Piezoelectric stepper motor with direct coupling mechanism to achieve high efficiency and precise control of motion

The paper describes a piezoelectric motor that combines the merits of piezoelectric materials, such as high power density generated at electromechanical resonance, and a precise control of displacement. In the motor, a standing shear wave is excited at the resonance in the piezoelectric tube, and it produces high-frequency torsional vibrations of the stator. The vibrations are converted into unidirectional rotation of a rotor by using a direct coupling mechanism between the stator and the rotor in which a clutch drives the rotor via locking it. The direct coupling makes it possible to transmit the whole power generated in the piezoelectric tube to the rotor, and thus achieve the high efficiency of the motor. It also allows combining two regimes of operation: continuous rotation and a stepwise motion within a 360 degrees interval with a high resolution of angular displacement.     

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N.m was achieved in the prototype, an improvement over previous versions.     

正交压电复合材料层板各类边界的解析解

压电复合材料层板由压电片与纤维层叠合而成。基于等效单层理论的位移场和电势场,针对正交铺层压电复合材料层板柱面弯曲问题,建立了力电耦合平衡方程,获得了一般边界的解析解。解析解由特解和通解两部分组成,特解对应于简支边界条件,通解由其他各类边界条件确定。平衡方程的变量仅4个,且不随层数变化。如采用相应的位移和电势分布函数,可以得到一阶理论、高阶理论、指数型理论等多种理论的解析解。算例中给出了各种边界条件下位移、应力和电势的解,讨论了各种理论的精度,观察到了固支边界的应力奇异现象。     

An ultrasonic piezoelectric motor utilizing axial-torsional coupling in a pretwisted non-circular cross-sectioned prismatic beam

A rotary piezoelectric motor design with simple structural components and the potential for miniaturization using a pretwisted beam stator is demonstrated in this paper. The beam acts as a vibration converter to transform axial vibration input from a piezoelectric element into combined axial-torsional vibration. The axial vibration of the stator modulates the torsional friction forces transmitted to the rotor. Prototype stators measuring 6.5 x 6.5 x 67.5 mm were constructed using aluminum (2024-T6) twisted beams with rectangular cross-section and multilayer piezoelectric actuators. The stall torque and noload speed attained for a rectangular beam with an aspect ratio of 1.44 and pretwist helix angle of 17.7 degrees C were 0.17 mNm and 840 rpm with inputs of 184.4 kHz and 149 mW, respectively. Operation in both clockwise and counterclockwise directions was obtained by choosing either 70.37 or 184.4 kHz for the operating frequency. The effects of rotor preload and power input on motor performance were investigated experimentally. The results suggest that motor efficiency is higher at low power input, and that efficiency increases with preload to a maximum beyond which it begins to drop.     

Numerical analysis of the symmetric hybrid transducer ultrasonicmotor

In this paper, operation of a symmetric hybrid transducer ultrasonic motor with output produced by two rotors connected together via a drive shaft is numerically analyzed and compared with the traditional asymmetric hybrid transducer motor design that produces its output from only one rotor. A one-dimensional finite element model for torsional vibration in the stator and a Coulomb friction model for rotor/stator contact associated with the longitudinal vibration of the motor are introduced. The calculation results demonstrate that the symmetric design is capable of performance comparable with the traditional asymmetric design when an optimum static spring force in the rotor/stator contact interface is applied during operation     

层合板中压电作动器最优厚度和嵌入位置研究

研究了压电结构中压电片厚度和嵌入深度的优化问题。首先给出了压电层合板的高阶耦合分析模型;然后以不受约束的含压电铺层复合材料板为代表,在压电层厚度方向施加电场时板自由变形,假设板任意微元横截面上内力为零,以其弯(扭)曲曲率最大为优化目标,建立了求解压电片最优厚度和嵌入深度问题的约束优化模型。最后分别以各向同性板中嵌入各项同性压电片和复合材料板中嵌入各向异性压电片为例进行了分析,绘出了目标函数的三维曲面图及等高线图,结果表明压电片的作动效能与其厚度和嵌入位置密切相关,而最优厚度和嵌入位置是由压电片和基体的材料特性决定的。     

L-shaped piezoelectric motor--part II: analytical modeling

This paper develops an analytical model for an L-shaped piezoelectric motor. The motor structure has been described in detail in Part I of this study. The coupling of the bending vibration mode of the bimorphs results in an elliptical motion at the tip. The emphasis of this paper is on the development of a precise analytical model which can predict the dynamic behavior of the motor based on its geometry. The motor was first modeled mechanically to identify the natural frequencies and mode shapes of the structure. Next, an electromechanical model of the motor was developed to take into account the piezoelectric effect, and dynamics of L-shaped piezoelectric motor were obtained as a function of voltage and frequency. Finally, the analytical model was validated by comparing it to experiment results and the finite element method (FEM).     

单振子二自由度球面马达的运动机理

利用矩形板形压电振子的两种振动模态,构建了一种采用单片压电振子驱动球形转子,形成两个旋转自由度的压电球面超声马达,对马达的作用机理进行了仿真分析和试验验证.利用有限元法对马达的矩形板压电振子的振动模态、共振频率进行了分析计算,仿真结果表明矩形板压电振子能够形成振型清晰的B32和B23振动模态,模态频率分别为49.127 kHz和49.756 kHz.对压电振子上每个凸起与球形转子之间的接触点的运动轨迹进行了计算机仿真,并对仿真结果进行了试验验证.分析结果表明各接触点能有效形成时序合理的椭圆运动轨迹,作为支撑足的一组凸起的变形量占作为驱动足的一组凸起的变形量的30%,能够用于驱动球形转子形成二自由度转动.仿真分析和试验结果证明了二自由度球面马达球形转子形成二维运动的作用机理.     

压电纤维复合材料桨叶的动力学建模

建立了压电纤维复合材料桨叶的非线性动力学模型。在此基础上,研究了压电纤维铺层对复合材料桨叶固有频率和桨叶扭转运动阻尼特性的影响。计算结果表明：桨叶扭转角变化量随着压电纤维施加电压的增加而增大;当电压为1000 V时,桨尖扭转角变化量大约为2°。压电纤维铺层对桨叶固有频率几乎没有影响,其存在不会改变原设计复合材料桨叶的频率分布。当压电纤维铺设方向与桨叶展向成45°时,其对桨叶扭转方向的阻尼特性有着很大的影响;采用适当的电压控制,可以明显增加扭转方向的阻尼。     

Rotor Design and Finite Element Analysis of Traveling Wave Rotaty Ultrasonic Motor

The dynamic transfer mechanism of the traveling wave rotary ultrasonic motor rotor-stator' s contact surface is studied in the paper and the key parts stator and cone flexible rotor of ultrasonic motor are designed.The three-dimensional contact model and finite element model considering the radial sliding between the rotor and the stator are established. The relation between the stator surface particle that amplitude frequency characteristics,resonance speed,radial displacement of ultrasonic motor and the tooth height are analyzed. Mass point radial relative displacement of contact surface between the cone flexible rotor,flexible rotor and the stator are contrasted. The cone flexible rotor is better placed on the surface of the stator tooth through its elastic deformation is interpreted. The cone flexible rotor reduces the radial slip between the stator and the output efficiency of ultrasonic motor is improved. The displacement trajectory of the stator surface is synthesized in a row wave cycle. The method of the stator mass point elliptical motion drives the rotor rotation is verified.     

Exact Solutions for the Analysis of Piezoelectric Fiber Reinforced Composites as Distributed Actuators for Smart Composite Plates

Performance of a layer of piezoelectric fiber reinforced composite (PFRC) material as the distributed actuator for smart composite plates has been investigated in this paper. The investigation is performed by finding the exact solutions for static analysis of simply supported symmetric and anti-symmetric cross-ply laminated plates integrated with a layer of PFRC material. The results suggest the potential use of PFRC materials for the distributed actuators of smart structures with both thick and thin substrate composite plates.     

Exact Solutions for the Analysis of Piezoelectric Fiber Reinforced Composites as distributed Actuators for Smart Composite Plates

Performance of a layer of piezoelectric fiber reinforced composite (PFRC) material as the distributed actuator for smart composite plates has been investigated in this paper. The investigation is performed by finding the exact solutions for static analysis of simply supported symmetric and anti-symmetric cross-ply laminated plates integrated with a layer of PFRC material. The results suggest the potential use of PFRC materials for the distributed actuators of smart structures with both thick and thin substrate composite plates.     

Force transfer model and characteristics of hybrid transducer type ultrasonic motors

The characteristics of longitudinal-torsional hybrid transducer-type ultrasonic motors (HTUSM) are low speed and high torque. The discontinuous-surface-contact mode between the stator and the rotor is different from the many-point-contact mode of traveling wave motors, which is also an essential cause for high torque. Therefore, it is important to analyze its force transfer model between the rotor and the stator. In this paper, issues of using the method of equivalent circuit model are addressed. The relationships between the contact angle, preload, and physical parameters of frictional materials are given, according to the impulse conservation law axially. The equations describing output torque, amplitudes of longitudinal and torsional vibration, and parameters of the rotor are derived according to the principle that the work done by the load is equal to that by the driving force in one vibrating cycle. All factors that influence the mechanical characteristics are analyzed, and accuracy and suitability of the force transfer model are verified by comparison with the prototype motor. The formula for transfer efficiency on the stator/rotor interface is given, and the low-efficiency of this type motor is explained. The wide-working frequency range property of this type motor is shown with experimental results. Based on this study, the parameters of the rotor and preload are determined. The maximum torque of the prototype motor is up to 13.2 nm, and no-load speed of this type of motor is 12.5 rpm.     

A smooth impact rotation motor using a multi-layered torsional piezoelectric actuator

A smooth impact rotation motor was fabricated and successfully operated using a torsional piezo actuator. Yoshida et al. reported a linear type smooth impact motor in 1997. This linear motor demonstrated a high output force and a long stroke. A superior feature of the smooth impact drive is a high positioning resolution compared with an impact drive. The positioning resolution of SIDM (smooth impact drive mechanism) is equal to the piezo displacement. The reported positioning resolution of the linear type was 5 nm. Our rotation motor utilized a torsional actuator containing multi-layered piezoelectric material. The torsional actuator was cylindrical in shape with an outer diameter of 15 mm, an inner diameter of 10 mm, and a length of 11 mm. Torsional vibration performance was measured with a laser Doppler vibrometer. The obtained torsional displacement agreed with the calculated values and was sufficient to drive a rotor. The rotor was operated with a saw-shaped input voltage (180 V; 8 kHz). The revolution direction was reversible. The maximum revolution speed was 27 rpm, and the maximum output torque was 56 gfcm. In general, smooth-impact drives do not show high efficiency; however, the level of efficiency of our results (max., 0.045%) could be increased by improving the contact surface material. In addition, we are studying quantitative consideration, for example, about the optimum pre-load or frictional force.     

HSDT-layerwise analytical solution for rectangular piezoelectric laminated plates

The present paper develops a formulation for laminated plates with extensional distributed piezoelectric sensors/actuators. This formulation is based on linear electroelasticity, and an equivalent single layer is used for the mechanical displacement field, applying a Higher-Order Shear Deformation Theory (HSDT), whereas a layerwise discretization is used in the thickness direction for the electric potential. The electric and mechanical local equilibrium equations and local constitutive equations for the problem are identified. The Principle of Virtual Work is used to derive the dynamic equilibrium equations in terms of generalized forces and the consistent boundary conditions. The piezoelectric laminate constitutive equations are built and used to write the equations of motion in terms of generalized displacements. Finally, analytical solutions for simply supported square laminates with piezoelectric layers are developed. The entire laminate, composed of the base structure and piezoelectric layers, can be arbitrary orthotropic. The solution is adequate for an arbitrary number of piezoelectric layers and stacking positions. Moreover, the solution takes into account all material coefficients, whether mechanical, piezoelectric or dielectric. Analytical results are obtained for static bending, both in sensor and actuation modes, and for free vibration of symmetric cross-ply laminates with piezoelectric layers externally bonded to the plate.     

复合式罩极电机扭转振动检测与分析

设计了一种复合式罩极电机,为双定子双转子结构,电机运行时定子绕组施加励磁,产生的旋转磁场带动转子旋转。分析了电机气隙磁场的特性,推导了电磁转矩公式,表明电机运行时存在扭转振动。研制了复合式罩极电机样机,利用传感器对电机在不同励磁状态下的转矩输出进行了检测,表明电机运行时存在扭转振动,且扭振幅值随两相励磁电压的相位差而变化,最后对变化规律进行了理论分析,结果表明:扭转振动波的相位差为两相励磁电压相位差的2倍。     

A piezoelectric motor using flexural vibration of a thin piezoelectric membrane

This paper describes a new implementation of a disk-type piezoelectric motor, whose stator is a commercial available piezomembrane composed of a nickel alloy disk to which a piezoceramic disk is bonded. The two disks are concentric, and the total thickness is very small. Ultrasonic motors are based on the concept of driving a rotor by mechanical vibration excited on a stator, via the piezoelectric effect. The rotor is in contact with the stator, and the driving force is the frictional force between rotor and stator. To transform the mechanical vibration of the stator in the rotor rotation, a traveling wave must be excited on the stator surface. The proposed motor can be regarded as a disk-type, single wavelength motor in which the traveling wave is due to the natural flexural vibration of the piezomembrane at low frequency. The behavior of the stator is analyzed both theoretically, by using the theory of isotropic and homogeneous vibrating plates, and by means of a commercial finite element computer code, finding a good agreement with the experimental results. The main features of the motor are very small thickness, appreciable torque, and high speed, obtained with low input power at low voltage; the intended application is to substitute the moving-coil in analogic instrumentation.     

压电类智能层合结构的力学和计算模型综述

综述了压电类智能层合结构的力学和计算模型。基于大量国内外有关压电类智能层合结构的文献 ,根据各自采用的运动学假设、场变量的近似、压电层的表达法以及曲率和温度的影响 ,对压电层合结构的力学和计算模型进行了分类 ,阐述了各种理论的特点及一般形式。     

Effect of stacking sequence on the torsional stiffness of the composite drive shaft

Torsional stiffness is an important parameter judging the performance of composite drive shaft. In this paper, a new mechanical analytical solution of torsional stiffness for the composite drive shaft with balance laminate is derived based on classical lamination theory and mechanical analysis. Finite element analysis (FEA) has been used to calculate the torsional stiffness of carbon fiber-reinforced plastic (CFRP) drive shaft. A torsion test platform has also been constructed to measure the torsional stiffness of CFRP drive shaft specimens. Results of the mechanical analytical solution, FEA, and experiments show that the composite tube with the location of ±45° layers near to the outer surface is larger than the ones with the location of ±45° layers near to the inner surface. The effect of stacking sequence on torsional stiffness is larger in the thick-walled than that in the thin-walled composite drive shaft. The mechanical analytical solution can complement classical lamination theory which cannot reflect the effect of stacking sequence in calculating the torsional stiffness.     

Piezoelectric ultrasonic motor using longitudinal-torsional composite resonance vibration

A piezoelectric ultrasonic motor, which uses longitudinal and torsional composite vibration, is examined in order to obtain high torque characteristics with small diameter. Piezoelectric ceramic elements, oscillating in both longitudinal and torsional modes, respectively, are used as piezoelectric stiffened modes having high electromechanical coupling factors k(33) and k(15), respectively. It is found that the resonant frequencies for longitudinal mode and torsional mode could coincide with each other in the ultrasonic motor, according to finite element method analysis and experimental measurement. The motor operating in both resonant vibrations indicated good performance. The 20-mm diameter motor exhibited 4 kgfcm maximum torque, 450 r/min maximum rotational speed, 40% maximum efficiency, and quick responsiveness, within 2.5 ms.