Traveling Wave Ultrasonic Motor Research Articles

A cylindrical traveling wave ultrasonic motor using bonded-type composite beam

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 342rpm and 6.26mNm at a voltage of 100Vrms.

Increasing the efficiency of traveling wave ultrasonic motor by modifying the stator geometry

Current traveling wave ultrasonic motor (TWUSM) utilizes comb-teeth structure as deflection amplifier. The position of the stator neutral axis to the stator contact surface is one of the factors that influences the deflection amplifier. Stator deflection directly effects on motor performance. In this study, the modification of the comb-teeth stator design is proposed to see its effect on motor efficiency. The modification is done so that the neutral axis position is further distance from the stator top contact surface. The proposed solution is to remove a selected mass element from the comb-teeth structure. Modeling, simulation and experimental work of the proposed concept is carried out utilizing Shinsei USR60 as the chosen TWUSM. The modeling and analyses are conducted through multi-physic finite element simulation MSC Marc Mentat. The results of the analyses and experimental work reveal that the modified comb-teeth stator increases the position of the neutral axis from the stator top surface. Due to the neutral axis shifting, the results also confirm that the proposed modified motor has higher efficiency compared to the non-modified motor.

Wear properties of brass and PTFE–matrix composite in traveling wave ultrasonic motors

The wear of a traveling wave ultrasonic motor has certain particularities due to its special drive mechanism. In this investigation, the progression of wear of a brass stator against a PTFE–matrix composite friction material is reported. During 200h of operation, the performances of an ultrasonic motor and the properties of its friction surfaces were examined. Different wear stages were observed. Surface topography and debris characteristics were analyzed to assess the wear mechanisms that operate in different wear stages. Under the imposed operating conditions the running-in wear stage requires 80h. In early period of running-in wear stage, adhesive wear is the main wear mechanism of the friction material. The debris forms a multi-layered, agglomerate sheet. In the second part of the running-in period, the main wear mechanisms change to delamination wear and adhesive wear. The debris piles up as small particles. In the steady wear stage, the main wear mechanism is delamination wear result from fatigue. The debris forms small flake-like sheet but they are rare. Abrasive wear exist in all stages of wear. By contrast, the main wear mechanism of the brass stator is abrasive wear.

Dynamic analysis of an ultrasonic motor using point contact model

We propose the dynamic modeling of a traveling wave ultrasonic motor using a point contact model between the stator and rotor. This model can simply and accurately estimate the transient response of the rotor motion. In this paper, we model the dynamic behavior of the motor torque and angular velocity based on the vibration amplitude of the elliptical motion generated in the ultrasonic motor. The use of a recent high-speed camera with a high-power lens (high-speed microscope) enables the observation of elliptical motion and the measurement of vibration amplitudes. We build a synchronous motor drive system including the high-speed microscope and verify the model experimentally. The proposed model has been in good agreement with the experimental results.

Dual piezoelectric beam robot: The effect of piezoelectric patches’ positions

Inspired from linear traveling wave ultrasonic motors, a dual piezoelectric beam robot is presented. It consists of an aluminum beam structure, with two non-collocated piezoelectric patches bonded on its surface. The aim of this article is to study the effect of the piezoelectric patches’ positions on the performance of the robot. For a given robot dimension, a finite element model developed in a previous work for the robot structure is verified experimentally here and then used to determine the optimal piezoelectric patches’ position. It has been found that locating the piezoelectric patches near the ends of the beam will lead to best performance, and that the traveling wave is mainly generated between the two patches. Two prototypes have been manufactured for this aim and have shown good agreement with simulation results.

Millimeter-Scale Traveling Wave Rotary Ultrasonic Motors

Bidirectional rotary motion of a millimeter-scale traveling wave ultrasonic motor is demonstrated using solution-deposited thin-film lead zirconate titanate and wafer-scale microelectromechanical system fabrication techniques. Rotation speeds of a motor 3 mm in diameter have been characterized up to 2000 r/min as a function of voltage, phase, and frequency, with power consumption less than 4 mW. Frequency characterization shows no nonlinear behavior, while phase characterization shows that motion can be generated with a single source drive. Furthermore, imprint in the piezoelectric response was exploited to achieve higher speeds, starting voltages lower than 4 V, and demonstration of a 2-mm diameter motor up to 1730 r/min. Design and fabrication of the motors are also presented.

Continuous high-performance drive of rotary traveling-wave ultrasonic motor with water cooling

It is known that rotary traveling-wave ultrasonic motors (RTUSMs) have several inherent advantages over conventional electromagnetic motors. However, the practical applications of RTUSMs are limited in the field of transitory servo drive. The underlying reason is that the temperature rise caused by internal losses has a significant influence on the motor characteristics, which gives rise to substantial performance degradation and poor operational reliability. To explore the feasibility of RTUSMs in the applications of continuous motion drive, we propose to maintain the output performance by directly suppressing the working temperature rise. Based on convective heat transfer, a water-cooling motor base was designed to remove heat from the stator. The motor base was fabricated by embedding a simple pipeline structure and connected to a commercial PC water-cooling radiator. The experimental results show that the RTUSM60 motor maintains an output power of 3.3W and a temperature rise of 22°C during 48-h continuous operation with water cooling. Due to the effective suppression of temperature rise, the motor can work with a stable output power of 2.35W even under the load torque of 0.9Nm.

Temperature evaluation of traveling-wave ultrasonic motor considering interaction between temperature rise and motor parameters

In this paper, a novel model for evaluating the temperature of traveling-wave ultrasonic motor (TWUSM) is developed. The proposed model, where the interaction between the temperature rise and motor parameters is considered, differs from the previous reported models with constant parameters. In this model, losses and temperature rises of the motor were evaluated based on the temperature-related varying parameters: the feedback voltage Vaux of the stator, dielectric permittivity ɛ and dielectric loss factor tanδ. At each new temperature, Vaux, ɛ and tanδ were updated. The feasibility and effectiveness of this proposed model was verified by comparing the predicted temperatures with the measured one. The effects of driving voltage, driving frequency and ambient temperature on the predicted temperature were also analyzed. The results show that the proposed model has more accurate predicted temperature than that with constant parameters. This will be very useful for the optimal design, reducing the heat loss, improvement of control and reliability life of TWUSM.

Survey of a contact model and characteristic analysis method for a travelling wave ultrasonic motor

The important research area associated with the Ultra-Sonic Motor (USM) is the contact problem between the stator and the rotor. Because the USM operates by the friction force between the rotor and the stator, the contact problem of the USM have to be taken into account to analyze the motor performance accurately. Consequently, various types of the analysis methods have been proposed based on a contact model which describes the complex nonlinear contact condition of the USM. In this paper, diverse types of contact analysis methods for a Travelling Wave Ultra-Sonic Motor (TWUSM) are clearly condensed and precisely examined. The governing equations for the analysis of the TWUSM performance are derived through a precise investigation of the relationship between the contact condition and the motor performance in this paper. Furthermore, the motor performance is analyzed using contact models and the calculated data are compared with the experimental results.

Dynamic analysis of a short cylinder piezo motor

The bar-type traveling wave ultrasonic motor is simple, inexpensive, easy to use, and suitable for miniaturization. Its operating performance is significantly affected by the dynamic behavior of the vibrator. In this work, the analytical equations for calculating the dynamic behavior of the motor vibrator are presented using the ring model. The natural frequencies and vibrating modes of the motor are investigated using the analytical equations. Changes in the natural frequencies along with the motor parameters are analyzed. The forced responses of the vibrator to two input signals with a phase difference of 90° are given. A FEM analysis in ANSYS is used to simulate the natural frequencies and vibrating modes of the vibrator. A test is conducted to illustrate the analytical calculative results.

Three-dimensional finite element analysis of interfacial delamination in traveling wave ultrasonic motors

Ultrasonic motors (USMs) are novel electric motors used for positioning controls. Due to the drive characteristic of USMs, wear and fatigue of friction material at the contact friction interface are inevitable. Contact deformation can cause local damage of USMs. Therefore, obtaining the details of the stress distribution due to the inelastic deformation is important. In this paper, a contact model of traveling wave ultrasonic motor (TWUSM) is proposed. A three-dimensional finite element model with cohesive zone elements embedded between friction layer and rotor is then developed. Infinite finite elements are included in this modeling as the boundary condition. The evolution of deformation in friction layer and rotor due to the mechanical surface loading is presented. The possible interfacial delamination process between friction material and rotor is also numerically investigated.

Modal analysis of a stator of Double Rotor Traveling Wave Rotary Ultrasonic Motor (DTRUM) (Single Degree of Freedom)

This paper outlined the modal analysis of a Double Rotor Bar-type Rotary Traveling Wave Ultrasonic Motor (DBTRUM) with single degree of freedom (SDOF). The first bending vibration mode generated from the inverse piezoelectric effect produces traveling wave in the stator, the traveling wave generated in the stator is converted to rotary motion on the two rotors by the use of friction layer between the rotor and the stator surfaces. The system was first designed theoretically after which it was then simulated with finite element method software (ANSYS) to obtain the modal frequency and mode shape.

Ring-type traveling wave ultrasonic motor using a radial bending mode [Correspondence

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.

Self-Tuning Fuzzy Speed Controller Of Travelling Wave Ultrasonic Motor

Abstract Aiming at the nonlinear characteristic of ultrasonic motor, some control strategies have been proposed to control the rotating speed of ultrasonic motor. But most of these strategies are too complex to realize using a low-cost embedded device. In this paper, a simple fuzzy speed controller is designed for ultrasonic motor. Until now, there has no mature and theoretic design method of fuzzy controller. Therefore, experience of expert is often used as the base of design. It makes the design of fuzzy controller become a sophisticated task. In this paper, the design method of fuzzy controller based on fuzzy model is described in detail. Rules of the fuzzy controller are optimized offline using ant colony optimization, and the appropriate parameters of fuzzy controller are also ascertained during the process of optimization. The designed controller is used to control the rotating speed of traveling wave ultrasonic motor with the type of USR60. According to the difference between the actual responses with different speed References, a kind of online tuning method is proposed to modulate the proportional coefficient of fuzzy control. Experiments indicate the validity of the proposed fuzzy controller.

Digital Position Control Strategy of Traveling-wave Ultrasonic Motors

Since a conventional controller is continuous one, control period is normally set for a long time. When applying that controller for a travelling-wave ultrasonic motor whose parameters and performance are time-varying as a result of increasing temperature and operating condition, it is consequently resulted in degradation of the control performance. In this paper, a digital control algorithm is proposed for position control of the motors to shorten the long control period to maintain the stability of the motor performance. The proposed controller is digitally implemented by a SH7125 microcomputer utilizing a high-performance embedded workshop. The state quantities such as acceleration, speed and position, which are necessary for digital implementation, are provided by a rotary encoder. However, the optical encoder causes quantization errors in the speed information. To overcome the problem, a digital Variable Structure System (VSS) observer is also included to estimate the state quantities. The control input will be calculated after comparing the measured values and the estimated values given by the VSS observer. In short, a small, low cost and fast responsive digital controller is designed, based on a digital VSS observer, by using the SH7125 microcomputer. Effectiveness and reliability of the proposed digital controller are experimentally verified.

Characteristic Analysis of an Traveling Wave Ultrasonic Motor using a Cylindrical Dynamic Contact Model

The traveling wave ultra-sonic motor (TWUSM) is operated through the frictional force between the rotor and the stator. Hence, the contact mechanism should be analyzed to estimate the motor performance. However, the nonlinearity of the contact mechanism of the TWUSM makes it difficult to propose a proper contact model and a characteristic analysis method. To address these problems, a novel contact model is proposed and be termed the cylindrical dynamic contact model (CDCM) in this research. An estimation method of the motor performance is proposed using the CDCM, an analytical method, and a numerical method. The feasibility and usefulness of the proposed characteristic analysis are verified through experimental data.

Characteristic model of travelling wave ultrasonic motor

In general, the design and analysis of ultrasonic motor and motor’s control strategy are based on mathematical model. The academic model is widely used in the analysis of traveling wave ultrasonic motor (TWUSM). But the dispersive characteristic of piezoelectric ceramics and other complicated process, such as the friction, make the model’s precision not so accurate. On the other hand, identification modeling method, which is built based on the tested data, has obtained increasing application in the study of ultrasonic motor’s control technology. Based on the identification model, many control strategies can be designed easily. But the identification model is an approximate model, so if a more accurate model of ultrasonic motor can be obtained, the analysis and design of motor control system will be more effective. Characteristic model is a kind of identification model which can accurately describe the characteristics of TWUSM. Based on the tested data, this paper proposes the modeling method of ultrasonic motor’s characteristic model. The paper also makes a comparison of the effectiveness of different identification algorithms. Aiming at the speed control of ultrasonic motor, the influence of the parameter’s initial values on the precision of model is discussed. The calculating results indicate the availability of this characteristic model.

Characteristic analysis and shape optimal design of a ring-type traveling wave ultrasonic motor

The contact mechanism should be analyzed for an estimation of the performance of a traveling wave ultra-sonic motor (TWUSM), because the operation of this type of motor depends on the frictional force between the rotor and the stator. However, the nonlinearity of the contact mechanism of the TWUSM makes it difficult to proposed a proper contact model, a characteristic analysis method and an optimal design method. To address these problems, a characteristic analysis and optimal design method using a cylindrical dynamic contact model (CDCM), an analytical method, a numerical method and an evolutionary strategy algorithm (ESA) is proposed in this research. The feasibility and usefulness of the proposed characteristic analysis and optimal design method are verified through experimental data. Furthermore, the importance of the shape of the teeth and the reason for the improvement of motor performances by the chamfering at the teeth are proposed and verified in this paper.

Modeling of Rotary Traveling Wave Ultrasonic Motor

Comparedwith traditional electromagnetic motor, the ultrasonic motor (USM) exhibits unique performance advantages. To speed up the research and development of thedriving ASIC for a rotary travelingwave type ultrasonic motor in diameter of 45mm, it is necessaryto obtain its motor model. The modeling of USM which is composed of two parameters (resistance andcapacitance) is presentedand explained. Both the modeling and simulation are based on our real tested motor-drivercharacteristic data by PSIM software. The testeddata can be reproducedby adjusting the unknown two parameters in our model. Some preliminary simulation resultsindicate that this method used to define two parameters of 45mm motormodel is practicable. This work may establish basic foundation for nonlinear modeling of USM.

Contact Mechanics of Traveling Wave Ultrasonic Motors

In the pursuit of high areal recording density towards 10 Tb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , it is necessary to improve the positioning accuracy of the magnetic head in the hard disk drive head-positioning control system. Ultrasonic motors are novel electric motors well used in positioning control. Contact stresses can exist in the friction material and rotor. Obtaining the details of the stress distribution due to the inelastic deformation is important. A contact model of traveling wave ultrasonic motor (TWUSM) is proposed. A 2-D finite element model between stator and friction material is then developed. The evolution of deformation in friction material and rotor due to the mechanical surface loading is presented.