基于形状记忆合金驱动器的微纳定位系统鲁棒自适应控制

针对基于智能材料驱动器串联驱动的微纳定位系统,本文主要探讨了此类高精定位系统的控制设计策略.其控制设计的主要任务是消除驱动器中未知回滞特性对系统性能所造成的负面影响.本文重点以形状记忆合金驱动器为例,采用基于广义play算子的广义Prandtl-Ishlinskii回滞模型来表征形状记忆合金驱动器中的未知饱和回滞非线性,并在此基础上提出了一种鲁棒自适应控制设计方法来消除前置回滞存在的影响.设计的控制器在保证全局稳定性的基础上能实现理想的跟踪精度,仿真结果验证了控制策略的有效性和正确性.     

基于Prandtl-Ishlinskii模型的一类回滞非线性系统自适应控制

对带回滞驱动的一类单输入单输出的非线性不确定系统,本文采用Prandtl-Ishlinskii模型描述回滞特性,采用反步递推设计方法,实现自适应控制器的设计.仿真结果说明控制方法的有效性.     

类反斜线回滞系统的模型参考滑模控制

回滞现象广泛地存在于许多控制研究领域,可能引起系统的振荡,甚至造成系统的不稳定,因此有必要对回滞系统的有效控制进行研究.针对一类重要的类反斜线回滞系统,通过对类反斜线回滞特性的分析,将其分解为线性部分和已知上限的非线性不确定部分,给定期望的不存在回滞特性的光滑轨线,得到了模型参考滑模控制律,通过跟踪给定期望的不存在回滞特性的光滑轨线,削弱甚至消除回滞特性.仿真结果表明此控制律是有效的.     

基于输出反馈的欠驱动TORA系统的有界输入控制

针对欠驱动TORA(Translational oscillations with a rotational actuator)系统,设计了一种具有执行器饱和约束的输出反馈等[7]特别地,由Rand学者提出的TORA系统,最初控制器.与其他现有方法相比,本文方法不仅考虑了执行器饱和约束和作为双自旋航天器的简化模型用于研究自振现象.后来由于速度信号不可测情形,而且考虑了旋转小球可能存在的循环行为.具体而TORA系统具有强耦合、高度非线性、欠驱动等特性,而被言,首先根据TORA系统模型分析了TORA系统的控制目标;随后,作为一种非线性基准系统主要用于非线性控制器设计、验证构造了一种新颖的能量函数,在此基础上设计了一种考虑执行器饱和约非线性控制算法的控制性能或教学研究.目前国内外已有多束的输出反馈控制器,并通过严格的数学分析证明了闭环系统关于平衡点的稳定性;最后,借助数值仿真测试检验了所提控制器的控制性能,并所高校和研究机构针对TORA系统的控制问题展开研究.对与已有方法进行了对比.仿真测试结果表明本文所提方法具有更好的控法制性能.     

双侧电驱动履带车辆运动解耦与变结构控制

针对双侧电驱动履带车辆运动控制强非线性、强耦合和不确定性的特点,提出一种解耦的控制结构,并设计各子系统控制器.首先,将运动控制系统分解为速度、横摆角速度两个独立子系统,克服传统差速控制存在的强耦合.其次,采用积分滑模控制方法,引入非线性积分滑模面,设计了能有效克服路面不确定扰动、消除积分饱和的速度控制器,实现车速的无超调、无静差的跟踪;考虑驱动电机饱和约束,结合模糊自适应与滑模控制算法,设计了能够适应转向阻力非线性变化的横摆角速度控制器,提高车辆转向运动控制的抗扰能力、降低控制量抖振.仿真结果表明,控制策略实现多种工况下车辆快速、准确的直线、转向运动控制.     

连续回滞系统的模型参考自适应控制

采用Stop和Play算子表示的Prandtl-Ishlinskii回滞模型描述回滞特性，该模型便于实现控制器的设计．考虑带有未知回滞驱动且以状态空间形式表示的连续时间线性动态系统，给出了模型参考白适应控制设计方案．控制策略保证闭环系统的全局稳定性和期望的跟踪精度，有效地抑制回滞产生的不精确和振荡现象．数值仿真结果表明了控制算法的有效性．     

环形弹簧阻尼器的滞回性能试验研究

环形弹簧是一种在机械工程领域中应用广泛的减振部件.将环形弹簧用于土木工程结构的减震控制,设计了一种具有自复位功能的环形弹簧阻尼器(Ring spring damper,RD),通过往复荷载作用下的性能试验,研究了RD的滞回性能.首先,提出RD的构造设计和工作原理.进而,设计加工了RD试件,对其进行了滞回性能试验,研究了位移幅值、加载频率对RD试件滞回特性的影响规律.最后,利用ABAQUS软件,对RD试件的滞回性能进行了数值模拟.研究结果表明,RD在往复荷载作用下的滞回性能稳定,且具有良好的耗能与复位特性；RD的有限元模拟滞回曲线与试验曲线较为接近,表明所建立的有限元模型可较为准确地描述RD的滞回行为.     

一类输入饱和非仿射非线性系统的非线性动态逆控制

输入饱和是实际系统中经常遇到的问题,很多已有的控制方法要求被控系统具有仿射结构.本文针对一类具有输入饱和的非仿射纯反馈非线性系统提出了一种基于奇异值摄动理论的非线性动态逆控制方法.首先构建一个快变子系统,在慢时间尺度下将非仿射非线性系统转换为具有仿射结构的线性系统,从而应用已有的控制算法实现控制目的.为了消除输入饱和带来的影响,建立一个中间子系统对理想控制量与输入饱和限制下控制量的差进行估计和补偿.所提出的控制方法不依赖于被控系统固有的时标分离特性,并能证明闭环系统指数跟踪参考轨迹.该方法具有良好的扩展性,可以根据实际需求与多种控制算法相结合.与动态面控制器和传统近似动态逆控制器的对比仿真结果验证了本文控制方法的有效性.     

输出死区下的随机多智能体系统一致性饱和控制

针对一类存在输入饱和和输出死区现象的非严格反馈非线性随机多智能体系统,提出一种自适应神经网络一致性饱和控制算法.首先,为了解决非对称输入饱和问题,构造一类与所考虑智能体相同阶次的辅助系统;然后,以反步法和辅助系统作为框架,利用神经网络处理系统中的未知非线性函数,并结合Nussbaum函数解决输出死区问题;接着,利用动态面控制技术避免“计算爆炸”问题;然后,基于李雅普诺夫稳定性理论验证所提出的控制算法能够保证闭环系统全部信号依概率半全局一致最终有界;最后,通过数值仿真和实例仿真的结果验证所提出控制算法的有效性.     

一类非线性随机系统的在线优化算法

讨论一类随机非线性系统的在线优化问题,系统中的非线性函数可以是未知的.在基于性能势的优化方程框架下,通过系统样本路径设计性能势函数的在线学习算法,进一步给出优化控制算法.在此基础上利用RBF神经网络的逼近特性,给出简化学习算法以减少计算量.最后给出的具体仿真结果和数据表明本文算法的有效性.     

Adaptive control of system involving complex hysteretic nonlinearities: a generalised Prandtl–Ishlinskii modelling approach

In this article an adaptive control approach is proposed for a class of nonlinear systems preceded by unknown hysteretic nonlinearities, which is described by a generalised Prandtl–Ishlinskii (P-I) model. The main feature is that the generalised P-I hysteresis model is counted in the controller design without constructing a hysteresis inverse. The developed controller guarantees the global stability of the system and tracking a desired trajectory to a certain precision is achieved. The effectiveness of the proposed control approach is demonstrated through simulation example.     

Adaptive Pseudo Inverse Control for a Class of Nonlinear Asymmetric and Saturated Nonlinear Hysteretic Systems

This paper aims at eliminating the asymmetric and saturated hysteresis nonlinearities by designing hysteresis pseudo inverse compensator and robust adaptive dynamic surface control (DSC) scheme. The “pseudo inverse” means that an on-line calculation mechanism of approximate control signal is developed by applying a searching method to the designed temporary control signal where the true control signal is included. The main contributions are summarized as: 1) to our best knowledge, it is the first time to compensate the asymmetric and saturated hysteresis by using hysteresis pseudo inverse compensator because the construction of the true saturated-type hysteresis inverse model is very difficult; 2) by designing the saturated-type hysteresis pseudo inverse compensator, the construction of true explicit hysteresis inverse and the identifications of its corresponding unknown parameters are not required when dealing with the saturated-type hysteresis; 3) by combining DSC technique with the tracking error transformed function, the “explosion of complexity” problem in backstepping method is overcome and the prespecified tracking performance is achieved. Analysis of stability and experimental results on the hardware-in-loop platform illustrate the effectiveness of the proposed adaptive pseudo inverse control scheme.      

具有Preisach类型磁滞输入的不确定非线性系统 自适应神经网络控制

本文针对一类执行器受Preisach磁滞约束的不确定非线性系统, 提出一种基于神经网络的直接自适应控制 方案, 旨在解决系统的预定精度轨迹跟踪问题. 由于Preisach算子与系统动态发生耦合, 导致算子输出信号不可测 量, 给磁滞的逆补偿造成了困难. 为解决此问题, 本文首先将Preisach模型进行分解, 以提取出控制命令信号用于 Backstepping递归设计, 并在此基础上融合一类降阶光滑函数与直接自适应神经网络控制策略, 形成对磁滞非线性 和被控对象非线性的强鲁棒性能, 且所设计方案仅包含一个需要在线更新的自适应参数, 同时可保证Lyapunov函数 时间导数的半负定性. 通过严格数学分析, 已证明该方案不仅保证闭环系统所有信号均有界, 而且输出跟踪误差随 时间渐近收敛到用户预定区间. 基于压电定位平台的半物理仿真实验进一步验证了所提出控制方案的有效性.     

形状记忆合金驱动器的自适应滑模反步控制

形状记忆合金(SMA)作为一种智能材料,相对于传统的驱动器具有功率重量比大、驱动电压低、质量轻、干净、无噪音等特性,被广泛应用在各领域.然而,非线性、迟滞、时变等因素影响了形状记忆合金的控制精度,限制了它的应用.为此,本文提出了自适应滑模反步控制方法,用于解决精确控制问题.文中首先搭建了实验装置,建立了形状记忆合金的机理模型;然后,采用最小二乘算法辨识了模型参数;最后,基于机理模型设计了自适应滑模反步控制器.实验结果表明,本文提出的方法具有动态响应快、跟踪精度高和抗干扰能力强的特性.     

Adaptive backstepping control of a class of uncertain nonlinear systems with unknown backlash-like hysteresis

In this note, we consider the same class of systems as in a previous paper, i.e., a class of uncertain dynamic nonlinear systems preceded by unknown backlash-like hysteresis nonlinearities, where the hysteresis is modeled by a differential equation, in the presence of bounded external disturbances. By using backstepping technique, robust adaptive backstepping control algorithms are developed. Unlike some existing control schemes for systems with hysteresis, the developed backstepping controllers do not require the uncertain parameters within known intervals. Also, no knowledge is assumed on the bound of the "disturbance-like" term, a combination of the external disturbances and a term separated from the hysteresis model. It is shown that the proposed controllers not only can guarantee global stability, but also transient performance.     

Modeling and time delay control of shape memory alloy actuators

Shape memory alloy (SMA) actuators possess hard nonlinearities including backlash-like hysteresis and saturation. These nonlinearities result in steady-state error and limit-cycle problems when conventional controllers such as the proportional integral derivative (PID) are used for trajectory control. In this study, a dynamics for an SMA actuator was newly derived using the modified Liang's model. The derived dynamics showed continuity at the change of the phase transformation process, but the original model could not. SMA actuator characteristics could be well described using this dynamics. The derived dynamics could be also used effectively for the prediction of control performance and gain tuning of the time delay control (TDC). The dynamics consisted of first-order linear and second-order nonlinear equations. Accordingly, a control strategy was established for the TDC to regulate only the second-order nonlinear part for simplicity and for the internal closed loop to regulate the rest. The control strategy was examined from the point of view of influence of an antiwindup scheme and high gain tuning on control performance. An anti-windup scheme was essential to protect windup phenomenon and high gain tuning was effective when a temperature disturbance existed. In the robustness test, the TDC with high gains showed robustness to inertia variation and temperature disturbance in comparison with the TDC with low gains.     

压电舵机动态迟滞建模与带有鲁棒干扰观测器的两自由度控制

压电宏纤维复合材料(MFC)驱动的舵机具有功耗低、质量小以及可靠性高等优点,在无人飞行器领域有很大的应用潜力.压电材料的动态迟滞非线性会降低舵机的控制精度和稳定性, MFC柔性结构使舵机易受外扰影响.本文首先建立MFC舵机Hammerstein动态迟滞非线性模型,并设计了迟滞逆补偿器.针对模型不确定性和外扰影响,设计了带有鲁棒干扰观测器的二自由度控制器,保证在外扰和模型不确定性下控制系统的鲁棒性. MFC舵机控制实验结果表明,所设计的控制器具有良好的抗干扰性能和鲁棒性,较传统干扰观测器显著提高了控制性能.     

Thin film shape memory alloy microactuators

Thin film shape memory alloys (SMAs) have the potential to become a primary actuating mechanism for mechanical devices with dimensions in the micron-to-millimeter range requiring large forces over long displacements. The work output per volume of thin film SMA microactuators exceeds that of other microactuation mechanisms such as electrostatic, magnetic, thermal bimorph, piezoelectric, and thermopneumatic, and it is possible to achieve cycling frequencies on the order of 100 Hz due to the rapid heat transfer rates associated with thin film devices. In this paper, a quantitative comparison of several microactuation schemes is made, techniques for depositing and characterizing Ni-Ti-based shape memory films are evaluated, and micromachining and design issues for SMA microactuators are discussed. The substrate curvature method is used to investigate the thermo-mechanical properties of Ni-Ti-Cu SMA films, revealing recoverable stresses up to 510 MPa, transformation temperatures above 32°C, and hysteresis widths between 5 and 13°C. Fatigue data shows that for small strains, applied loads up to 350 MPa can be sustained for thousands of cycles. Two micromachined shape memory-actuated devices-a microgripper and microvalve-also are presented     

A new method for actuating parallel manipulators

This paper presents a new technique of actuating a parallel platform manipulator using shape memory alloy (SMA). This is a type of smart materials that can attain a high strength-to-weight ratio, which makes them ideal for miniature application. The work is mainly to develop a new SMA actuator and then incorporating the actuator in building the parallel manipulator prototype. The SMA used in this study is a commercial NiTi wire. The SMA wire provides an actuating force that produces a large bending and end displacement. A 3-UPU (universal–prismatic–universal) parallel manipulator using linear SMA actuators was developed. The manipulator consists of a fixed platform, a moving platform and three SMA actuators. The manipulator workspace was specified based on the restrictions due to actuator strokes and joint angle limits. System identification techniques were used to model both heating and cooling processes. An ON/OFF control was performed and the results showed closeness in simulation and experimental results. This study showed that shape memory alloy actuated beam can successfully be used to provide linear displacement. The built prototype indicates the feasibility of using SMA actuators in parallel manipulators.     

Modeling of single and multilayer polyvinylidene fluoride film for micro pump actuation

Micro pumps are essential components of micro devices such as drug delivery systems. Large numbers of pumps have been proposed based on different actuating principles. Piezoelectric actuation offers advantages such as reliability and energy efficiency. Lead zirconate titanate (PZT) based piezoelectric actuation for micro pumps is predominantly explored despite its disadvantages such as brittle nature, low straining and difficulties in processing. Polymer piezoelectric materials like polyvinylidene fluoride (PVDF) could be promising replacements for PZT owing to their availability in form of films and good strain coefficients. Very limited literature on micro pump with PVDF as an actuator is available. In this paper, finite element analysis (FEA) model of a micro pump actuator using single and multilayer PVDF for actuation is developed in ANSYS^?. The model takes into account the influence of driving voltage and actuator geometry. The central deflection of the pump diaphragm which is instrumental in defining the pump performance is studied for driving voltages of 100?C200?V. The deflection of the pump diaphragm for single layer and multilayer actuation are determined from the model. It could be inferred from the initial part of the study that pump performance depends on driving voltage and actuator film thickness. In order to reduce driving voltage requirement multilayer stacked actuator is tried with four different configurations of the layers. It is concluded that stacking configuration of parallel energized straight polarity PVDF layers yielded best central deflection. An attempt is made to compare the performance of multilayer actuator with an equivalent single thick layer actuator. It is noticed that the multilayer actuator performance was better by about 101% when number of layers is doubled.