弯振复合型超声驱动器振动特性研究

为了避免模态复合型超声驱动器中普遍存在的频率简并问题,作者在前期研究中提出了一种新型的弯振复合型超声驱动器。该驱动器采用压电金属复合梁两个正交弯振模态的复合在两个驱动足处激励出椭圆轨迹振动。本文对该驱动器的振动特性进行深入研究,旨在获得驱动区域质点的真实运动轨迹。首先,建立了矩形截面梁在弯振复合模态下末端区域质点振动轨迹的数学模型;然后,借助有限元瞬态分析,对驱动足振动轨迹进行仿真,实现对所建立振动轨迹数学模型的验证。振动轨迹方程和仿真结果均表明：两个驱动足表面质点振动轨迹均为三维的椭圆,垂直于驱动器轴线的平面内的椭圆振动更适合用于致动输出。最后,分析了该驱动器存在的不足之处,提出了一种改进方案,采用对称设置压电陶瓷片实现两个驱动足振动特性的一致;通过瞬态分析在两个驱动足处得到了一致的振动轨迹,改进的样机实现了输出特性的显著提高。     

十字形压电振子同型模态振动驱动的平面电机

提出十字形压电振子同型模态驱动的压电平面电机新原理,选定该振子的面外弯振、面内横杆弯振、面内纵杆弯振为工作模态,利用面外弯振分别与面内纵杆弯振、面内横杆弯振的振动耦合,在纵、横杆驱动足上生成沿x Oz、y Oz面行进的椭圆轨迹以推动动子沿x、y向移动。阐明电机驱动原理,优化出振子尺寸为60 mm×60 mm×7.8mm,厘定电机最适驱动频率为30 127 Hz。建立振子机电耦合模型,研究驱动足的振动特性,模拟出驱动足的椭圆轨迹,仿真得到在250 V电压激励时驱动足的x、y、z向振幅分别为1.6μm、1.6μm和1.2μm。建立电机的整机分析模型,探析驱动电压、频率、相位差、预紧力对电机速度的影响。在正常驱动条件下,电机速度可达50 mm/s。该电机在平面装置驱动中的应用前景广泛。     

纵振换能器式圆筒型超声电机振动特性的研究

以纵振夹心换能器式圆筒型超声电机为研究对象,对换能器的振动状态进行了分析,给出了换能器弯曲振动的产生原因;研究了耦生弯振对电机机电耦合系数以及圆筒中弯振行波质量所带来的影响,耦生弯振的存在使得定子模态特征频率偏离换能器谐振频率,并使得定子圆筒中的弯振行波产生了畸变。最后,提出一种采用换能器弯振激励圆筒径向弯振的模态组合方式。     

双十字压电振子同型弯振模态驱动的平面超声电机

为了丰富平面超声电机的型式,提出一种双十字压电振子同型弯振模态驱动的平面超声电机。利用双十字压电振子的纵杆面内、面外弯振耦合以及横杆面内、面外弯振耦合,分别在两杆的驱动足上合成沿xoz、yoz面行进的两相椭圆轨迹,以交替地推动动子沿x、y向移动。分析了该平面超声电机的驱动机理,并推导出两相椭圆轨迹方程。建立了双十字压电振子机电耦合模型,对其三相工作模态的振型进行仿真分析,并在结构优化的基础上实现了三相工作模态频率一致,使它们分别为43 468,43 552和43 569 Hz。仿真了双十字压电振子的频响特性并实现了干扰模态分离,当驱动电压为250 V时,驱动足x、y、z向振幅分别为1.3,0.8和0.9 μm,满足电机驱动要求。模拟得到定频激励下双十字压电振子驱动足的两相椭圆运动轨迹,验证了所设计平面超声电机驱动机理的有效性。该平面超声电机可输出较大速度与动力,具有广阔的应用前景。     

U型变截面薄板面内复合模态驱动的直线超声电机

提出一种U型变截面薄板结构驱动的压电直线超声电机,选定U板两纵杆的一阶反对称纵振和二阶对称弯振为工作模态。阐释了电机驱动机理,推导了定子驱动端椭圆运动轨迹;基于纵、弯工作模态频率一致性模型,优化了电机结构尺寸;通过谐响应分析及激光测振试验,证实了定子工作模态的存在及其纯正性;设计出电机装配结构,制作出其原型样机;构建电机驱动控制平台,驱动电机运转,验证电机原理的可行性。通过速度特性试验发现:当驱动频率为78.11 kHz且电压幅值为240 V时,电机最大运动速度可达125.6 mm/s。     

单相斜轨塔形直线超声电机设计与实验

对一种理论斜直线运动轨迹的单相驱动双向运动的直线超声电机进行了理论及实验研究.该电机由塔形定子和倾斜一定角度安装的导轨组成,定子的两个正交工作模态为y-z面内对称振动模态和x-z面内弯振模态,分别对应电机的正反运动方向,利用在工作模态下定子驱动足表面质点相对于导轨的理论斜直线运动来驱动导轨运动.分析了电机的工作原理,推导了电机运行的导轨倾角范围,研制了样机,并进行了模态实验和机械特性实验.实验表明:在导轨倾斜角为35°、激励电压500 Vp-p、预压力4.5 N下,当电机工作在y-z面内对称振动模态,电机正向运动,最大空载速度为79 mm/s,最大输出力为0.5 N;当电机工作在x-z面内弯振模态,电机反向运动,最大空载速度为756 mm/s,最大输出力0.8 N.     

二自由度行波型超声波电机定子的数学模型与实验研究

二自由度行波型超声波电机是一种新型多自由度超声波电机。本文从二自由度行波型超声波电机的驱动机理和基本结构出发,就电机的结构实现、驱动球转子的最佳定子结构进行了分析,利用所建立的有限元模型进行定子振动的模态分析和共振频率计算,提出了外缘大倾角内缘线接触的行波定子。然后建立定子的接触模型,对其机械性能进行分析。测试结果表明,修正的数学模型更加符合电机的实际运行特性。所研制样机的球转子直径为45mm,定子直径为30mm,实现的堵转力矩为120mNm,空转转速12r/min。本文工作为多自由度行波型超声波电机的优化设计、性能提高奠定了基础。     

Ⅳ型弯张换能器的数字建模

Ⅳ型弯换能器的振动机理比较复杂,它包涵着驱动振子的振动、壳体的振动、水介质振动及它们之间相互耦合而构成的复合振动。本文对其进行了较详细的理论分析,给出了换能器壳体的振动位移分布和谐振频率。并根据干模态讨论了换能器在水中的声辐射特性;再者,结合压电方程及换能器的振速、应力分布给出了换能器在水中的电机声等效电路。理论分析结果与有限元法及实验测量进行比较,符合较好。     

H-结构薄板纵弯复合模态驱动的压电直线电机

为高性能压电直线电机设计奠定基础,推出基于H型振子的直线电机并利用该振子两纵向杆面内一阶纵振与二阶弯振驱动电机。研究电机的驱动机理并从理论上阐释振子纵杆驱动端质点的椭圆运动形成过程;建立振子有限元模型并对其工作模态、灵敏度、谐响应进行分析;优化振子结构尺寸,完成电机装配结构设计并制作出振子、电机实物;对振子进行模态试验,结果显示该振子不仅具有预设的工作模态,且在正常激励条件下,驱动端纵、弯振幅值分别可达1.2 μm,1.4 μm。研究表明,该电机有望产生较大速度与动力。     

IV型弯张换能器的数学建模

ＩＶ型弯张换能器的振动机理比较复杂,它包涵着驱动振子的振动、壳体的振动、 水介质振动及它们之间相互耦合而构成的复合振动。本文对其进行了较详细的理论分析,给 出了换能器壳体的振动位移分布和谐振频率。并根据干模态讨论了换能器在水中的声辐射特 性;再者,结合压电方程及换能器的振速、应力分布给出了换能器在水中的电机声等效电路。 理论分析结果与有限元法及实验测量进行了比较,符合较好。     

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet

A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).     

A rotary ultrasonic motor using bending vibration transducers

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

Transducer for high speed and large thrust ultrasonic linear motor using two sandwich-type vibrators

A transducer for an ultrasonic motor using two sandwich-type vibrators has been proposed and designed. The vibrators cross at right angles with each other at the tip. The transducer has two vibration modes; one is a symmetrical mode and the other is anti-symmetric. The normal direction motion of the transducer tip is excited by the symmetrical mode. The lateral motion of the tip is excited by the anti-symmetrical mode. The transducer is designed so that these vibration modes are degenerated. To obtain high output force and high power, materials were carefully selected. Heat-treated high strength chromium manganese steel bolts were used for binding the PZT elements. A zirconia ceramics plate was bonded on the transducer tip as frictional material. The no-load maximum speed was 3.5 m/sec. The output force was 39 N at the driving voltage of 500 V(rms) and the preload of 150 N. At this condition the maximum efficiency was 28%, and the velocity was 0.55 m/sec. The maximum output force was 51 N, which was 17 times of the transducer weight. The maximum output power per unit weight was 76 W/kg.     

Characteristic analysis and design of a B14 rotary ultrasonic motor for a robot arm taking the contact mechanism into consideration

The ultrasonic motor (USM) has many merits for use in a robot arm application. Therefore, the disk-type traveling wave B₁₄ rotary ultrasonic motor (RUSM) is proposed in this paper for that application. Up to the present time, the analysis and design of the USM have been almost always performed using rough analytic methods or using commercial analysis tools. As a result, it was impossible to achieve an exact analysis and design of the USM. In order to address this problem, this paper proposes the analysis and design methodology of the B₁₄ RUSM using a numerical method (3-D FEM) combined with an analytic method taking the contact mechanism into consideration in a linear operation. This methodology is applicable to many other kinds of USMs that use similar mechanisms. In addition, the mechanical system and the driving circuit of the B₁₄ RUSM are designed and prototyped. Finally, the proposed analysis and design methodology is validated by comparing its outcomes with the experimental data. Also, the appropriateness of the suggested RUSM for the application of a robot arm was verified     

Characteristic analysis and design of a B14 rotary ultrasonic motor for a robot arm taking the contact mechanism into consideration.

The ultrasonic motor (USM) has many merits for use in a robot arm application. Therefore, the disk-type traveling wave B14 rotary ultrasonic motor (RUSM) is proposed in this paper for that application. Up to the present time, the analysis and design of the USM have been almost always performed using rough analytic methods or using commercial analysis tools. As a result, it was impossible to achieve an exact analysis and design of the USM. In order to address this problem, this paper proposes the analysis and design methodology of the B14 RUSM using a numerical method (3-D FEM) combined with an analytic method taking the contact mechanism into consideration in a linear operation. This methodology is applicable to many other kinds of USMs that use similar mechanisms. In addition, the mechanical system and the driving circuit of the B14 RUSM are designed and prototyped. Finally, the proposed analysis and design methodology is validated by comparing its outcomes with the experimental data. Also, the appropriateness of the suggested RUSM for the application of a robot arm was verified.     

Analysis of a disk-type piezoelectric ultrasonic motor using impedance matrices

The dynamic behavior and the performance characteristics of the disk-type traveling wave piezoelectric ultrasonic motors (USM) are analyzed using impedance matrices. The stator is divided into three coupled subsystems: an inner metal disk, a piezoelectric annular actuator with segmented electrodes, and an outer metal disk with teeth. The effects of both shear deformation and rotary inertia are taken into account in deriving an impedance matrix for the piezoelectric actuator. The impedance matrices for each subsystem then are combined into a global impedance matrix using continuity conditions at the interfaces. A comparison is made between the impedance matrix model and the three-dimensional finite element model of the piezoelectric stator, obtaining the resonance and antiresonance frequencies and the effective electromechanical coupling factors versus circumferential mode numbers. Using the calculated resonance frequency and the vibration modes for the stator and a brush model with the Coulomb friction for the stator and rotor contact, stall torque, and no-load speed versus excitation frequencies are calculated at different preloads. Performance characteristics such as speed-torque curve and the output efficiency of the USM also are estimated using the current impedance matrix and the contact model. The present impedance model can be shown to be very effective in the design of the USM.     

Y形旋转超声波马达的设计与动态特性分析

为了探索和丰富旋转超声波马达的结构,使其满足响应精准且速度快以及控制简便的要求,设计了Y形旋转超声波马达,并对其结构及动态特性进行了分析。Y形旋转超声波马达将3组压电陶瓷片的横向振动复合成驱动足端面对转子的微幅驱动,通过摩擦耦合在惯性作用下推动转子顺时针或逆时针旋转。运用Workbench软件中的Design Exporation组件对Y形旋转超声波马达定子组件的结构尺寸进行了优化设计,提升了定子组件的性能。构建优化后Y形旋转超声波马达定子组件的有限元仿真模型,并通过模态分析获得了定子组件工作所需的固有振型,通过谐响应分析获得了定子组件的幅频特性曲线,通过瞬态分析获得了1个激励周期内定子组件的振动模态,验证了Y形旋转超声波马达的驱动机理。结果表明,Y形旋转超声波马达压电陶瓷片表面施加电压的最佳频率为20 739 Hz,对应的驱动足端面的振幅为6.95 μm。Y形旋转超声波马达结构简单且具有对称性,能效利用率高,对拓宽超声波马达的应用领域有重要参考价值。     

Rotary ultrasonic machining— a new cutting process and its performance

In conventional ultrasonic machining (USM), brittle materials are machined by using ultrasonic impacts on the workpiece, through a medium of abrasive slurry. In this paper a new cutting process that resulted due to introduction of an additional parameter, namely the rotation of the workpiece during the machining, is presented. This may be called ‘rotary ultrasonic machining’. The material removal rates (MRR) in rotary USM are up to four times those in conventional USM. The MRR increases with increase in speed of rotation of workpiece. An explanation for the superior performance of rotary USM is presented. The performance of rotary USM as a function of static load, abrasive grain size, concentration of abrasive slurry, diameter of tool and ratio of diameters of hollow tools, is studied and the parameters are optimized for minimum machining time or maximum material removal rate. Comparisons are made with conventional USM.