WTYD型压电陶瓷微位移器的迟滞特性建模与实验验证

为了模拟WTYD型压电陶瓷微位移器的输出位移与驱动电压之间的迟滞曲线,通过采用Bouc-Wen模型模拟迟滞分量,提出了一种表征WTYD型压电陶瓷微位移器的输出位移与驱动电压之间迟滞关系的Bouc-Wen模型并建立了相应的参数辨识方法。为了验证Bouc-Wen模型及其相应的参数辨识方法的有效性,建立了相应的实验装置并对模型进行了实验验证。研究结果表明,Bouc-Wen模型的最大绝对误差为3.78μm,最大相对误差为5.79%,表明Bouc-Wen模型及相应的参数辨识方法能较好地模拟WTYD型压电陶瓷微位移器的迟滞特性。     

MRD模型参数识别及其在振动控制中的应用

为了识别磁流变阻尼器(MRD)Bouc-Wen模型中的未知参数,提高半主动控制中的参数通用性,提出一种逐渐缩小参数取值范围的遗传算法(GA)提高识别精度,并根据参数随电流的变化趋势对其函数关系进行拟合。对MRD Bouc-Wen模型进行了数值仿真设计。除试验数据外,在无其他先验知识的条件下利用遗传算法进行了参数识别,并在建立62个自由度铁道车辆整车模型的基础上进行了悬挂半主动控制系统数值仿真分析,用于验证识别出的Bouc-Wen模型。仿真结果表明,利用遗传算法识别的MRD Bouc-Wen模型进行半主动控制可以有效降低车体横向加速度,提高车辆运行平稳性能。     

压电执行器的Bouc-Wen模型在线参数辨识

现有的定参数Bouc-Wen模型由于无法表征压电执行器迟滞具有的频移和时变性,极易产生较大的模拟误差。为了精确地模拟压电执行器的迟滞特性,本文建立了压电执行器的Bouc-Wen模型,并采用递推最小二乘在线辨识方法来实时辨识Bouc-Wen模型的参数。为了避免出现数据饱和现象,使用限定记忆来限定辨识方法所使用的数据组数。为验证该辨识方法的有效性,建立了相应的实验系统对其进行实验验证。实验结果表明,限定记忆递推最小二乘在线辨识方法能使Bouc-Wen模型也呈现频移和时变特性。以100 Hz的驱动电压为例,其最大绝对模拟误差从1.38μm降为0.51μm。因此,与传统的离线参数辨识方法相比,限定记忆递推最小二乘在线辨识方法能够有效地提高Bouc-Wen模型的模拟精度。     

Three-stage Method for Identifying the Dynamic Model Parameters of Stranded Wire Helical Springs

The dynamic behavior of the stranded wire helical spring is described by a modified Bouc-Wen model while the model parameters must be identified using an identification method and experimental data. Existing identification methods usually relies either solely nonlinear iterative algorithms or manually trial and error. Therefore, the identification process can be rather time consuming and effort taking. As a result, these methods are not ideal for engineering applications. To come up with a more practical method, a three-stage identification method is proposed. Periodic loading and identification simulations are carried out to verify the effectiveness of the proposed method. Noises are added to the simulated data to test the performance of the proposed method when dealing with noise contaminated data. The simulation results indicate that the proposed method is able to give satisfying results when the noise levels are set to be 0.01, 0.03, 0.05 and 0.07. In addition, the proposed method is also applied to experimental data and compared with an existing method. The experimental data is acquired through a periodic loading test. The experiment results suggest that the proposed method features better accuracy compared with the existing method. An effective approach is proposed for identifying the model parameters of the stranded wire helical spring.     

WTYD型压电陶瓷微位移器的迟滞特性模拟

为了模拟WTYD型压电陶瓷微位移器的输出位移与驱动电压之间的迟滞曲线,本文通过采用Bouc-Wen模型模拟迟滞分量提出了一种表征WTYD型压电陶瓷微位移器的输出位移与驱动电压之间的迟滞关系的Bouc-Wen模型并建立了相应的参数辨识方法。为了验证Bouc-Wen模型及其相应的参数辨识方法的有效性,建立了相应的实验装置并对模型进行了实验验证。研究结果表明,本文提出并研究的WTYD型压电陶瓷微位移器的Bouc-Wen模型及相应的参数辨识方法能较好地模拟WTYD型压电陶瓷微位移器的迟滞特性。     

A velocity based active vibration control of hysteretic systems

Hysteresis is a property of systems that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state. A velocity based active vibration control, along with a special class of hysteretic models using passive functions are presented in this paper. This hysteretic model is based on a modification of the Bouc-Wen model, where a nonlinear term is replaced by a passive function. The proposed class retains the rate-independence property of the original Bouc-Wen model, and it is able to reproduce several kinds of hysteretic loops that cannot be reproduced with the original Bouc-Wen model. Using this class of hysteretic models, a chattering velocity-based active vibration control scheme is developed to mitigate seismic perturbations on hysteretic base-isolated structures. Our hysteretic model is used because of its simplicity in proving the stability of the closed-loop system; i.e., a controller is designed using the proposed model, and its performance is tested on the original hysteretic system, modeled with Bouc-Wen. Numerical experiments show the robustness and efficiency of the proposed control algorithm.     

栓接结合部在动载荷下的能量耗散特性

研究栓接结合部在动载荷下的能量耗散特性,对描述机械系统复杂力学行为具有重要的理论和实际意义。利用Bouc-Wen模型模拟栓接结合部的迟滞非线性特性,提出在动载荷下系统能量耗散计算方法和参数辨识方法。为验证所提方法的正确性,利用Mindlin模型所仿真出的非线性迟滞曲线作为栓接结合部所获得的试验数据,对Bouc-Wen模型进行参数辨识,并采用力控制方式分析Bouc-Wen模型中各个参数对系统能量耗散特性的影响规律。结果表明:随着量纲一切向力的增加量纲一能量耗散随之非线性递增;参数A、δ、γ和n对能量耗散的影响与其灵敏度相关,灵敏度越大则能量耗散的递增速率也越大;能量耗散随着参数A、γ和n的增加而增加,但参数δ则反之;栓接结合部能量耗散不仅与Bouc-Wen模型中的参数相关,而且与系统激励频率和振幅非线性相关;量纲一切向力与量纲一能量耗散之间关系可表示为η=aΓb的函数形式。     

Genetic algorithm with an improved fitness function for (N)ARX modelling

In this article a new fitness function is introduced in an attempt to improve the quality of the auto-regressive with exogenous inputs (ARX) model using a genetic algorithm (GA). The GA is employed to identify the coefficients and the number of time lags of the models of dynamic systems with the new fitness function which is based on the prediction error and the correlation functions between the prediction error and the input and output signals. The new fitness function provides the GA with a better performance in the evolution process. Two examples of the ARX modelling of a linear and a non-linear (NARX) simulated dynamic system are examined using the proposed fitness function.     

基于改进遗传算法的最小二乘法的应用

为了克服基本遗传算法参数较多时编码表示冗长、烦杂以及实数编码等寻优效果的不足,提出了一种改进编码的遗传算法——矩阵编码遗传算法.它是在遗传算法大的框架不变的情况下仅改变其编码,即遗传编码改变的同时,相应的遗传操作,包括交叉、变异等都要随之变化.除此之外,适应度函数和计算也要变化.最小二乘法是系统辨识常用方法之一,将改进...     

Adaptive infinite impulse response system identification using modified-interior search algorithm with Lèvy flight

In this paper, a new meta-heuristic optimization technique, called interior search algorithm (ISA) with Lèvy flight is proposed and applied to determine the optimal parameters of an unknown infinite impulse response (IIR) system for the system identification problem. ISA is based on aesthetics, which is commonly used in interior design and decoration processes. In ISA, composition phase and mirror phase are applied for addressing the nonlinear and multimodal system identification problems. System identification using modified-ISA (M-ISA) based method involves faster convergence, single parameter tuning and does not require derivative information because it uses a stochastic random search using the concepts of Lèvy flight. A proper tuning of control parameter has been performed in order to achieve a balance between intensification and diversification phases. In order to evaluate the performance of the proposed method, mean square error (MSE), computation time and percentage improvement are considered as the performance measure. To validate the performance of M-ISA based method, simulations has been carried out for three benchmarked IIR systems using same order and reduced order system. Genetic algorithm (GA), particle swarm optimization (PSO), cat swarm optimization (CSO), cuckoo search algorithm (CSA), differential evolution using wavelet mutation (DEWM), firefly algorithm (FFA), craziness based particle swarm optimization (CRPSO), harmony search (HS) algorithm, opposition based harmony search (OHS) algorithm, hybrid particle swarm optimization-gravitational search algorithm (HPSO-GSA) and ISA are also used to model the same examples and simulation results are compared. Obtained results confirm the efficiency of the proposed method.     

用遗传算法识别转子-轴承系统中的支承刚度

提出用基因算法识别转子—轴承系统有限元模型中支承刚度的新方法，给出基因算法识别支承刚度的步骤，并通过算例讨论人口数与突变概率对收敛速度与计算时间的影响。研究结果表明，这种方法是基于自然界优胜劣汰规律的随机迭代搜索，不仅可以避免优化过程对待识别参数初值的依赖，而且可以有效地解决优化迭代过程不能用解析式表示的复杂问题。     

Using the modified PSO method to identify a Scott-Russell mechanism actuated by a piezoelectric element

This paper mainly proposes an efficient modified particle swarm optimization (MPSO) method, to identify a Scott-Russell (SR) magnification mechanism driven by a piezoelectric actuator (PA), in which Bouc-Wen model is employed to describe the hysteresis phenomenon. In system identification, we adopt the MPSO to find parameters of the SR mechanism and the PA. This new algorithm is added with “distance” term in the traditional PSO's fitness function to avoid converging to a local optimum. It is found that the MPSO method can obtain optimal high-quality solution, high calculation efficiency, and its feasibility and effectiveness are demonstrated for the modified IEEE 30-bus system. Finally, the comparisons of numerical simulations and experimental results prove that the MPSO identification method for the SR magnification mechanism is feasible.     

Alternative method for identification of the dynamic properties of bolted joints

Bolted joints often have a significant effect on the dynamical behavior of assembled mechanical structures. An accurate model of an assembled structure depends on correctly determining and identifying the dynamic parameters of bolted joints. This paper presents an alternative method for identifying these dynamic parameters using structure??s natural frequency and damping. A novel experiment is designed with a test piece consisting of only bolted joints, with the governing equations of the test piece established using the analytical method. The relationships between the equivalent dynamic parameters of the bolted joints and the natural frequencies and damping ratios of the test piece are determined for both the normal and tangential directions. The parameter identification problem for bolted joints is thus transformed into a test of the natural frequency and the damping ratio of the test piece. In order to check the accuracy of the proposed identification method, the test piece and bolted joints are modeled using the finite element method (FEM) and the dynamic properties of the test piece are analyzed. The maximum error between the natural frequencies of the FEM result and the experimental values in the normal and tangential models are 4.73% and 0.34%, respectively. The result indicates that the proposed method is valid for the dynamic parameter identification of bolted joints.     

基于自适应遗传算法的虚拟企业伙伴选择求解

针对虚拟企业合作伙伴的选择问题,根据虚拟企业的市场目标,采用层次分析算法确定评价因子的权重,然后建立多目标的虚拟企业伙伴选择优化模型.为简化模型,以最短的完工时间、最低的成本和最高的信誉度为目标.在遗传过程中对各个单目标进行排序选择,通过对交叉、变异算子进行自适应改进,采用最优保存策略迭代求出最佳合作伙伴及分配的具体工作量.通过与普通遗传算法的对比,仿真算例验证了改进后的算法的优越性.     

A hybrid model using supporting vector machine and multi-objective genetic algorithm for processing parameters optimization in micro-EDM

In micro-electrical discharge machining (EDM), processing parameters greatly affect processing efficiency and stability. However, the complexity of micro-EDM makes it difficult to determine optimal parameters for good processing performance. The important output objectives are processing time (PT) and electrode wear (EW). Since these parameters influence the output objectives in quite an opposite way, it is not easy to find an optimized combination of these processing parameters which make both PT and EW minimum. To solve this problem, supporting vector machine is adopted to establish a micro-EDM process model based on the orthogonal test. A new multi-objective optimization genetic algorithm (GA) based on the idea of non-dominated sorting is proposed to optimize the processing parameters. Experimental results demonstrate that the proposed multi-objective GA method is precise and effective in obtaining Pareto-optimal solutions of parameter settings. The optimized parameter combinations can greatly reduce PT while making EW relatively small. Therefore, the proposed method is suitable for parameter optimization of micro-EDM and can also enhance the efficiency and stability of the process.     

基于遗传算法的ARMA模型定阶新技术

针对时间序列分析与预测中最为常见的ARMA模型的定阶问题,在分析传统定阶方法缺点的基础上,提出了用遗传算法确定ARMA(n,m)模型的自回归阶数n和滑动平均阶数m的新方法。首先由ARMA模型的预测值与实测值定义平均相对变动值(Average relative variance,ARV),并根据其建立遗传算法的适应度函数;然后选取适当的种群数、交叉效、变异率及进化代数;通过逐代进化,得到最优的ARMA模型。最后,通过太阳黑子数据验证了基于遗传算法的ARMA模型定阶新技术的有效性和实用性。     

压电陶瓷作动器非对称迟滞建模与内模控制

压电陶瓷作动器被广泛应用于精密定位和控制中,但其本身存在的非对称迟滞非线性特性,严重影响了系统的定位和控制精度。针对这一问题,提出了一种基于广义Bouc-Wen模型的非对称迟滞建模方法,并利用差分进化算法辨识模型参数;基于所建的广义Bouc-Wen模型构建了其具有解析形式的迟滞逆模型,并设计了内模控制方案实现对压电陶瓷作动器的精密跟踪控制;最后在压电陶瓷作动器实验平台,对所提出的建模和控制方案进行了实验验证。对压电陶瓷作动器的建模结果表明,系统建模误差均小于0.051 0,比经典Bouc-Wen模型的建模误差降低约21%～46%;对100 Hz内幅值为20μm的期望位移信号的控制实验结果表明,所提出的控制方法具有良好的实时跟踪性能和跟踪控制精度。对100 Hz期望信号的跟踪控制均方根误差为0.491 6μm,相对误差为0.040 2μm,可以很好地满足实际工程需要。     

叠堆式压电陶瓷驱动器的复合控制

提出了逆Bouc-Wen前馈控制与反馈控制相结合的复合控制算法,用于改善压电陶瓷驱动器对目标轨迹的跟踪性能。建立了压电陶瓷驱动器的Bouc-Wen迟滞动力学模型,并用粒子群算法(PSO)对该模型的参数进行识别。基于Bouc-Wen迟滞模型,提出了逆Bouc-Wen前馈补偿控制。最后,为消除迟滞模型的不确定性,引入比例积分(PI)反馈控制,并与前馈补偿控制构成复合控制算法。建立了基于dSPACE实时系统的压电陶瓷驱动实验平台,迟滞实验结果表明:压电陶瓷的迟滞误差量几乎为0,线性度高达96.5%;目标轨迹跟踪实验结果表明:复合控制算法的最大跟踪误差为0.180 5μm,均方根(RMS-Root mean square)跟踪误差为0.055 4μm,跟踪精度达到了10-8 m。相比于开环控制、前馈控制及PI反馈控制,提出的复合控制算法能够基本消除压电陶瓷的迟滞非线性,同时具有很好的轨迹跟踪性能。     

RESEARCH ON THE MINIMUM ZONE CYLINDRICITY EVALUATION BASED ON GENETIC ALGORITHMS

A genetic algorithm (GA)-based method is proposed to solve the nonlinear optimization problem of minimum zone cylindricity evaluation. First, the background of the problem is introduced. Then the mathematical model and the fitness function are derived from the mathematical definition of dimensioning and tolerancing principles. Thirdly with the least squares solution as the initial values, the whole implementation process of the algorithm is realized in which some key techniques, for example, variables representing, population initializing and such basic operations as selection, crossover and mutation, are discussed in detail. Finally, examples are quoted to verify the proposed algorithm. The computation results indicate that the GA-based optimization method performs well on cylindricity evaluation. The outstanding advantages conclude high accuracy, high efficiency and capabilities of solving complicated nonlinear and large space problems.     

Modeling of binocular vision system for 3D reconstruction with improved genetic algorithms

This paper models the binocular vision system focused on 3D reconstruction and describes an improved genetic algorithm (GA) for estimating camera system parameters. The two-camera system model that takes into account camera radial distortion includes a total of 24 parameters. The proposed improved GA is used to solve this nonlinear optimization problem with high dimension. In our improved GA, the adaptive control of camera parameter search interval and the catastrophe strategy with elitist preservation are employed. The experimental results indicate that our improved GA is effective to solve the multi-peak function optimization problem and the 3D reconstruction accuracy of the binocular vision system is promising.