Theoretical analysis and experiments of axial flux pm motors with minimized cogging torque

This paper deals with analysis and experiments of an axial flux PM (AFPM) brushless dc motor with minimized cogging torque. Recently, many optimal designs for the AFPM motor have been done by finite element (FE) analysis, but such analysis is time-consuming. In this study, the equation of magnetic flux lines existing between PMs and core is assumed mathematically and the minimum cogging torque is calculated theoretically and geometrically without FE analysis. The form of equation is assumed to be a 2^nd order polynomial. The skew angle that makes the cogging torque minimized is calculated theoretically, and the value of minimum cogging torque is compared with the results obtained by FE analysis and experiments. The maximum cogging torque of a proposed AFPM motor has the smallest value approximately at a skew angle of 4° in both the theoretical and FE analysis. Compared with the non-skewed motor, the cogging torque of the skewed motor can be decreased to over 90%, which has a value of 5% of the rated torque. Two types of stator cores, with the skew angle of 0° and 4°, are analyzed, manufactured, and tested experimentally. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Dong Ho Kim received B.S. and M.S. degrees in Mechanical Engineering from Pusan National University in 1982 and 1984, respectively. He then received his Ph.D. degree from Yonsei University in 2007. Dr. Kim is currently a Professor at the Department of Automation and Robots at Kyonggi Institute of Technology in Gyeonggi, Korea. His research interests are in the area of production automation. Jong Hyun Choi received B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Yonsei University, Seoul, Korea, in 1996, 1998, and 2006, respectively. Dr. Choi is currently a post-doctor at the School of Mechanical Engineering at Yonsei University. His research interests are in the area of electromagnetic actuators and magnetic levitation system. Chang Woo Son received a B.S. from Kyungwon University, Seoul, Korea, in 2006, and his M.S. degree from Yonsei University in 2008, all in mechanical engi-neering. He is currently a research engineer at DA Laboratory of LG Electronics in Seoul, Korea. His research interests are in the area of electromagnetic actuators. Yoon Su Baek received B.S. and M.S. degrees from Yonsei University, Seoul, Korea, in 1979 and 1981, respectively, and M.S. and Ph.D. degrees from Oregon State University in 1986 and 1990, respectively, all in mechanical engineering. He worked for Samsung Heavy Industry Ltd. as head research engineer at Mechatronics Research Center from 1990 to 1993. Dr. Baek is currently a Professor at the School of Mechanical Engineering at Yonsei University. His research interests are motion devices and robotics, especially relating to multi-D.O.F. actuators. He is also interested in magnetic brake and levitation system.     

Simulation analysis of cogging torque of permanent magnet synchronous motor for electric vehicle

This paper proposes a new approach to study generation mechanism and influence factors of cogging torque of permanent magnet synchronous motors, in order to improve the operational performance and riding comfort of electric vehicle. Based on energy method and Fourier expansion, the method of predicting cogging torque is proposed. Two-dimensional finite element model of in-wheel motor is established by Maxwell software, and electromagnetic character of that is analyzed. Skew slot, pole arc coefficient and width of slot mouth are analyzed and studied by finite element method, in order to realize the change regularity of cogging torque. Cogging torque curves under the different skew slots, the different pole arc coefficients and the different widths of slot mouth are obtained, which can effectively reduce the cogging torque of in-wheel motor, but they still exists some limitations. The final simulation analysis results are in good agreement with the theoretical predicting results, which indicates that this method can be used to afford a theoretical basis to reduce the cogging torque and optimize the in-wheel motor of electric vehicle in the future.     

Output characteristics and experiments of a novel low frequency rotary piezoelectric motor

In order to improve the output performance of a piezoelectric motor under low driving frequency, a novel rotary piezoelectric motor driven by two piezoelectric actuators is proposed that is actuated based on harmonic and friction driving mechanism. The motor uses two piezoelectric actuators to drive two amplifying mechanisms with π/2 phase difference to produce harmonic motion, and then drives the rotor to rotate through friction force. Based on the driving principle, the electromechanical coupling equations of the motor are established. And a test platform is built to test the output characteristics of the motor. The results show that fluctuation of harmonic force and output torque occurs when the motor operates at different positions. Under the driving voltage and frequency of 150 V and 5 Hz, the actual average output torque of the prototype is 3.08 Nmm. Moreover, fluctuation of harmonic force and output torque occurs when the motor operates at different positions.

     

Fuzzy sliding mode controlled slider–crank mechanism using a PM synchronous servo motor drive

The dynamic response of a sliding mode controlled slider–crank mechanism, which is driven by a permanent magnet (PM) synchronous servo motor, is studied in this paper. The rod and crank are assumed to be rigid. The Hamilton’s principle and Lagrange multiplier method are applied to formulate the equation of motion. Reducing the differential-algebraic equations and employing the Runge–Kutta numerical method, the state variable representation is obtained. Moreover, based on the principles of the sliding mode control, a position controller is developed. Then, a simple fuzzy inference mechanism is utilized to estimate the upper bound of uncertainties for the sliding mode controller. Numerical results show that the dynamic behavior of the proposed controller–motor–mechanism system is robust to parametric variation and external disturbance.     

Modeling of a linear motor feed drive including pre-rolling friction and aperiodic cogging and ripple

This work addresses the systematic modeling of a linear feed drive based on a linear synchronous motor, a helpful step in control design for precise machine tools using linear motors. The model considers the electrical dynamics, ripple, cogging effects, and friction. For ripple and cogging, periodic and aperiodic behaviors are analyzed, and simple models are proposed to reflect the observed behavior. Friction is represented by the generalized Maxwell-slip model Al-Bender (IEEE Trans Autom Control 50:1883–1887, 2005), and the particular manner in which pre-rolling parameters and Stribeck curve were determined for the current system is shown here for completeness. Finally, the model shows a good performance both in simulation and feedforward control.     

Driving and braking control of PM synchronous motor based on low-resolution hall sensor for battery electric vehicle

Resolvers are normally employed for rotor positioning in motors for electric vehicles,but resolvers are expensive and vulnerable to vibrations.Hall sensors have the advantages of low cost and high reliability,but the positioning accuracy is low.Motors with Hall sensors are typically controlled by six-step commutation algorithm,which brings high torque ripple.This paper studies the high-performance driving and braking control of the in-wheel permanent magnetic synchronous motor(PMSM) based on low-resolution Hall sensors.Field oriented control(FOC) based on Hall-effect sensors is developed to reduce the torque ripple.The positioning accuracy of the Hall sensors is improved by interpolation between two consecutive Hall signals using the estimated motor speed.The position error from the misalignment of the Hall sensors is compensated by the precise calibration of Hall transition timing.The braking control algorithms based on six-step commutation and FOC are studied.Two variants of the six-step commutation braking control,namely,half-bridge commutation and full-bridge commutation,are discussed and compared,which shows that the full-bridge commutation could better explore the potential of the back electro-motive forces(EMF),thus can deliver higher efficiency and smaller current ripple.The FOC braking is analyzed with the phasor diagrams.At a given motor speed,the motor turns from the regenerative braking mode into the plug braking mode if the braking torque exceeds a certain limit,which is proportional to the motor speed.Tests in the dynamometer show that a smooth control could be realized by FOC driving control and the highest efficiency and the smallest current ripple could be achieved by FOC braking control,compared to six-step commutation braking control.Therefore,FOC braking is selected as the braking control algorithm for electric vehicles.The proposed research ensures a good motor control performance while maintaining low cost and high reliability.     

Design and characterization of a novel permanent magnet synchronous motor used in a growing prosthesis for young patients with bone cancer

Approximately 50 child sarcomas are treated with limb salvage surgery each year in the United Kingdom. These children need an extendable implant that can be lengthened periodically to keep pace with the growth in the opposite limb. Surgically, invasive devices have been used for the past 30 years with intrinsic problems of infection and long-term recurrent trauma to the patient. To eliminate problems associated with the invasive device, a noninvasive extendable prosthesis was developed. The magnetically coupled drive technology used for this prosthesis was a synchronous motor with a gear-driven telescoping shaft. In this design the motor configuration was in two parts: a rotating magnet (rotor) that fitted inside the prosthesis where space was limited and the stator, which was an external device used to extend the prosthesis remotely as the patient grew. This compact external drive produced a focused magnetic flux that required no cooling and operated on a single-phase power supply. The extending mechanism in the implant was able to overcome up to 1300 N force, which is the tension force exerted by the soft tissues during the lengthening procedure. The device has been successfully implanted in 50 patients.     

Control of a permanent magnet synchronous motor with a fuzzy sliding-mode controller

This paper is concerned with the topics in the speed control of a permanent magnet synchronous motor (PMSM). First, the vector control scheme in the synchronously rotating reference frame is used to formulate the PMSM model as the system plant. Then, the modern control theory using a sliding mode with fuzzy controller is presented to design the corresponding closed-loop system and Matlab/Simulink software is used for computer simulation. The original PMSM is stable, sluggish with large overshoot deficiency. It can be shown that the proposed fuzzy sliding-mode controller not only can delete the overshoot problem and achieve very good tracking performance without zero steady-state errors, but can also obtain good robustness to system parameter uncertainty. This proposed fuzzy-sliding mode controller for PMSM can be applied to the positioning control of the robot arms to suppress unnecessary vibrations. For assembly lines, this proposed controller can be used to obtain fast tracking ability, less steady-state errors, and robustness for different velocity movements.     

Analysis of the magnetic force and the torque in a brushless DC motor

As permanent-magnet motors and generators produce torque, vibration occurs through the small air gap due to the alternating magnetic forces created by the rotating permanent magnets and the current switching of the coils. The magnetic force can be calculated from the flux density by finite element methods and the Maxwell stress tensor in cylindrical coordinates. The transition of the magnetic force with the rotation of rotor and the commutation of current, was analyzed by assuming the quasi static magnetic field. The cogging and the commutating torques were also investigated by integrating the magnetic shear force in a small air-gap. In addition, the characteristics of these forces and torques were also investigated by multi-dimensional spectral analysis, so that this paper makes it possible to predict the frequency spectrum of magnetic force and the torque in a brushless do motor.     

永磁同步电机控制系统的建模与仿真分析

在建立了永磁同步电机数学模型的基础之上,仿真模型中包含了建立三相电流源型逆变器模块、DQ向ABC转换模块等,并改进了电流滞环控制模块。文中提出了一种分析永磁同步电机（PMSM）的新方法,分析了伺服系统在不同给定速度下的表现稳定性以及转矩电流的变化等。     

Precise speed control of a permanent magnet synchronous motor

Precise control of vibration modes become critical when one wants to push the state of the art with a permanent magnet synchronous motor (PMSM). In this paper, a complete control strategy, concerned about the design based model, controller design, and dealing with the shaping of the system input is presented. First, a modeling analysis is performed on the vector control scheme in the synchronously rotating reference frame that is used for controlling the PMSM. Then, the pole-placement scheme is used to design a desirable closed-loop system. After that, the shaped input technique together with the designed controller is considered to yield the shortest actual system input. The Matlab/Simulink software is used to perform the simulation. This simulation results verify that the eliminated oscillation response gives much better transient performance in the aspects of faster settling time and decreasing energy to supply for the PMSM.     

Precise speed control of a permanent magnet synchronous motor

Precise control of vibration modes become critical when one wants to push the state of the art with a permanent magnet synchronous motor (PMSM). In this paper, a complete control strategy, concerned about the design based model, controller design, and dealing with the shaping of the system input is presented. First, a modeling analysis is performed on the vector control scheme in the synchronously rotating reference frame that is used for controlling the PMSM. Then, the pole-placement scheme is used to design a desirable closed-loop system. After that, the shaped input technique together with the designed controller is considered to yield the shortest actual system input. The Matlab/Simulink software is used to perform the simulation. This simulation results verify that the eliminated oscillation response gives much better transient performance in the aspects of faster settling time and decreasing energy to supply for the PMSM.     

永磁直线同步电动机的磁场谐波扰动分析

分析永磁直线同步电动机的电磁推力,得出永磁体的磁链为影响推力的重要因素。通过温度和交变磁场频率对永磁体磁性影响的研究,以及由电动机定子电流、绕组间的自感和互感等,通过派克变换对端部效应的形成原因和谐波成分的分析,进一步明确了磁场谐波扰动对永磁直线同步电动机推力的影响。     

Analysis and experiments of a novel and compact 3-DOF precision positioning platform

A novel 3-DOF precision positioning platform with dimensions of 48 mm×50 mm×35 mm was designed by integrating piezo actuators and flexure hinges. The platform has a compact structure but it can do high precision positioning in three axes. The dynamic model of the platform in a single direction was established. Stiffness of the flexure hinges and modal characteristics of the flexure hinge mechanism were analyzed by the finite element method. Output displacements of the platform along three axes were forecasted via stiffness analysis. Output performance of the platform in x and y axes with open-loop control as well as the z-axis with closed-loop control was tested and discussed. The preliminary application of the platform in the field of nanoindentation indicates that the designed platform works well during nanoindentation tests, and the closed-loop control ensures the linear displacement output. With suitable control, the platform has the potential to realize different positioning functions under various working conditions.     

新型圆筒直线电机推力的解析与数值方法研究

提出了一种新型圆筒直线电机结构.建立了适合其结构特征的轴对称涡流解析方程,给出了方程的解析解.并采用变分方法建立了该轴对称场的有限元模型.数值分析结果表明:两种方法的计算结果一致,验证了解析模型的正确性和可行性.基于分析结果,经选取合适的电机参数,制作了样机,并测试了该电机启动推力变化情况.实验结果和计算结果相符,表明解析模型满足了新型圆筒直线电机的计算要求,同时也验证该方法的可靠性.结果还表明该电机满足了动感雕塑隐蔽驱动的要求.进一步还研究了电机气隙大小、次级厚度等主要结构参数对电机推力等性能的影响,结果显示:气隙增大,推力减小;次级厚度为10mm时,推力为198.51N,达到最大.     

Design and testing of CFRP sleeve for a high-speed permanent magnet synchronous motor with surface-mounted rotor

Journal of Mechanical Science and Technology - A high-speed (HS) permanent magnet (PM) synchronous motor (HSPMSM) with a carbon fiber-reinforced plastic (CFRP) protective sleeve in the...     

一种新型平面研磨机的研制与实验

根据研磨最佳运动学条件,结合现有研磨机,研制了新型行星轮式恒速率变向平面研磨机.研磨机具有被研磨表面各点研磨轨迹相同、速度相同,研磨运动方向恒速率变向的运动特性.利用研磨实验机进行了大量研磨实验,取得了很好的研磨效果,研磨表面Ra可至纳米级.     

Control of a DC motor using algebraic derivative estimation with real time experiments

This paper presents an experimental control scheme for DC motors which combines an overlapping implementation of the algebraic derivative estimation method and a disturbance estimator based on the aforementioned algebraic derivative method. The methodology only requires the measurement of the angular position of the motor and the voltage input to the motor. The main advantages of the proposed approach are: it is independent of the motor’s initial conditions, the methodology is robust to Coulomb friction effects, it does not require any statistical knowledge of the noises that corrupt the data, the derivative estimation process does not require initial conditions or dependence between the system input and output, and the algorithm is computed on-line and in real time. The effectiveness of the proposed controller has been verified by means of computer simulations and it has also been experimentally implemented on a laboratory prototype with excellent results in both, stabilization and trajectory tracking tasks.     

神经网络矢量控制在永磁同步电动机中的应用

在永磁同步电动机(PMSM)矢量控制基本原理分析的基础上,提出了一种基于矢量控制的新型人工神经网络(ANN).人工神经网络用于速度控制和空间矢量脉宽调制(SVM).神经网络速度控制器不依赖于系统精确数学模型,具有动态响应快和稳态精度高的特点;同时基于SVM的人工神经网络算法(ANN-SVM)较易实现,它的计算量小,而且能有效降低谐波干扰.在Matllab/Simulink环境下,建立了一个基于人工神经网络矢量控制的PMSM仿真模型,并对其进行研究.仿真结果证明所提出的基于矢量控制的人工神经网络的可行性和有效性.