柔性压电式微位移机构动态特性的实验研究

设计了一种压电式微位移机构,采用对称杠杆式柔性铰链放大机构对压电陶瓷输出位移进行放大,弥补了压电陶瓷位移行程过小的缺点.对微位移机构力学模型和压电陶瓷驱动器的动态特性进行了分析,指出压电陶瓷驱动器动态响应的迟滞非线性是影响压电式微位移驱动器控制性能的一个关键因素,直接关系到控制精度的提高,必须采取适当的控制算法予以修正.采用前馈控制同数字PID控制相结合的复合控制算法对柔性压电式微位移机构的控制过程进行校正补偿,建立了动态特性的闭环校正控制系统.实测结果表明,机构的动态响应时间显著缩短,实现了机构的快速响应.     

新型柔性放大机构的动力学前馈复合控制方法

纳米级精度微位移驱动与控制通常使用压电陶瓷驱动器驱动柔性机构来实现.但是压电陶瓷驱动器行程较小,需要使用柔性放大机构对其位移进行放大,并且压电陶瓷驱动器存在蠕变和迟滞等非线性特性,而这些非线性特性极大影响了其输出位移经放大机构放大后的运动精度.针对以上两点,将传统桥式机构的4条桥臂用Scott-Russell机构代替,设计了一种新型柔性放大机构.同时,采用基于动力学逆模型前馈控制与PID反馈控制相结合的复合控制策略,提升放大机构的控制带宽和运动精度.实验结果表明,复合控制策略在1 Hz输入频率下的均方根跟踪误差相较传统PID反馈控制降低了33％,在10 Hz下降低了73％,说明了基于动力学逆模型前馈控制同PID反馈控制相结合的复合控制能够大幅度提高放大机构的跟踪精度.     

压电陶瓷驱动器迟滞非线性的改善方法

压电陶瓷驱动器在微位移定位方面被广泛应用,但压电陶瓷驱动器的迟滞非线性严重影响其定位精度,因此,介绍了各种改善压电陶瓷驱动器迟滞非线性特性的方法,并提出了用3次样条插值法和最小二乘曲线拟合法来实现压电陶瓷驱动器的精确定位,改善压电陶瓷驱动器的迟滞非线性特性,实验表明,以上方法可使压电陶瓷驱动器的定位误差小于5％.     

压电陶瓷迟滞建模及控制仿真

为了提高压电陶瓷驱动器在调节光学谐振腔长度时的精度,设计了一种压电陶瓷驱动系统。同时,为了改善压电陶瓷的迟滞特性,利用Duhem迟滞模型对其进行建模,利用梯度下降法对模型参数进行辨识,得到迟滞模型;并利用逆模型补偿及比例、积分、微分(PID)复合控制方法进行控制。实验结果表明,Duhem模型可以有效地拟合压电陶瓷驱动器的迟滞,在15μm的范围内,最大拟合误差小于0.2μm;同时,在复合控制下,驱动器的最大控制误差为12nm,表明该复合控制方法的有效性。     

压电陶瓷迟滞建模及控制仿真

为了提高压电陶瓷驱动器在调节光学谐振腔长度时的精度,设计了一种压电陶瓷驱动系统。同时,为了改善压电陶瓷的迟滞特性,利用Duhem迟滞模型对其进行建模,利用梯度下降法对模型参数进行辨识,得到迟滞模型;并利用逆模型补偿及比例、积分、微分(PID)复合控制方法进行控制。实验结果表明,Duhem模型可以有效地拟合压电陶瓷驱动器的迟滞,在15 μm的范围内,最大拟合误差小于0.2 μm ;同时,在复合控制下,驱动器的最大控制误差为12 nm,表明该复合控制方法的有效性。     

压电陶瓷驱动器迟滞建模与自适应控制

为了降低压电陶瓷驱动器的迟滞非线性,提出了改进型的Maxwell slip模型并引入自适应控制,使压电驱动器在宽频带下有良好的迟滞补偿效果。在经典Maxwell slip模型中,输出力与输入位移的关系会出现迟滞现象,表现为平行四边形,与压电陶瓷驱动器的迟滞特性接近。由于每一单元滑块的最大静摩擦力与弹簧弹性系数成比例关系,若弹簧系数取定值时,每一个单元的最大静摩擦力在系统实时控制中是不变的,因此可以采用自适应控制算法对输出信号权值进行更新,从而更精确地补偿压电陶瓷驱动器。为了验证该模型,搭建了悬臂梁结构压电实验平台,运用该迟滞模型进行迟滞补偿控制,实验结果表明,对于Maxwell slip模型自适应控制,在0.1~20 Hz宽频带下的均方根误差(RMSE)和绝对平均误差(MAE)均有减小。其中,在0.1 Hz下无前馈补偿控制的RMSE为0.037 5 μm,而通过自适应控制可以将压电微定位平台的RMSE降低到0.012 4 μm以内。与经典模型相比,所提出的Maxwell slip模型自适应控制具有在宽频带内进行精密定位的优点。     

压电驱动器迟滞特性的Preisach模型研究

压电驱动器的迟滞特性是影响其位移输出精度的主要因素。该文采用改进的Preisach模型对压电驱动器的迟滞特性进行建模，并进行了相应的实验研究。实验结果表明该模型可以很好地预测压电驱动器在经过一定的控制电压序列以后的位移输出值．能够有效地降低迟滞特性对压电驱动器位移输出精度的影响。     

压电陶瓷驱动微进给刀架的迟滞建模

以对称式微位移缩小机构和柔性铰链相结合,压电陶瓷驱动的微进给刀架可实现精密加工,但刀架的迟滞特性影响其定位精度。该文根据非线性Preisach模型的理论知识及压电陶瓷驱动微进给刀架的电压位移特性,将模型进行修改后得到刀架迟滞特性的数学模型,并对数学模型式进行离散化处理。实验结果表明,改进后的迟滞模型形式简单,数据采集简便,模型描述精确,能较好地实现压电驱动微进给刀架的迟滞建模,提高了迟滞模型的实用性。为提高压电陶瓷驱动微进给刀架的定位精度,实现精密控制打下基础。     

压电式微位移机构动态特性研究

压电陶瓷驱动器在较高电场的作用下将产生严重的非线性,从而影响其定位精度。压电陶瓷驱动器的非线性不仅与材料的非线性、蠕变、滞后等因素有关,还与器件的动态响应特性有关。动态响应的迟滞非线性是影响压电式微位移驱动器控制性能的一个关键因素,直接关系到控制精度的提高。该文采用前馈控制同数字比例、积分和微分环节(PID)控制相结合的复合控制算法对一维压电式微位移机构的控制过程进行校正补偿,建立了动态特性的闭环校正控制系统。实测结果表明,机构的动态响应时间显著缩短,实现了机构的快速响应。     

双向二维快速伺服刀架的前馈控制研究

以压电陶瓷驱动器作为动力输入的快速伺服刀架具有输出力大和高频率响应的优点。压电陶瓷驱动器固有的迟滞现象严重影响了快速伺服刀架的输出定位精度。为解决此问题,通过引入归一化Bouc-Wen模型建立前馈控制补偿器,归一化Bouc-Wen模型解决了经典Bouc-Wen模型中存在的参数冗余问题。获得模型参数后,基于其逆模型搭建了前馈补偿器,并在搭建的实验平台上进行了单/双自由度轨迹跟踪性能测试。实验结果表明,对于等幅正弦波信号,经前馈控制环节补偿下快速伺服刀架的最大轨迹跟踪误差为1.18%,最大轨迹跟踪偏差为2.61%,证明该文所提出的前馈控制补偿器能提高快速伺服刀架的定位精度。     

压电柔性结构形状复合控制方法研究

以宏纤维复合材料(MFC)驱动柔性悬臂结构为研究对象,着重开展其动态形状控制理论研究。基于有限单元法、均匀化理论和载荷比拟方法,建立了压电驱动层合结构力 电耦合动力学方程,并结合模态降阶法得到其状态空间形式控制模型。同时,针对压电材料作动器迟滞蠕变非线性特征对控制精度影响严重的问题,开展了依据实验数据的迟滞蠕变建模及其前馈逆补偿控制方法的研究,并构建了面向压电驱动柔性结构动态形状控制的迟滞 蠕变前馈补偿与自抗扰反馈控制相结合的复合控制系统。结果表明,该复合控制法能够在保证系统稳定性的前提下有效提高系统动态形状控制精度。     

Novel models for one-sided hysteresis of piezoelectric actuators

The hysteretic behavior of a plant with a non-negative input, referred to as one-sided hysteresis, is characterized by an initial ascending curve and hysteresis loops. It is observed that the widely-used classical Preisach hysteresis model and its modifications cannot represent such one-sided hysteresis due to the limitation of the Preisach hysteresis operator. To address this issue, a novel hysteresis operator modified from the Preisach hysteresis operator is proposed in this study and on this basis, a rate-independent hysteresis model and a rate-dependent hysteresis model are developed with methods to estimate their parameters. An algorithm to invert the rate-independent hysteresis model and its application to tracking control are also presented. The models and control schemes developed were verified experimentally on a commercially-available piezoelectric actuator. The results obtained show that the models developed are promising to represent the one-sided hysteresis of the piezoelectric actuator and that the inverting algorithm of the rate-independent hysteresis model is effective as applied to the tracking control of piezoelectric actuators.     

超精密机床的压电作动器隔振系统研究

压电作动器是振动主动控制中最常用的一种执行机构。文章分析了各种压电作动器的特点及应用范围 ,并用压电陶瓷作动器对超精密机床实施振动主动控制。结果表明 ,该系统应用控制器克服了压电元件的迟滞特性、蠕变特性和非线性后 ,能有效的控制地基振动对超精密机床的影响 ,提高了超精密机床的加工精度     

基于GRU神经网络的晶圆测试工艺控制方法

压电驱动器位移输出的非线性特性,如迟滞的记忆特性及速率相关性,使压电驱动器的建模与控制较难。该文提出了一种基于门控循环单元(GRU)的新型位移输出控制方法。建立相应的位移输出实验平台来验证和分析压电驱动器的滞后现象。使用GRU模拟滞后的内存特性及采用两个全连接层来模拟速率依赖性。该模型是一个端到端系统,其中压电陶瓷和位移放大机构被视为一个整体。针对不同电压输入预测的输出位移量表明,该模型对速率相关的滞后具有很强的泛化能力。使用相同的循环神经网络结构构建逆模型,并进行实验测试。实验结果表明,所提出的位移输出控制法有效地削弱了压电驱动器的非线性特性,有利于将线性系统控制法与前馈补偿法相结合。     

Tracking control of a piezoceramic actuator with hysteresis compensation using inverse Preisach model

This paper presents the classical Preisach hysteresis modeling and tracking control of a curved pre-stressed piezoceramic patch actuator system with severe hysteresis. The actuator is also flexible with very small inherent damping. It has potential applications in active antennas. A series of tests are conducted to study the hysteresis properties of the piezoceramic actuator system. The numerical expressions of the classical Preisach model for different input variations are presented. The classical Preisach model is applied to simulate the static hysteresis behavior of the system. Higher order hysteresis reversal curves predicted by the classical Preisach model are verified experimentally. The good agreement found between the measured and predicted curves showed that the classical Preisach model is an effective mean for modeling the hysteresis of the piezoceramic actuator system. Subsequently, the inverse classical Preisach model is established and applied to cancel the hysteresis the piezoceramic actuator system for the real-time microposition tracking control. In order to improve the control accuracy and to increase damping of the actuator system, a cascaded PD/lead-lag feedback controller is designed with consideration of the dynamics of the actuator. In the experiments, two cases are considered, control with major loop hysteresis compensation, and control with minor loop hysteresis compensation. Experimental results show that RMS tracking errors are reduced by 50% to 70% if the hysteresis compensation is added in the feedforward path in both cases. Therefore, hysteresis compensation with the feedback controller greatly improves the tracking control accuracy of the piezoceramic actuator.     

压电自感知柔性悬臂梁振动控制系统研究

将压电悬臂梁系统离散化的状态空间方程作为预测模型,设计了预测函数控制器.采用电桥电路法分离出压电自感知执行器的感知信号,经过预测函数控制器处理后输出的控制信号作用于自感知执行器,产生相应的执行力来抑制悬臂梁的振动,从而达到振动控制的目的.仿真结果表明,所设计的振动控制系统对柔性悬臂梁振动抑制是非常有效的.     

Tracking position control of piezoelectric actuators for periodic reference inputs

The hysteresis characteristic is one of the major setbacks in precise tracking position control of piezoelectric actuators. In this paper, a position control method for a piezoelectric actuator is presented. The controller is based on PID control method augmented with feedback linearization loop. The feedback linearization loop uses a plant model drawn from the Maxwell slip model. The control strategy is then further extended to include a repetitive control algorithm for tracking periodic inputs. Experiments were performed on a 2-axis linear positioner driven by piezoelectric actuators. The experimental results show that the tracking performance is noticeably improved by augmenting a PID controller with both feedback linearization loop and a repetitive controller.     

Inversion-free force tracking control of piezoelectric actuators using fast finite-time integral terminal sliding-mode

The major hurdles to control the force created by piezoelectric actuators (PEAs) are originated from its strong nonlinear behaviors which include hysteresis, creep, and vibration dynamics. To achieve an accurate, fast and robust force tracking performance without using complicated modeling and parameter identification of PEAs, this paper presents a practical direct force control scheme. The proposed controller is based on two core approaches: 1) fast finite-time integral terminal sliding mode (FFI-TSM) which allows fast convergence and high accuracy to the closed-loop system without control chattering; and 2) an inverse-model-free compensation, named force-based time-delayed estimation (FBTDE) which offers significant robustness with minimum use of plant dynamics information. The finite-time stability of the overall closed-loop system is proven through the Lyapunov’s method. The proposed force tracking controller is implemented on the PEA system driving a variable physical damping actuator mechanism. The overall accuracy, convergence speed, and robustness of the proposed controller are validated under various experimental scenarios. Comparative experimental results are particularly presented to verify the effectiveness of the FFI-TSM term and the FBTDE term.     

Vibration control of a single-link flexible manipulator using an array of fiber optic curvature sensors and PZT actuators

This paper presents a novel distributed sensing and actuation approach for actively suppressing vibrations within flexible link manipulators. Through vibration suppression, the method acts to regulate the shape of flexible links and, consequently, improves the performance of any independent trajectory controller being employed over the manipulator joints. To demonstrate the approach, a series of piezoceramic actuators (PZTs) are bonded to the surface of a single-link flexible manipulator. Slewing of the flexible link induces vibrations in the link that persist long after the hub stops rotating. The vibration suppression is achieved through a combined scheme of PD-based hub motion control and a PZT actuator controller that is a composite of linear and angular velocity feedback controllers. A Lyapunov approach is used to synthesize the composite controller, and a unique, commercially-available sensor, called ShapeTape^?, that provides the linear and angular velocity feedback. The sensor array is comprised of a series of fiber optic curvature sensors that are laminated on a long, thin ribbon tape which can be embedded into the flexible link and measures the bend and twist of the link’s centerline. Simulation and experimental results show the effectiveness of the proposed approach and the ability of the new sensor to provide the requisite feedback.