A simplified quasi-static computational model for self-sensing applications of magnetostrictive actuators based on terfenol-D rods is presented. Paths and angle changes in the magnetic moments rotation of Tb0.3Dy0.7Fe2 alloy are studied as functions of compressive stress and magnetic field, and then used to determine the magnetization in its actuation. Then sensing of magnetic induction picked from a driving coil in an actuator is derived. The model is quick and efficient to solve moments rotation and its magnetization. Sensing results of compressive stress and magnetostriction calculated by the model are in good agreement with experiments and will be helpful in the design and control of self-sensing applications in actuators.
为了同时实现应用于步进扫描投影光刻机中的长行程直线电机的高推力密度、低推力波动和低铜损耗,提出了基于多种群遗传算法(multiple population genetic algorithm,MPGA)的环形绕组形式无铁心永磁直线同步电机(air-corepermanent magnet linear synchronous motor,ACPMLSM)多目标优化设计方法。在建立磁场分析模型的基础上,推导了关键参数的解析表达式。以永磁体、环形绕组的尺寸为变量,以推力体积比、电机常数和推力波动为优化目标,提出了基于权重系数的多目标优化函数,应用搜索能力强、收敛速度快的多种群遗传算法优化电机的结构尺寸。结果表明,在不同的权重系数下,MPGA得到的电机优化设计结果与设计目标具有良好的一致性。有限元仿真和实验结果证明了所提方法的有效性和可行性。
Direct-drive actuators,linear motors are widely used in many industrial and military applications,particularly in high-end manufacturing due to advantages of high force density,rapid dynamic response,and low thermal losses.Permanent magnet linear synchronous motors(PMLSMs)can dramatically improve the dynamic and static performance of the motion system.However,as one of the most critical sources of error,the thrust ripple of linear motors can deteriorate performance and even excite the mechanical resonance.Thrust ripple suppression technology had received broad interest and has been researched extensively.Therefore,this paper summarizes different types of thrust ripple suppression methods and their principles are analyzed in detail.Firstly,structural optimization methods are introduced to suppress the thrust ripple and increase the precision of the thrust.Secondly,control methods are described to decrease the velocity fluctuation caused by the thrust ripple.Thirdly,a combination of structural design and control method is presented to compensate the ripple,meaning high order harmonic components are eliminated by permanent magnets(PM)skewing technology and low order harmonic are compensated by a linearization observer.Finally,conclusions are made regarding thrust ripple suppression technology and the future trend is proposed.
