameters on the objective function. Factorial designs have been chosen to find out the effects of each input factor but also the effect of their interactions. This method then is compared with Doehlert design technique, which is generally used for optimization approaches. The results show that it is absolutely necessary to take into account the quadratic terms in the model because they represent an important effect. The use of design of experiments revealed to be an interesting way to analyze numerically the ultrasonic motor as a pre-optimization stage and already allows one to improve the deformation amplitude but also to reduce the input parameter variation ranges. Different FE optimization methods are then applied, and results show that the deformation amplitude can be increased by a factor higher than 10 compared to the initial design. [ABSTRACT FROM AUTHOR]