补偿压电陶瓷迟滞和蠕变的逆控制算法

研究了用于扫描探针显微镜,特别是原子力显微镜(AFM)中的扫描器高精度定位问题。压电陶瓷驱动器通常用于这种扫描器中,在无补偿的开环控制期间,它在输入电压和输出位移之间表现出明显的迟滞和蠕变。迟滞和蠕变降低了扫描器的定位精度并使扫描图像出现了畸变。给出了迟滞和蠕变模型及参数的在线辨识方法。在AFM的扫描控制中,使用基于该模型的逆控制算法补偿了压电陶瓷的迟滞和蠕变。在分析中,Preisach迟滞模型和对数蠕变模型被用于描述压电陶瓷驱动器的非线性。由于该方法不需要在控制过程中进行参数设置,因此很容易使用。此外由于是开环控制方法,可以具有更好的分辨率。闭环操作能够给出较好的迟滞和蠕变补偿,但由于在高带宽情况下传感器动态范围的限制,对于小扫描区域或样本特征,它减小了成像的分辨率。三角波轨迹跟踪的仿真结果说明轨迹误差在传感器噪声量级上,证明了这个方法的有效性。     

超磁致伸缩致动器的小脑神经网络前馈逆补偿-模糊PID控制

针对超磁致伸缩致动器(GMA)在精密致动控制中存在的迟滞和位移非线性,提出了小脑神经网络(CMAC)前馈逆补偿结合模糊PID控制的新策略。通过小脑神经网络(CMAC)学习获得超磁致伸缩致动器动态逆模型用于对超磁致伸缩致动器迟滞非线性进行补偿;利用模糊PID控制降低小脑神经网络(CMAC)学习时的误差和抑制扰动,提高系统的跟踪控制性能,从而实现超磁致伸缩致动器的精密致动控制。仿真和实验结果表明:所采用的控制策略有效地消除了迟滞非线性的影响,系统的跟踪误差降低到了5%以下,而位移跟踪误差均方差仅为0.58。此外,这种策略的特点是学习和控制同时进行,控制系统能够适应被控对象动态特性的变化,使系统具有较强的鲁棒性,同时也能够有效地抑制外界的干扰,提升系统的自适应控制性能。     

PBP驱动器率相关迟滞特性研究及其线性化控制

后屈曲预压缩压电双晶片(Post-buckling pre-compression,PBP)驱动器作为一种大行程压电舵机驱动器,存在着严重的率相关迟滞现象。为了使PBP驱动器能够作为具有较高控制精度的微小型飞行器舵机驱动器,利用基于Bouc-Wen模型的Hammerstein率相关迟滞模型对其进行参数识别,并通过试验验证了该模型能够较好地预测PBP驱动器的率相关迟滞特性;在此基础上为PBP驱动器设计一种具有在线自适应能力的前馈单神经元PID复合线性化控制器,在多种单复合频率信号作用下对其控制回路进行位移跟踪半实物仿真试验,并与基于径向基函数(Radial basis function,RBF)神经网络PID控制器进行对比,结果表明前馈单神经元PID控制器具有更快的响应速度和更高的控制精度。     

Practical and intuitive controller design method for precision positioning of a pneumatic cylinder actuator stage

The present paper describes a practical and intuitive controller design method for precision positioning of pneumatic cylinder actuator stages. Pneumatic actuators are easy to use and have numerous advantages, which has led to these actuators having a wide variety of applications. However, pneumatic actuators have notable nonlinear characteristics, which make precision positioning difficult to achieve. The purpose of the present study is to clarify a practical and intuitive controller design procedure for precision positioning of a pneumatic cylinder actuator. In addition to positioning performance, the present study focuses on the realization of easy controller design without the need for the exact model parameters or knowledge in control theory for general-industrial-use pneumatic cylinder actuators with friction characteristics. These considerations are important in order to fully exploit the advantages of pneumatic cylinder actuators in a wide variety of applications. As such, three elements are added to the conventional continuous-motion nominal characteristic trajectory following (CM NCTF) controller. A new design procedure of the improved CM NCTF controller for pneumatic cylinder actuator stages is introduced, and the positioning performance of the designed control system is examined experimentally under several conditions. The positioning results generally indicate a positioning error of 50 nm, which is equal to the sensor resolution.     

压电陶瓷微动台的复合控制

压电陶瓷微动台的迟滞非线性严重影响其动态定位精度,为了解决这一问题,采用一种改进的PI模型对微动台的迟滞非线性进行了建模.为了提高传统PID算法对压电陶瓷微动台的动态定位性能,将改进的PI模型与传统PID算法组合构成前馈复合控制算法,并进行了微动台的慢速与快速动态定位实验.结果表明,对同频曲线定位时,前馈PID复合算法的最大误差为传统PID算法的40％左右,平均误差为传统算法的20％～30％左右;对多频曲线定位时,前馈PID复合算法的最大误差和平均误差为传统PID算法的33％左右.数据表明前馈PID复合算法的动态定位性能明显优于传统PID算法.     

Adaptive feed-forward hysteresis compensation for piezoelectric actuators

Piezoelectric actuators are often employed for high-resolution positioning tasks. Hysteresis and creep nonlinearities inherent in such actuators deteriorate positioning accuracy. An online adaptive nonlinear hysteresis compensation scheme for the case of symmetric hysteretic responses and certain periodic reference trajectories is presented. The method has low complexity and is well suited for real-time implementation. Experimental results are presented in order to verify the method, and it is seen that the error due to hysteresis is reduced by more than 90% compared to when assuming a linear response.     

压电陶瓷驱动器的滑模神经网络控制

由于压电陶瓷驱动器的迟滞非线性严重影响其定位精度,本文提出了一种滑模神经网络控制方法来改善它的性能.用径向基函数神经网络的输出作滑模控制的等价控制量,由迟滞补偿器估计控射器参数误差、外部扰动和近似计算所造成的不确定量对神经网络的输出控制量进行补偿,从而使驱动器系统状态保持在滑模平面上.基于Lyapunov稳定性理论推导了控制器和补偿器的自适应调节律,分析了控制系统的收敛性和稳定性,以可变幅值的低频三角波为参考位移量对控制系统进行了实验测试与分析,结果表明,只采用神经网络控制时的平均定位误差为0.43 μm,最大误差为0.77 μm,而采用滑模控制方法对神经网络控制量进行补偿后,平均定位误差减小为0.27 μm,最大误差减小为0.49μm,定位精度有了显著的提高.     

Ultra-precise tracking control of piezoelectric actuators via a fuzzy hysteresis model

In this paper, a novel Takagi-Sugeno (T-S) fuzzy system based model is proposed for hysteresis in piezoelectric actuators. The antecedent and consequent structures of the fuzzy hysteresis model (FHM) can be, respectively, identified on-line through uniform partition approach and recursive least squares (RLS) algorithm. With respect to controller design, the inverse of FHM is used to develop a feedforward controller to cancel out the hysteresis effect. Then a hybrid controller is designed for high-performance tracking. It combines the feedforward controller with a proportional integral differential (PID) controller favourable for stabilization and disturbance compensation. To achieve nanometer-scale tracking precision, the enhanced adaptive hybrid controller is further developed. It uses real-time input and output data to update FHM, thus changing the feedforward controller to suit the on-site hysteresis character of the piezoelectric actuator. Finally, as to 3 cases of 50 Hz sinusoidal, multiple frequency sinusoidal and 50 Hz triangular trajectories tracking, experimental results demonstrate the efficiency of the proposed controllers. Especially, being only 0.35% of the maximum desired displacement, the maximum error of 50 Hz sinusoidal tracking is greatly reduced to 5.8 nm, which clearly shows the ultra-precise nanometer-scale tracking performance of the developed adaptive hybrid controller.     

液压驱动Stewart平台非线性自适应控制器设计

电液驱动Stewart平台具有高度非线性特性,且各个通道之间存在严重的负载交联耦合,影响了仿真模拟器运动的平滑性和逼真度.以往这种系统的控制器大都是以驱动分支作为被控对象进行设计的,忽略了各个通道之间负载交联耦合的影响,导致系统控制精度的降低,严重时甚至可能造成系统的不稳定.针对上述问题,提出以动平台为被控对象,根据动平台动力学方程设计一种基于加速度鲁棒观测器的非线性自适应控制器的方法,通过Lyapunov方法证明该控制算法具有渐进稳定性.试验表明提出的控制算法在提高平台控制精度和抑制通道间负载交联耦合方面的效果较理想.     

压电陶瓷驱动器蠕变特性的研究

压电陶瓷驱动器具有位移分辨率高、体积小、响应快、输出力大、不发热等优点，但其固有的迟滞、蠕变和非线性，严重影响了它的定位精度。在大行程微动工作台中，需要借助于位移放大机构来克服压电陶瓷驱动器位移行程小的缺点，但放大机构在放大位移的同时，也放大了压电陶瓷蠕变和迟滞误差的影响。本文通过对一种大行程压电陶瓷微动工作台蠕变特性的研究性实验，得到了该机构的蠕变特性曲线，找到了压电陶瓷驱动器蠕变的规律，为进一步修正和减少蠕变误差的影响、提高系统的定位精度，提供了科学的依据。     

压电陶瓷执行器的神经网络实时自适应逆控制

目的：为了提高压电陶瓷执行器执行精度,提出消除压电陶瓷的非线性、非光滑的迟滞特性的方法。 方法：提出了基于内积的压电陶瓷动态神经网络非线性、非光滑的迟滞逆模型,采用反馈误差学习方法,避免了求取压电陶瓷的Jacobian信息,快速地在线得到压电陶瓷的逆模型,并结合PID反馈控制,在dSPACE系统平台上,实现压电陶瓷的神经网络自适应逆控制,为了提高实时性,程序采用效率高、速度快的C-MEX S Function编程。结果：实验结果表明：神经网络自适应逆控制的控制精度为：0.13μm,而PID控制精度为：0.32μm 。结论：所提出方法有效地消除了迟滞的影响,控制精度高。     

Precision position control using combined piezo-VCM actuators

This paper presents the control performance of a high-precision positioning table using the hybrid actuators composed of the piezoelectric (PZT) actuators and voice-coil motors (VCMs). The combined piezo-VCM actuator features two main characteristics, i.e., a large operation range due to the long stroke of VCM, and a high precision and heavy load positioning ability due to the actuation of PZT impact force. In this paper, a one-degree-of-freedom (1-DOF) experimental setup was configured to examine the control performance and the parametric identification for the VCM was performed based on the recursive-least-square (RLS) method. The control performance was effectively demonstrated by using a switching controller configured by an integral variable structure controller (IVSC) for the VCM to conduct rough position control and an impact force controller (IFC) for the PZT actuator to conduct fine position control. The experimental results showed that the positioning table having mass 881 g was successfully positioned within the positioning accuracy of 10 nm by both the forward and backward positioning processes. In the forward control, it totally took 1.253 s for the sliding table to reach the target position of 450 μm; in the backward control, it took 1.387 s for the sliding table moving from the position of 450 μm to the target position of 200 μm.     

含磁滞补偿的电液伺服系统预设性能跟踪控制

针对电液伺服系统普遍存在的参数不确定性、不确定非线性(磁滞、摩擦、外干扰等),提出一种基于自适应鲁棒控制的含磁滞补偿的预设性能跟踪控制策略。以阀控单出杆液压缸位置伺服系统为例,首先建立了含磁滞非线性的系统数学模型,然后通过定义预设性能函数,实现了对跟踪误差收敛速率、最大超调量和稳态精度的预先规划,基于规划后的转换误差设计了自适应鲁棒控制器,并提高了稳态和瞬态跟踪性能。仿真对比结果表明：该控制策略可以减小磁滞对系统跟踪精度的影响,提高跟踪误差的收敛速度,减小最大超调量,最终实现优良的跟踪性能。     

具有迟滞和蠕变特性压电作动器的模糊自适应逆控制方法

针对具有迟滞和蠕变特性的压电作动器非线性模型,提出了一种前馈控制和反馈控制相结合的自适应模糊逆控制方案。在前馈控制器中压电作动器的迟滞和蠕变非线性特性的逆模型由自适应模糊逻辑系统近似;在反馈控制器中比例控制器用来调节压电作动器的输出误差。该方法可以实时补偿压电作动器的迟滞和蠕变特性,减少作动器跟踪误差。仿真计算结果表明了该方法的有效性。     

压电陶瓷驱动系统及控制方法研究

给出了一种压电陶瓷驱动系统的控制方法,利用VB中的Timer控件和压电陶瓷电源的DLL动态连接库函数,实现了控制电压的实时可编程输出。针对压电陶瓷驱动器的非线性和迟滞特性,应用MATLAB分别拟合出压电陶瓷驱动器在往返行程中电压与位移值的多项式拟合曲线,得到了电压与位移的关系式,为进一步修正和减少非线性及迟滞误差的影响、提高系统的定位精度,提供了分析的依据。     

超磁致伸缩致动器的广义预测-多模PID控制

为了克服超磁致伸缩致动器的磁滞现象对精密驱动定位精度的影响,在进行磁滞补偿的前提下,研究了自校正PID控制方法,提出了基于广义预测控制的广义预测-多模PID控制方法。介绍了广义预测控制的主要思想,并由此导出PID参数与被控对象待估参数的关系,实现了广义预测PID控制;针对起动阶段控制效果不平稳的问题,提出了多模PID控制模式转换条件;最后,根据PID参数变化情况,建立致动器的多模PID控制方法,实现广义预测PID与常规PID的在线控制模式转换与控制。实验结果表明,采用广义预测-多模PID控制器,虽然单次平均运算时间比广义最小方差-模糊PID控制器长7ms,但跟踪误差均方差减少了0.066μm;同时改善了起动平稳性。提出的控制方法能有效消除由扰动带来的影响,提高跟踪精度,改善起动平稳性,适用于对实时性、控制精度要求较高的精密定位领域。     

Precision tracking control of a piezoelectric-actuated system

In this paper, precision tracking control of piezoelectric-actuated systems is discussed. In order to obtain precision tracking control, a modified Prandtl–Ishlinskii (MPI) model is used to model the hysteresis nonlinearity. Then, the inverse MPI model is used to reduce the hysteresis nonlinearity, and a sliding-mode controller is used to compensate for the remaining nonlinear uncertainty and disturbances. In general, the piezoelectric-actuated system can be modeled as a linear model coupled with a hysteresis. When the linear model is identified, it is used to design the sliding-mode controller. Finally, this design method is applied to the motion control of a nano-stage, and experimental results are presented to verify the usefulness of this method.     

用于光阑的旋转型驻波压电作动器

为了驱动光阑实现对光束的控制和调节,提出一种新型的旋转型驻波压电作动器。现有压电作动器中,性能稳定的多为单一振子复合模态工作方式,要求各工作模态频率差小,除了对加工精度要求高之外,由于工作磨损对各模态频率影响不同,工作模态的频率差增大,使作动器的性能和效率下降。针对这一问题和光阑的工作特点,研制了一种新型的旋转型压电作动器。该作动器利用两个相同结构杆形压电振子的同形模态,经摩擦驱动光阑活动环转动,达到调节光阑孔径的目的。原理样机实验表明:当预压力为8N时,在驱动电压为200V_(p-p)～400V_(p-p)范围内,作动器的旋转速度与电压成正比,最大的逆时针旋转速度为75.36rad/min,最大的顺时针运动速度为62.8rad/min;在驱动电压为400V_(p-p)下分辨率可以达到0.34mrad。该压电作动器满足了光阑光束控制的要求,具有结构简单、响应快速、调速平稳和精度高等优点。     

Hybrid controller of a linear piezoelectric walking stage relying on stack/shear piezoelectric actuators

This paper proposes a hybrid control strategy of a novel linear piezoelectric walking stage based on two sorts of piezoelectric actuators, which takes the load variation into account. The proposed stage consists of two parallel 4-bar lever amplification mechanisms with flexure hinges actuated by piezoelectric stacks to heighten the vertical distance (that is more tolerable to the assembly discrepancy), two compression springs (that is able to maintain a fixed linear position without powering), and two shear piezoelectric actuators (that can achieve longer and equivalent to walking motion) in a small form factor. The proposed stage has two operating modes, namely a coarse positioning mode with a more extensive travel range and a fine positioning mode with a nanometer-level resolution, to possess excellent performance for the linear piezoelectric walking stage of load variations. One multimodal switching controller and one feedforward-feedback controller conduct the coarse mode and fine mode, respectively. The optimal frequency for a specific load is obtained through a backpropagation neural network in the multimodal switching control. In the feedforward-feedback control, the inverse mathematical model based on the Bouc-Wen hysteresis model is used to mitigate the hysteresis effect in the feedforward part while the proportional–integral–derivative controller in the feedback part handles the external system disturbances. Experimental results show the proposed hybrid coarse/fine mode control strategy's effectiveness to satisfy an efficient and accurate positioning task.     

压电陶瓷微位移器件控制模型的研究

从不同角度介绍了压电陶瓷微位移器件的两种控制模型.首先,借助于统计物理学分析,结合数学建模方法,建立了一个简单实用的压电陶瓷的迟滞数学模型.其次,借助于弹性体变形理论,介绍了压电/电致伸缩陶瓷的归一化控制模型,从理论上说明了采用电极化强度的方法可以有效减小迟滞的观点.并设计了两种实验系统,对两种控制模型进行了实验验证,实验结果表明,所建立的两种模型可有效减小压电陶瓷的迟滞非线性误差,提高压电陶瓷微位移的控制精度,有助于实现压电陶瓷驱动器的高精度开环微位移控制.