Multi-degree-of-freedom ultrasonic motors for mass-consumer devices

New approach to design active kinematic pairs, transforming resonant non-harmonic periodical vibrations into continuous motion is presented. The specifics of a piezoelectric motor utilizing this approach is that it can be made with limited size of arbitrary cross-section. Some examples of this type of piezomotor are presented, allowing creating miniature in-plane positioning systems and angular scanning systems. Examples of multi-degree-of-freedom piezomotors in mass-consumer devices are shown by “smart” toy prototypes made from standard LEGO™ construction blocks and mini figures.     

Ultrasonic motors: Their models, drives, controls and applications

In the last decades piezoelectrically driven ultrasonic motors have become alternative actuators to the conventional electromagnetic motors especially for precise and accurate servo positioning applications. Different types of ultrasonic motors have been constructed and manufactured. Several drive systems have been designed, implemented and proposed for these motors. A variety of control techniques have been applied to them. The research given in this study covers bases of the ultrasonic motors. Theoretical background, modeling, drive systems, control techniques and applications of the ultrasonic motors have been introduced. Firstly, the general overview has been given. Then, modeling studies focused on performance estimation and analysis of ultrasonic motors have been examined. Afterwards, drive systems and control techniques of ultrasonic motors have been investigated. Furthermore, an example drive and control system has been presented. This drive system has been designed as to be controlled digitally. In addition, the important industrial and research applications of these motors have been included. The presented study has been arranged as a review of ultrasonic motors. The important points of specifications, models, drive systems and control methods of the ultrasonic motors have been emphasized.     

Control characteristics for quasi-optimal operation of switched reluctance motors

This paper presents the control characteristics of switched reluctance (SR) motors defined for the maximum efficiency of the motor or the motor–converter system and for the minimum ripple level of electromagnetic torque. Curves for control variables—switch-on and switch-off angles (or conduction angle) and average phase voltage—are obtained by computations from a simple mathematical model. This lumped-parameter model takes into account the magnetic saturation of the motor and the parameters of the power converter necessary to guarantee reliable results concerning power losses in the system. The investigations were carried out for two typical SRM with the number of teeth N_s/N_r=8/6 and 6/4 for a battery supply and for a 310-V rectifier supply. Time curves obtained from mathematical model and control characteristics resulting from numerous optimization computations were validated by thorough measurements performed on a special test rig.List of symbols D viscous friction damping, Nms - e_k back EMF in the kth winding, V - i_k current in the kth winding, A - J moment of inertia, kg/m² - L() phase winding's inductance in unsaturated state H - L(,i) phase winding's inductance considering saturation H - m number of phases - N_s/N_r number of teeth: stator/rotor - n rotational speed, 1/s - R phase winding's resistance, - R_i current measurement resistor value, - R_k total resistance in the kth phase circuit, - R_s resistance of a power source, - R_TDSat drain-source resistance of a transistor in the saturated state - r_D dynamic resistance of a diode, - T_e electromagnetic torque, Nm - T_l load torque, Nm - u_k voltage of the kth phase, V - U phase voltage RMS value, V - U_av phase voltage average value, V - _on switch-on angle, rad - _off switch-off angle, rad - _z=_on–_off conduction angle, rad - stroke angle of the motor, rad - _s efficiency of a motor - _u efficiency of a motor–converter system - rotor position angle, rad - (,i) saturation function of the winding's inductance - m_p level of the torque ripples, % - _r=2/N_r, rad rotor tooth pitch - _k rotor position angle reduced to the kth tooth-pitch, rad - (,i) flux linkage of a phase winding, Wb - angular velocity, rad/s - angular acceleration, rad/s²     

超声波电机驱动控制系统建模与仿真

总结了超声波电机驱动控制系统建模与仿真研究的现状,指出必要的数学模型和建立在模型基础上的仿真分析是研究超声波电机驱动控制系统的一种重要手段,并对未来发展进行了展望。     

On the design of high‐efficiency linear induction motors for linear metro

Linear metro with single‐sided linear induction motor (SLIM) propulsion and wheel‐on‐rail support and guidance came into service in April 1990 in Osaka and in December 1991 in Tokyo, and is under construction or planned for Yokohama, Kobe, and Fukuoka. Since the new traffic system is used widely, it is of great importance to decrease its energy consumption. In this paper, the design of the SLIM for the linear metro is formulated as a constrained nonlinear programming problem, and optimum design is carried out to maximize efficiency. Seven parameters are chosen as independent variables: number of poles, pole pitch, stack height, secondary aluminum sheet thickness, overhang length, slot width/slot pitch ratio, and rated slip. The output KW/input KVA ratio, maximum flux density in teeth, temperature rise, primary length, stack height, overhang length, maximum thrust, and vertical force are selected as constraint functions. In the optimization procedure, the performance characteristics are formulated by space harmonic analysis taking account of the end effect, skin effect, and air gap leakage. The accuracy of the formulas is verified against experimental results. Effective ways of increasing efficiency include the addition of a copper reaction plate and minimization of the mechanical clearance. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 36–43, 2001     

Modeling of a cylindrical ultrasonic motor based on the single crystals

A novel cylindrical ultrasonic motor based on Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ crystals is proposed. Timoshenko beam theory and Lagrange equation are used to analyze the dynamics behavior of the stator. The contact behavior between the hemispherical rotor and the cylindrical stator is simulated by Hertz theory. The general modeling is established to estimate the ultimate performance of the prototype motor. The numerical results and the mechanical measurements from the prototype motor validate the theoretical analysis.     

大功率直线感应电动机推力脉动研究

直线电机边端效应是由定子铁心、次级开断所致的固有效应,该效应会引起电机电磁推力的不同频率的脉动。本文首先基于电磁推力公式对边端效应所致的推力脉动频率进行了理论分析。然后利用一维磁路法对动态纵向边端效应引起的次级感应涡流沿轴向的分布规律进行了理论分析和解析计算,根据次级感应涡流进而计算得到了动态纵向边端效应引起的转差频率两倍频推力脉动幅值的解析表达式,并得到了推力脉动幅值和不考虑边端效应时的电磁推力值的比例关系,最后通过峰值功率20 MW,最大出力900 k N的大功率直线感应电动机实验系统对分析结论进行了试验验证。理论分析和试验结果表明:计及边端效应时直线电机电磁推力存在供电频率两倍频和转差频率两倍频的脉动,其中转差频率两倍频的脉动由动态纵向边端效应导致,主要和次级极数以及转差频率有关。     

Relation between thrust constant and size in design of moving-coil linear dc motors

In this paper, the relationship between the limit value of the thrust constant and size of a linear dc motor (LDM) of moving coil type with unipolar design is described. The relationship between the limit value of the thrust constant of the LDM and the dimension of the yokes is deduced. Its relation is defined as the relational equation. To maximize the ratio of thrust to the volume of LDM, the magnetic flux density in the yoke is adjusted to the value of magnetic saturation. As a result, the following can be observed: the thrust constant is in inverse proportion to the stroke and is proportional to the sectional area of the center yoke. By measuring the thrust of the LDM and using the results of magnetic field analysis (finite element method), the validity of this observation is confirmed. The relation qualitatively agrees with the measurements, and its maximum error is 26.0 percent. Two LDMs are designed to verify the accuracy of our relational equation. One LDM is thin (maximum thickness is 14 millimeters) with long stroke (100 millimeters) for a pen recorder. The other LDM is for a high-speed positioning system with strong thrust (20 newtons). The relational equation agrees well with the measured thrust constant, with an error of about 14 percent. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 45–54, 1998     

Linear stepping ultrasonic motor

A linear stepping ultrasonic motor, based on vibrators alternative driving and slider grooves positioning, is proposed in this paper. The step-by-step movements can be obtained by exciting two vibrators of stator by turns. The motor is capable of bi-direction stepping movements without accumulative position errors driven by an open-loop control circuit, which provides single-phase sinusoidal signal via a switch unit to the vibrators. Its step displacement is 1 mm. The speed without load in one step is 7.69 ∼ 8.33 mm/s, and the blocking force is 0.12 ∼ 0.35 N in operating frequency 30 kHz and operation voltage 300 Vpp.     

动磁式永磁直线无刷直流电机气隙磁场的解析分析

为了解动磁式永磁直线无刷直流电机内气隙磁场的分布,用解析法对电机的气隙磁场进行了数学建模.通过求解拉普拉斯方程,计算了电机内气隙磁场的二维标量磁势,进而得到了电机内气隙磁感应强度的解析式.用建立的解析模型和有限元法分别对定子表面的气隙磁感应强度进行计算,发现两者的计算结果能够很好的吻合,验证了解析模型的正确性.用解析法讨论了占空比、磁极厚度和气隙长度变化对气隙磁感应强度产生的影响,结果表明气隙磁感应强度随永磁体厚度的增加而增大,但会逐渐进入饱和;而气隙磁感应强度也会随着气隙长度的变大而减小.通过对气隙磁场的分析,为相应电机的设计提供了依据.     

五相步进超声波电机驱动电源的研究

介绍了五相步进超声波电机的结构、运行机理，在对其定子的主振型和幅值分布仿真的基础上，提出了五相步进超声波电机的驱动控制要求，并给出了设计方案，对其中的主模块，如PWM模块等进行了仿真分析，利用频域法对输出波形进行了分析。结果表明：该驱动电源可以实现五相步进超声波电机的80步步进运动和正反转控制等。该电路具有调试简便等特点，可应用于步进超声波电机的驱动控制实验中。     

Characteristic matching between stator and rotor in standing-wave-type ultrasonic motors

This work discusses kinematical and dynamic matching between stator and rotor in standing-wave-type ultrasonic motors. A remarkable feature of standing-wave-type ultrasonic motors is that the stator intermittently contacts the rotor. The dynamic responses of the rotor in rotary direction and in pre-pressure direction influence the performances of the motor. The responses in the two directions have been investigated independently, because the two degrees of freedom are orthogonal in physics. To enhance drive force, rotation velocity and to reduce noise, the contact not only must be short enough but also must occur in the largest velocity area of the stator in the rotary direction of the rotor. The discussions presented in this paper can be used for guiding in the design of standing-wave-type ultrasonic motors.     

“工字形”直线超声电机的结构设计与模态分析

为了提高直线超声电机的输出性能,研制了纵弯复合模态“工字形”直线超声电机,对“工字形”弹性体的几种复合振动模态及其驱动方案进行了分析,确定了振子的工作模态。完成了“工字形”振子的结构设计,利用ANSYS软件对“工字形”压电振子进行了优化设计,确定了定子各结构参数。纵向伸缩振动模态固有频率和弯曲振动模态固有频率分别为33.07kHz和33.08kHz,频率差8Hz。根据优化设计结果,试制了原理样机。对样机的输出性能进行了实验研究。实验结果表明:当驱动频率为31.10 kHz,激励电压峰峰值为250V时,电机动子Vmax为240mm/s;驱动力Fmax为0.5N。     

Investigation of equations for calculation of secondary resistance and secondary leakage reactance of single-sided linear induction motors

In the linear induction motor, the original equations of the secondary equivalent circuit quantities derived from the two-dimensional electromagnetic analysis were expressed in combination with hyperbolic functions and trigonometric functions of complex numbers. In this paper, we attempt to deduce the equations for calculation of the secondary resistance and the secondary leakage reactance referred to the primary. These equations are approximated by a Maclaurin expansion and are expressed by polynomial approximation. This paper also shows the variation of those equivalent circuit parameters with slip and the change of the operating characteristics with the thickness of the secondary conducting plates. © 1998 Scripta Technica. Electr Eng Jpn, 122(1): 60–67, 1998     

Position sensorless control for ultrasonic motors based on input voltage information

This paper presents a method of position sensorless control of ultrasonic motors (USM). The position sensorless control method is useful for reducing the cost and size of drive system. The position estimation method is based on the input voltage information of the ultrasonic motor. The characteristic of input voltage versus rotor position is expressed by a quadratic function which is used to estimate a rotor position based on input voltage information. This estimation method, which uses only the drive voltage of the ultrasonic motor, is a very simple algorithm and shows good estimation ability. The parameters of the quadratic function are adjusted by using the recursive least squares method and are obtained on‐line. Since it can correspond to parameter change, the estimated rotor position shows good agreement with the measured rotor position against load torque and motor temperature changes. Sensorless position control is achieved by using the estimated rotor position instead of the measured rotor position. The validity of the proposed method is confirmed by experimental results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 57–64, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20626     

电动汽车驱动用永磁同步电动机控制系统的研究

电动汽车的研究开发已引起足够的重视。本文针对电动汽车的运行特点,给出了用于其驱动的PMSM的控制策略。并完成了以80C196KC单片机为核心的控制系统。实验表明:样机整体系统具有优良的性能,能够满足电动汽车驱动的要求。     

低速直线驱动系统研究现状分析

在介绍低速直线异步电机和低速直线永磁电机发展的基础上,给出了低速直线永磁同步电机基本结构、工作原理及主要特点,最后从低速直线电机结构设计、研究内容、研究方法等方面指出研究中存在的问题及今后研究的重点.     

Study of drive system for linear induction motor using magnetic energy recovery switch

This paper proposes a power supply suitable for driving linear induction motors. The power supply consists of a voltage source inverter (VSI) and a magnetic energy recovery switch (MERS). Circuit configuration and operation principles of the power supply are described. Power factor correction by MERS can increase the output power. Technical advantages of using MERS compared with increasing the rated voltage of VSI are discussed. Some experiments with a linear induction motor were conducted. The results confirm that MERS can reduce the capacity of the VSI or increase the output with the same VSI capacity. The number of devices and magnitude of losses are evaluated on a large‐scale drive system. A half‐bridge type of MERS is provided and discussed. The half‐bridge MERS mitigates disadvantages of using MERS. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 65–74, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20832     

Use of compensating magnets to reduce thrust imbalance in cylindrical linear pulse motors

A linear pulse motor (LPM) has many advantages for a high-accuracy positioning actuator because it has linear motion without any mechanical link. The flat-type LPM generally is used in many industrial applications. However, it has a disadvantage in that the mover support mechanism becomes complex and heavy because the attraction force between the stator and the mover is very large. As the attraction force is balanced in the cylindrical structure, the cylindrical LPM is allowed to have a simple and lightweight support mechanism. The inset magnet-type cylindrical LPM, which has a permanent magnet between the A-phase and B-phase stator, has such merits as a magnet of simple shape and a reduction of the motor diameter. Its weak point is that thrust unbalance occurs because the magnetic flux pass of the outer poles is longer than that of the inner poles. The thrust unbalance decreases the pull-in thrust force and increases the positioning error. This paper proposes two practical methods to improve the thrust unbalance: 1) the exciting current adjustment; and 2) the method with compensation permanent magnet. These effects are examined with theoretical and experimental results.     

Analysis of moving magnet linear dc motor with two straight stators

The thrust force of moving magnet-type linear direct current motors (MM-LDM) is analyzed in this study. A moving magnet-type MM-LDM consists of a stator and a carriage. The stator is composed of two stick shaped electromagnetics and the carriage consists of a movable permanent magnet that is located between the two electromagnets. One of the methods for calculating the thrust force of an MM-LDM is to analyze the energy gradient which is determined by the distribution of magnetic flux. However, this method is very difficult when used to calculate the thrust force of this kind of LDM. This type of MM-LDM can be considered to be a transformer in which the magnet of the mover is assumed to be a one-turn coil carrying a large current. The stored energy in the MM-LDM can be obtained by measuring the self-inductance and the mutual-inductance of the equivalent circuit of the MM-LDM. And this energy gradient gives the thrust force. The calculation of the thrust force induced in this motor shows that the mutual inductance has a large influence on the generation of thrust force.