GIANT MAGNETOSTRICTIVE ACTUATOR IN SERVO VALVE AND MICRO PIPE ROBOT

Performance of giant magnetostrictive material (GMM) is introduced. Principleof work, basic structure and key techniques of giant magnetostrictive actuator (GMA) are analyzed.Its dynamic models of magneto-mechanical coupling are established. The structure and principle ofthe pneumatic servo valve and the micro pipe robot with new homemade GMM are presented. Theexperiment is carried out under typical working conditions. The experiment results show that the GMMpneumatic servo valve has wide pressure control characteristics, good linearity, and fast responsespeed. The movement principles of the GMM robot system are reliably feasible and its maximal movingspeed is about 8 mm/s. It is preferable to the driving frequency of the robot within 100 approx 300Hz.

Bifurcation and chaos characteristics of hysteresis vibration system of giant magnetostrictive actuator

Chaotic motion and quasi-periodic motion are two common forms of instability in the giant magnetostrictive actuator(GMA).Therefore,in the present study we intend to investigate the influences of the system damping coefficient,system stiffness coefficient,disc spring cubic stiffness factor,and the excitation force and frequency on the output stability and the hysteresis vibration of the GMA.In this regard,the nonlinear piezomagnetic equation,Jiles-Atherton hysteresis model,quadratic domain rotation model,and the GMA structural dynamics are used to establish the mathematical model of the hysteresis vibration system of the GMA.Moreover,the multi-scale method and the singularity theory are used to determine the eo-dimensional two-bifurcation characteristics of the system.Then,the output response of the system is simulated to determine the variation range of each parameter when chaos is imposed.Finally,the fourth-order Runge-Kutta method is used to obtain the time domain waveform,phase portrait and Poincare mapping diagrams of the system.Subsequently,the obtained three graphs are analyzed.The obtained results show that when the system output is stable,the variation range of each parameter can be determined.Moreover,the stability interval of system damping coefficient,system stiffness coefficient,and the coefficient of the cubic stiffness term of the disc spring are obtained.Furthermore,the stability interval of the exciting force and the excitation frequency are determined.

Structure design and characteristics analysis of a cylindrical giant magnetostrictive actuator for ball screw preload

In order to achieve automatic adjustment of the double-nut ball screw preload, a magnetostrictive ball screw preload system is proposed. A new cylindrical giant magnetostrictive actuator （CGMA）, which is the core component of the preload system, is developed using giant magnetostrictive material （GMM） with a hole. The pretightening force of the CGMA is determined by testing. And the magnetic circuit analysis method is introduced to calculate magnetic field intensity of the actuator with a ball screw shaft. To suppress the thermal effects on the magnetostrictive outputs, an oil cooling method which can directly cool the heat source is adopted. A CGMA test platform is established and the static and dynamic output characteristics are respectively studied. The experimental results indicate that the CGMA has good linearity and no double-frequency effect under the bias magnetic field and the output accuracy of the CGMA is significantly improved with cooling measures. Although the output decreased with screw shaft through the actuator, the performance of CGMA meets the design requirements for ball screw preload with output displacement more than 26 μm and force up to 6200 N. The development of a CGMA will provide a new approach for automatic adjustment of double-nut ball screw preload.

DEVELOPMENT OF THE CONTROL METHODOLOGY OF THE GIANT MAGNETOSTRICTIVE ACTUATOR BASED ON MAGNETIC FLUX DENSITY

According to the principle of the magnetostriction generating mechanism, thecontrol model of giant magnetostriction material based on magnetic field and the control method withmagnetic flux density are developed. Furthermore, this control method is used to develop a giantmagnetostrictive micro-displacement actuator (GMA) and its driving system. Two control methods whosecontrol variables are current intensity and magnetic flux density are compared with each other byexperimental studies. Finally, effective methods on improving the linearity and control precision ofmicro-displacement actuator and reducing the hysteresis based on the controlling magnetic fluxdensity are obtained.

Research on Giant Magnetostrictive Actuator for Turning Vibration Control

Magnetostriction is a phenomenon in which a magneti c field is used to produce a change in size of some materials. This property has b een known in elements such as nickel, iron and cobalt. Because the rare-ear th alloy Terfenol-D can offer much larger strains than nickel, iron, cobalt, an d other smart materials such as piezoelectric materials, it is called giant magn etostrictive material. Making use of the giant magnetostrictive material, the gi ant magnetostrictive actuator has higher bandwidth and rapider response than oth er actuators. So it is widely used in active vibration control, especially in lo w frequency stage. In this paper, a turning vibration control system is develope d. The system has an actuator clamped in a flexor that is rigid in the feed and main cutting force directions, yet is flexible in the radial direction. The stru cture of the giant magnetostrictive actuator is developed after magnetic circuit and some structure parameter are calculated. According to the turning frequency , the transient and stable-state output of the giant magnetostrictive actuator is measured. The test result demonstrated that the actuator responses the input rapidly, and the actuator has perfect stable-state and transient output charact eristic. The characteristic includes the stable-state output linearity, repeata bility and transient delay between output displacement and input current.

Experimental Research on Output Performances of Giant Magnetostrictive Actuator

The paper introduces the performances of magnetostrictive actuators and its applications,discusses the design methods for the structure and internal magnetic circuit of a giant magnetostrictive actuator,and makes tests on the output displacement and force characteristics for an actuator using homemade magnetostrictive material.The experimental result shows that the actuator has satisfactory output precisions and ranges in transient and stable states,and can be used in low-frequency vibration control system of precise equipment.

Magnetostrictive and Kinematic Model Considering the Dynamic Hysteresis and Energy Loss for GMA

Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.

Theory and experiment of observer based magnetostrictive self-sensing actuator

Giant magnetostrictive actuators (GMAs) often work in a close-loop feedback system. This system needs independent sensors which may be difficult to be fixed, besides, excessive sensors may cause more unpredicted problems in a large system. This paper aims to develop a self-sensing GMA. An observer based on piezomagnetic equations is constructed to estimate the stress and strain of the magnetostrictive material. The observer based self-sensing approach depends on the facts that the magnetic field is controllable and that the magnetic induction is measurable. Aiming at the nonlinear hysteresis in magnetization, a hys- teresis compensation observer based on Preisach model is developed. Experiment verified the availability of the observer approach, and the hysteresis compensation observer has higher tracking precision than linear observer for dynamic force sensing.

基于Preisach修正模型的GMA前馈补偿研究

超磁致伸缩驱动器(GMA)的磁滞建模与非线性补偿是实现GMA高精度定位的基础。根据GMA的特点,提出了GMA的磁滞Preisach修正模型建模与非线性补偿方法。设计制作了一台GMA样机,对其主磁滞回线和一阶折返曲线进行了精密测量,基于实验数据建立了驱动器的Preisach磁滞修正模型。为了避免对Preisach算子求逆,提出了一种以主磁滞回线升程为基准的输入校正迭代算法,并以此设计了驱动器的前馈补偿器,实验表明,提出的GMA前馈补偿方法具有较高的精度,其定位误差不超过1%。

GMA在脉冲喷射开关阀中的应用

通过分析脉冲喷射开关阀的工作性能,提出致动器是决定脉冲喷射开关阀特性的关键因素.对比3种致动器的性能参数,指出GMA更适合脉冲喷射开关阀的工作要求.GMA的性能分析和仿真结果给出了在脉冲喷射开关阀中工作的GMA的静、动态特性.脉冲喷射开关阀单脉冲流量实验曲线表明:脉冲喷射开关阀的单脉冲流量随励磁电流的变化规律与GMA的磁致伸缩曲线特性相似,在GMA的磁致伸缩曲线的线性区即可满足单脉冲喷射流量要求.动态实验中,脉冲喷射开关阀的阀芯位移阶跃响应上升时间只有0.81 ms,远远满足脉冲喷射开关阀应用的工作频率要求.

基于GMA喷嘴挡板伺服阀的动态特性

提出基于GMA喷嘴挡板伺服阀的新结构,研制了GMM电-机械转换器及其喷嘴挡板伺服阀,分析其结构特点与需要解决的关键技术,建立动态数学模型。构建基于GMA喷嘴挡板伺服阀动态特性的试验系统,试验研究GMA喷嘴挡板伺服阀的阶跃和幅频响应特性,试验测得其阶跃响应上升时间为1 ms、幅频宽达680 Hz;将试验结果与仿真结果进行对比分析,两者基本吻合,论证动态数学模型的正确性。研究结果表明,用GMM设计新型电-机械转换器,可提高喷嘴挡板阀乃至整个电液伺服系统的频响和精度。

基于改进PSO算法的GMA迟滞模型参数辨识

使用改进的粒子群优化算法辨识Jiles-Atherton模型参数。针对J-A模型对超磁致伸缩致动器(giant magnetostrictive actuator,GMA)迟滞特性建模中磁化参数互相嵌套难以辨识的特点,改进磁滞模型并建立了考虑超磁致伸缩材料磁机耦合特性的动态磁滞模型;为了克服普通粒子群算法实际求模型参数时计算量大,运行时间长的缺点,提出基于粒子群算法和遗传算法的改进算法--带交叉因子的粒子群优化算法,将模型仿真所求的磁化强度和实验测得的磁化强度的差值的平方作为适应度函数,并结合最小二乘法思想对J-A模型的几个参数进行辨识;最后,在Matlab 7.0上进行仿真,给出了模型辨识后的结果。在不同预压力和驱动频率下的仿真结果与GMA已有实验数据进行对比,验证得出辨识后的模型可较好地与实验数据拟合,磁致伸缩位移误差在5%以内。

GMA的温度特性分析及热形变被动补偿方法研究

利用超磁致伸缩材料的磁致伸缩效应特性制成的磁致伸缩智能构件,位移输出精度可达亚微米级,这为精密与超精密加工领域提供了新的驱动解决方案,这种精密微驱动过程是依靠智能材料的功能性实现的。然而,在磁致伸缩智能构件工作过程中,线圈的焦耳热损耗、材料磁滞与涡流损耗等因素会导致其温度升高,并伴随着材料出现热变形、磁致伸缩系数不稳定等问题,从而严重影响系统的输出性能。为降低温升对磁致伸缩智能构件工作性能的影响,对超磁致伸缩致动器的温度变化特性进行了深入分析,提出一种热形变被动补偿机构,完成了具有热形变自补偿功能的超磁致伸缩致动器设计。实验结果表明,磁致伸缩致动器的主要发热形式和发热源,取决于激励电流形式、工作频率;所设计的超磁致伸缩致动器在工作过程中能够对热形变自动进行补偿。研究结果为提高磁致伸缩智能构件在精密与超精密驱动领域应用过程中的工作精度提供了一种途径。

基于Preisach理论的GMA迟滞建模与参数辨识

针对一直动型磁致伸缩致动器(GMA)的非线性迟滞建立了数学模型,对限制三角形进行均匀离散网格划分,给出了非负约束最小二乘参数辨识模型,在一阶回转实验数据(FOD)的基础上,得到了GMA迟滞输出预测模型,并采用LabVIEW虚拟仪器平台进行了迟滞预测实验.为减小涡流对实验结果的影响采用了低频信号(1Hz).实验结果表明,用非负约束最小二乘参数辨识算法得到的数值模型对GMA迟滞位移输出有较高的预测精度,预测误差小于6%.进一步的误差分析表明,经典Preisach模型同余性要求与GMM变化率依赖型迟滞之间的差异是预测误差产生的主要原因,必须通过模型的改进,放松其对系统同余性的要求才能够进一步提高经典Preisach模型的迟滞预测精度.

GMA油膜轴承动态控制轴心轨迹的试验研究

介绍了一种基于超磁致伸缩驱动器(GMA)的油膜轴承试验台的工作原理,完成了GMA油膜轴承所支撑转子的轴心轨迹动态控制试验。试验结果表明,选择合适的控制电流和相位差后,该油膜轴承能够动态抑制所支撑转子的工频振动,明显缩小所支撑转子的轴心运动轨迹;对于某控制电流,存在一个能使系统的工频振动幅值最小的最佳相位差;随着控制电流的增大,最佳相位差有增加的趋势。试验结果证实了GMA油膜轴承具有强的轴心轨迹控制功能,能够抑制所支撑转子的振动,具有高的位置精度和旋转精度。

基于通用运放的GMA用大功率恒流驱动源设计

在分析超磁致伸缩材料的驱动特性及超磁致伸缩执行器驱动源特点的基础上,采用连续调整型恒流源的原理,以通用运放为基础,研制出电流在-3^+3A范围内连续可调的大功率恒流功放作为超磁致伸缩执行器驱动源。实际测试的结果表明其性能良好,可以满足驱动超磁致伸缩材料的要求。

GMA再生型颤振系统的稳定性及其控制

综合考虑再生型颤振对工件及超磁致伸缩微致动器的影响,建立了超磁致伸缩微致动器车削颤振系统非线性动力学模型。根据Lyapunov第一次近似稳定性定理及霍尔维茨判据对其进行了稳定性分析及控制研究,讨论了系统参数对GMA颤振系统稳定性的影响。同时采用简单自适应控制方法对颤振系统进行了控制研究。结果表明:车削的极限宽度、工件的质量及其等效刚度对系统的稳定性有明显的影响;简单自适应控制方法可有效抑制再生型颤振对系统稳定性的影响。

基于因素趋势法的GMA磁场研究和仿真分析

为增强超磁致伸缩驱动器(GMA)输出特性,提高超磁致伸缩材料(GMM)棒在磁场下的磁致伸缩性能,根据安培环路定律、基尔霍夫定律、磁通的连续性定律建立GMA磁路模型,推导出GMM棒中心线磁场强度和均匀率与GMA内各结构参数的关系式。在Ansys Maxwell中建立简化的二维平面模型,依据L_(25)(5^(5))正交试验仿真分析,做极差分析、绘制因素趋势图、回归分析和规划求解,得出GMA内各结构参数对最大磁场强度和均匀率的影响。结果表明:GMM棒几何参数、GMA组件材料属性、线圈匝数和电流参数在工程设计约束下,影响GMM棒最大磁场强度和均匀率的主要因素为导磁片半径、导磁片厚度和驱动线圈长度。在多因素多目标决策,采用目标规划法,得到GMA最大磁场强度为40.22 kA/m,均匀率为95.17%。

考虑介电常数影响的GMA内部磁场特性分析

以Maxwell's方程为基础,结合超磁致伸缩材料压磁方程,建立了考虑介电常数、预压应力等参数的超磁致伸缩材料内部磁场径向分布模型,并对其进行了理论分析和数值仿真.讨论了介电常数、预压应力、激励频率等参数对材料内部磁场分布及滞回特性的影响.结果表明,超磁致伸缩材料径向内部磁场分布具有明显的集肤效应和滞回特性;受电导率与介电常数共同影响,材料的磁场分布出现了双峰现象;沿磁致伸缩材料半径增大方向,外激励磁场与材料内部磁场的滞回特性逐渐减弱,磁场损耗随之降低;随着预压应力的增大,材料内部的集肤效应逐渐减小.

GMA喷嘴挡板阀参数设计及特性研究

介绍了GMA喷嘴挡板阀的结构组成和工作原理,设计计算了GMA喷嘴挡板阀的基本参数,推导出了GMA喷嘴挡板阀的压力-流量特性方程。对其控制压力进行了试验研究,试验结果表明:GMA喷嘴挡板伺服阀具有较宽的压力控制特性,可达0.52MPa;较快的响应速度,幅频宽达680Hz。利用超磁致伸缩电-机转换器(GMA)代替传统的力(矩)马达可提高液压控制阀和液压控制系统的响应速度和精度,可满足特殊系统的更高要求。