【作者】 张旭辉；

【导师】 付永领；

【作者基本信息】 北京航空航天大学 ， 机械电子工程， 2008， 博士

【摘要】 随着主动隔振控制技术的发展,对作动器的要求越来越高,这催生了智能材料作动器的诞生和发展。利用超磁致伸缩材料制作的作动器具有许多优越的性能,但其自身也存在一些比较突出的缺点,如非线性,磁滞现象,发热现象等问题,这大大阻碍了其实际应用,所以本文从分析超磁致伸缩机理入手,从以下几方面对作动器进行优化设计:1)利用作动器导磁内壁和端盖及超磁致伸缩材料棒构成闭合磁路,同时在超磁致伸缩材料棒两端放置导磁片,从而使其所处磁场更加均匀;2)合理选择偏置磁场强度及驱动磁场强度,以提高作动器输出的线性度,并降低作动器输出位移中的倍频分量;3)为超磁致伸缩材料施加预压力以提高其伸缩率,并对预压弹簧刚度进行优化计算;4)对驱动螺线管进行优化设计以提高作动器工作效率;5)为了减小涡流效应,对超磁致伸缩材料棒结构进行优化设计,采用多片结构方案;6)用肋片散热代替水冷方式,使作动器的应用更加灵活,方便;7)对作动器进行磁屏蔽,减小其对周围设备的干扰。在完成了作动器优化设计之后,对基于超磁致伸缩作动器的隔振原理进行了透彻分析,提出了其实质是位移跟踪的看法,并和传统的力控制进行了对比,仿真结果表明,位移跟踪模型无论在稳定性上还是稳态误差上都优于力控制模型。以此为根据,建立了主被动联合隔振平台的控制模型,并分析了被动隔振元件性能参数对系统整体隔振性能的影响。在控制算法方面,本文在最小均方自适应(LMS)算法基础上进行改进,主要目的是提高控制算法稳定性。为此提出了一种基于归一化LMS的约束权函数算法,该算法兼有变步长LMS和约束权函数的优点。在主动隔振系统中,次通道的影响不容忽视,通常做法是对其进行在线辨识,但辨识所用的白噪声同时进入到了误差信号中,从而会破坏系统性能,所以本文在滤波Fx_LMS算法的基础上进行改进,从误差信号中剥离用于辨识的白噪声信号,从而提高辨识精度并改善控制系统性能。另外,目前人们在研究控制算法时很少注意控制器实际输出能力的问题,这可能会导致在实际工作中元器件的烧毁,而如果为了保护元器件进行简单的限幅的话,会在系统中引入高频噪声,所以本文提出了一种误差约束自适应控制算法,该方法的中心思想是对反馈信号进行约束,即不使控制算法收敛到最优值,仿真表明该方法在保护系统元件的同时不会产生高频噪声。为了对上面所做工作进行验证,本文首先利用现有元器件进行了控制算法的试验。在试验中,利用信号发生器模拟平台振动,然后控制作动器输出位移跟踪该振动信号,并利用位移传感器检测作动器实际输出位移。试验结果表明本文提出的算法可以实现对周期信号的控制且性能较稳定。然后为了验证本文提出的隔振模型和控制算法,根据压磁-压电比拟法并利用ANSYS软件对超磁致伸缩作动器进行了静态仿真和谐性仿真,结果表明本文提出的作动器优化设计方法比较合理,利用该原理设计的作动器性能比较理想。最后,利用UG、MATLAB和ADAMS软件搭建了基于超磁致伸缩作动器的虚拟隔振平台,并利用其进行控制算法和系统模型的仿真验证。结果表明本文所建模型简单,实用;所提算法均能够实现振动的隔离,而且较为稳定,可为工程实际应用提供借鉴。更多还原

【Abstract】 With the advancement of active control on vibration, higher demands on actuator catalyze the creation and development of intelligent materials. Due to its giant magnetostrictive strain, high power density, high electromechanical coupling coefficient and high response speed, the giant magnetostrictive actuator (GMA) has been widely concerned in the field of intelligent actuator by researchers in China and abroad. However, there’re also many disadvantages which challenge its actual application, such as nonlinearity, hysteresis and radiation. Based on the analysis of the giant magnetostrictive phenomenon and its form mechanism, research of optimization design which could improve the performance of the GMA are processed as follows:1) Magnetism material is used to make the inner wall and the two tips of GMA in order to form a closed loop around the giant magnetostrictive material (GMM) rod. Two pieces of magnetizer are placed at each end of GMM to proportion the distribution of magnetic field in GMA and reduce the leakage of magnetism.2) Methods of selecting the intensity of pre-magnetic field and drive magnetic field are discussed to increase linearity and to eliminate frequency multiplication in GMA.3) Pre-pressure is applied to GMM by a spring to improve the ratio of expansion, and the rigidity of the spring is optimized.4) The shape of the drive solenoid is optimized to enhance the work efficiency of GMA.5) GMM is cut into small slices along the axes so that the whirlpool effect is weakened.6) The traditional water cooling controlling system is replaced by configuration with rib, which makes the application of GMA more flexible and convenient.7) To reduce the disturbance to other equipments around it, GMA is shielded with non-magnetism material.Principles of vibration isolation (VI) are intensively analyzed after finishing the optimization design of GMA. An opinion that the essential of VI here is displacement tracking is proposed, which is compared with traditional force control. Then the model of VI platform is established based on displacement tracking, and how the parameters of passive VI affects the VI capability of the whole system is discussed. Simulation results show that displacement tracking has better performance of stability and less steady-state error than force control does.About control arithmetic, a new arithmetic of constraint weight function based on normalized LMS which originates from minimum mean square adaptive LMS is raised in order to improve the stability of system. This new arithmetic has both the advantages of changeable step LMS and constraint weight function. In the active vibration isolation system, the effect of secondary path is very important, and it’s usually solved by using on line identification. But the white noise used in the identification enters into the error signal which would damage the performance of the system. In this dissertation the white noise is separated from the error signal by using improved Fx-LMS arithmetic to increase the identification precision and system capability.Furthermore, the actual output ability of the controller is often neglected by people while doing researches on control arithmetic, this could make the elements burnt while in practice. But high frequency noise will be brought in if simply using slicing to protect the elements. A new error constraint adaptive control arithmetic is proposed in this dissertation to solve those problems above, which could restrict the feedback signal to make system achieve a non-zero convergence. Simulation results show that this method could protect the elements without bringing in high frequency noise.Experiments are done with the equipments available about control arithmetic in order to validate the ideas and simulations above. Signal generator is used to simulate the vibration of the platform, and the displacement outputs of the actuators are controlled to follow the vibration signal, while the actual displacements of the actuators are tested by displacement sensors. Simulation results show that the arithmetic proposed in this paper could control the periodic signal and has a good stability.Next, both static and compatible simulations of GMA are done by piezoelectric- piezomagnetic analogy, mainly using ANSYS. Results show that the design of the actuators here is proper as the performance is good.Last, after finishing the capability checkout of the actuator, a virtual vibration isolation platform based on GMA is built using UG, MATLAB and ADAMS, and simulations of the proposed algorithms and the system model are done on this platform for proof. Results show that the model is simple and effective and the arithmetic proposed in the paper could implement the vibration isolation and also has a good stability, so it might be used for reference in engineering application.更多还原