主动桁架的控制策略的研究

于桁架结构中集成若干传感器、作动器及控制器,构成主动桁架;针对这一主动桁架,采用传感器和作动器同位配置,分别设计了负速度反馈、LQG和H∞这3种控制器。仿真结果表明,采用速度反馈控制律时,从其极点分布可以看出,同位配置系统零-极点相间排列,当控制作用施加于结构时,结构的阻尼增加,零-极点向复平面的左半平面移动,系统具有鲁棒稳定性;与速度反馈、LQG控制器比较,H∞控制器方法不但可以增加被空模态的阻尼,而且在控制带宽范围以外,使得系统对溢出问题具有鲁棒性。     

配置压电传感器/驱动器的柔性结构振动主动控制研究

研究压电传感器/驱动器同位布置情况下柔性悬臂梁的振动主动控制问题,建立模态坐标为变量的状态方程,分别采用LQG(linear quadratic gauss)控制和鲁棒H∞控制技术设计振动主动控制系统。仿真结果表明,文中给出的控制方法是有效的,能有效抑制悬臂梁的振动,与LQG控制设计方法相比,鲁棒H∞控制对模态参数摄动具有较强的鲁棒性以及较好的闭环动态性能,能保证系统在不确定性因素作用的情况下,具有良好的振动抑制效果。     

以压电陶瓷为作动器的主动隔振研究

本文讨论了压电陶瓷作动器的性能和基于共振情况下的柔性结构的高频窄带主动隔振技术。由压电陶瓷作为作动器，激振器作为干扰源，铝制悬臂梁作为结构组成了系统装置。由力传感器将结构的信号经补偿器补偿后作用于作动器组成了闭环主动隔振系统，最后给出了经典的二阶补偿下的闭环隔振实验结果。     

基于平面五杆闭环结构的空间并联机构类型综合与拓扑分析

分析了五杆闭环结构的类型、拓扑描述、组成形式和运动性能 ,重点研究了基于 5R闭环结构与RPRPR闭环结构在空间并联机构中的应用 ,给出了基于五杆闭环结构的空间并联机构的类型综合方法及步骤 ,并综合出了九种空间并联机构的构型。     

并联机构闭环四杆结构研究

研究闭环结构的分类和拓扑描述,闭环四杆结构的组成形式、运动性能及闭环四杆结构在平面并联机构和空间并联机构中的用法,提出了在不同形式下的闭环结构的拓扑描述,为并联机构型数综合及并联机构构型的创新设计提供有效的方法。     

基于人机适应的下肢康复训练器人机建模与受力分析

从下肢康复患者的需要和节约成本出发,设计了一种人机融合性好、机械结构简单,具备功能性电刺激接口的脚踏车式下肢康复训练器。该训练系统能针对不同损伤程度的下肢残障者提供被动、主动、抗阻3种康复训练模式。根据人机适应(human adaptive mechatronics,HAM)概念中在约束环境下对人机建模的思路进行动力学研究,在结合人体下肢运动机理的基础上提出了一种平面闭环铰链五连杆刚体模型,介绍了康复设备的结构,对主动踏车运转过程中踝关节的运动进行了分析和优化,基于平面闭环铰链五连杆分析了抗阻训练时人机系统的静力学,建立了数学模型。根据人体下肢模型建立了虚拟样机,并进行了动力学仿真,验证了前述分析的正确性。     

新型同位阻尼磁轴承模型及其特性研究

针对以往磁轴承转子系统的振动抑制能力不足的问题,对新型同位电磁阻尼和单自由度磁轴承转子系统进行了研究,提出了一种同位电磁阻尼并应用到抑制磁悬浮转子的振动中。基于以往阻尼力模型重新推导了同位阻尼力数学模型,考虑了线圈电流变化对阻尼力模型的影响,并利用磁矢位计算使阻尼力模型更加精准,分析了同位阻尼力在转子上的分布情况及与电流和位移的关系。将同位阻尼与单自由度磁轴承相结合,建立了新型同位阻尼磁轴承模型,利用该磁轴承模型对同位阻尼抑制转子振动能力进行了分析。仿真结果表明,新型磁轴承模型中的同位阻尼能够将转子最大振动位移偏差从无阻尼时的1.65×10-5m减小到2×10-6m,明显地减小了转子系统的位移偏差,能够达到增强磁轴承转子系统抑制振动能力的目的。     

并联机构环四杆结构研究

研究闭环结构的分类和拓扑描述，闭环四杆结构的组成形式、运动性能及闭环四杆结构在平面并联机构和空间并联机构中的用法，提出了在不同形式下的闭环结构的拓扑描述，为并联机构型数综合及并联机构构型的创新设计提供有效的方法。     

电主轴单元热误差半闭环主动控制方法

作为影响数控机床精度稳定性的关键因素,电主轴末端热误差不仅由主轴轴承、电机生成热量引起,更与加工环境温度不稳定性密切相关.为在机床加工状态下并行抑制上述热干扰因素以保证主轴精度稳定性,构建了一种面向电主轴单元热误差的半闭环主动控制方法,该方法基于模糊神经网络-PID主动控制策略对电主轴单元内置循环液供液温度进行动态调整,以实现电主轴单元结构温度稳定性控制与热误差半闭环主动抑制.通过试验证明:该方法可以在22℃～18℃温度缓降工作环境中,将电主轴单元结构温升幅度控制在±0.5℃以内;并且相比于传统循环冷却控制方法,该方法可有效抑制各项主轴热误差(降低比例δx为57.1％,δy为56.9％,δz为34.7％),并放宽了电主轴单元精度稳定性维持对恒温加工环境的要求.     

柔性转子振动主动控制研究现状

对柔性转子系统动力学研究进行了回顾,综述了柔性转子主动振动闭环控制系统中作动器、控制器控制律设计研究的现状与进展,对柔性转子主动振动控制技术的发展趋势进行了展望。     

Effect of modal filter errors on vibration control characteristics

When designing a control system for vibration suppression of flexible structures using modal control strategy, one must know the modal displacements and velocities of the controlled modes. If the vibration control forces are designed based on inaccurate modal states, the closed-loop performance of the vibration control system will be degraded depending on the extent of the modal filter errors. In this study, the effect of modal filter errors on the vibration control characteristics of flexible structures is analyzed for IMSC (Independent Modal Space Control). A Lyapunov asymptotic stability condition that depends on the magnitude of the modal filter errors is derived. The extent of the response deviation of the closed-loop system is also derived and evaluated using operator techniques. The extent of the response deviation is found to be proportional to the magnitude of the modal filter errors.     

综合模态H2范数下致动器/传感器的优化配置

致动器/传感器的优化配置问题是智能柔性结构振动主动控制中的关键技术问题,基于模态空间H_2范数研究了智能柔性梁系统中压电致动器/传感器的优化配置问题。根据Rayleigh-Ritz理论建立了系统的动力学方程并得到其状态空间表达式。提出了一种衡量系统能控/能观性并考虑模态权重的综合模态H_2范数准则,采用改进遗传算法研究系统中并置致动器/传感器的优化配置问题,得到了系统多个模态、综合模态H_2范数最优的致动器/传感器布局结果。实验结果表明,利用优化结果进行致动器/传感器的布局,系统单个模态和综合模态均具有较好的检测和控制效果,被控模态具有较好的能控/能观性,所提出的优化准则和优化方法是可行的。     

Comparison of collocation strategies of sensor and actuator for vibration control

Some possible collocation strategies of sensor and actuator pairs for the application to active vibration control systems are analyzed, compared and discussed in this paper. This is becausea well-designed sensor — actuator collocation configuration can provide a simpler control algorithm with excellent performance and stability, especially when velocity feedback is adopted. As an ideal point collocation pair of a sensor and actuator shows high possibility in actual vibration control problems, the advantage of a collocated accelerometer — shaker pair is proven experimentally and discussed first. Then as a similar approach, a collocated piezosensor — piezoactuator pair is analyzed in depth with the in-plane motion coupling. Finally, two configurations of a practically collocated configuration with an accelerometer — piezoactuator pair and a non-overlapped collocated pair of a bimorph piezosensor — two bimorph piezoactuators are described in detail in terms of performance and stability with experimental results. Those two configurations are expected for the applications to more practical active control of vibration systems with the velocity feedback control scheme.     

A compressional-shear model for vibration control of beams with active constrained layer damping

In the modeling of the active constrained layer damping (ACLD) structures, the transverse displacements of the constraining layer and the host structures are usually assumed to be compatible. However, when performing active control, even a small difference between the transverse displacement of the constraining layer attached with actuator and that of the host structures bonded with sensor may destabilize the closed-loop control system. In order to understand the effect of incompatible transverse displacements, a model for the beam with ACLD in which both compressional vibration and shear damping are considered, is developed. In this model, the viscoelastic layer is modeled to carry not only the shear strain but also the peel strain. In addition, a thorough solution scheme to obtain the eigenvalues and frequency response of the closed-loop controlled beam is also given based on multiple shooting method. The effects of the compressional vibration on passive and active control are investigated through simulation examples. It is found that the compressional vibration can significantly affect the frequencies and damping ratios of higher-order modes of an actively controlled beam and may even destabilize the active control.     

Dynamic response analysis of closed-loop control system for random intelligent truss structure under random forces

Considering the randomness of structural damping, physical parameters of structural materials, geometric dimensions of active bars and passive bars, applied loads and control forces simultaneously, the problems of dynamic response analysis of closed-loop control system based on probability for the random intelligent truss structures are studied in this paper. The computational expressions of numerical characteristics of structural dynamic response of closed-loop control system are derived by means of the mode superposition method. Through the engineering examples, the influences of the randomness of them on structural dynamic response are inspected and some significant conclusions are obtained.     

柔性结构振动控制的初步分析与试验研究

采用智能结构的原理和方法,对压电元件用于柔性结构振动控控制的有关问题进行了初步探讨。对压电驱动器与结构的匹配关系进行了理论分析,对模态传感－驱动器对在柔性悬臂板结构中的布置数量和位置进行了优化设计,并对结构振动进行了控制试验,验证了该方法的有效性。     

结构滤波器在望远镜主轴控制系统中的应用

为了提高望远镜控制系统的闭环带宽和动态性能,研究了结构滤波器对控制系统闭环性能的影响。根据望远镜机械跟踪架的弹簧质量模型推导了系统的传递函数,分析了电机和负载转动惯量与谐振频率的关系,设计了基于系统开环频率特性的结构滤波器。将设计的结构滤波器串联入控制回路,用于减小机械谐振的幅值。介绍了结构滤波器的设计方法,以及加入结构滤波器后对控制系统闭环性能的影响。最后,在2m望远镜跟踪架转台上进行了验证实验。结果表明,加入结构滤波器后系统的闭环带宽由10Hz提高到了13 Hz,有效地抑制了速度的稳态谐振,提高了望远镜控制系统的速度跟踪性能。得到的实验结果验证了结构滤波器能够有效地提高系统的动态性能。     

Vibration Control of a Composite Beam Using Self-sensing Semi-active Approach

Structural vibration control was an active research area for the past twenty years because of their potential applications in aerospace structures,civil structures,naval structures,etc.Semi-active vibration control methods based on piezoelectric actuators and synchronized switch damping on inductance(SSDI) techniques attract the attention of many researchers recently due to their advantages over passive and active methods.In the SSDI method,a switch shunt circuit is connected to the piezoelectric patch to shift the phase and amplify the magnitude of the voltage on the piezoelectric patch.The most important issue in SSDI method is to control the switching actions synchronously with the maximum vibration displacement or maximum strain.Hence,usually a displacement sensor is used to measure the vibration displacement or a collocated piezoelectric sensor is needed to measure the strain of the structure near the piezoelectric actuator.A self-sensing SSDI approach is proposed and applied to the vibration control of a composite beam,which avoids using a separate sensor.In the self-sensing technique,the same piezoelectric element functions as both a sensor and an actuator so that the total number of required piezoelectric elements can be reduced.One problem in the self-sensing actuator,which is the same as that in the traditional collocated piezoelectric sensors,is the noise generated in the sensor signal by the impact of voltage inversion,which may cause extra switching actions and deteriorate control performance.In order to prevent the shunt circuit from over-frequent on-and-off actions,a simple switch control algorithm is proposed.The results of control experiments show that the self-sensing SSDI approach combined with the improved switch control algorithm can effectively suppress over-frequent switching actions and gives good control performance by reducing the vibration amplitude by 45%,about 50% improvement from the traditional SSDI with a separate piezoelectric element and a classical switch.     

基于同位加速度负反馈的振动主动控制研究

基于同位加速度传感/压电驱动的反馈方法,对用扬声器进行声激励的四面固支铝板开展多模态振动主动控制研究。根据实验模态分析的结果,确定了传感和驱动的位置。经过压电片传感/压电片驱动和加速度传感/压电片驱动两种方案的对比,选择了能观性和能控性较好的加速度传感方式。在正位置反馈控制律（positive position feedback,简称PPF）的基础上,以加速度信号进行反馈控制律的设计,提出基于加速度负反馈控制方案 (negative acceleration feedback,简称NAF),并对其进行稳定性和控制机理分析。控制时以加速度信号作为评价指标,对64和158 Hz两个模态分别进行单模态和多模态控制。结果表明,基于加速度的反馈控制可以大幅度降低铝板的振动,最大控制效果可达11 dB,远大于PPF的控制效果,对单模态和多模态均能实现有效的振动控制。     

Robust and minimum norm partial quadratic eigenvalue assignment in vibrating systems: A new optimization approach

The partial quadratic eigenvalue assignment problem (PQEVAP) concerns reassigning a few undesired eigenvalues of a quadratic matrix pencil to suitably chosen locations and keeping the other large number of eigenvalues and eigenvectors unchanged (no spill-over). The problem naturally arises in controlling dangerous vibrations in structures by means of active feedback control design. For practical viability, the design must be robust, which requires that the norms of the feedback matrices and the condition number of the closed-loop eigenvectors are as small as possible. The problem of computing feedback matrices that satisfy the above two practical requirements is known as the Robust Partial Quadratic Eigenvalue Assignment Problem (RPQEVAP). In this paper, we formulate the RPQEVAP as an unconstrained minimization problem with the cost function involving the condition number of the closed-loop eigenvector matrix and two feedback norms. Since only a small number of eigenvalues of the open-loop quadratic pencil are computable using the state-of-the-art matrix computational techniques and/or measurable in a vibration laboratory, it is imperative that the problem is solved using these small number of eigenvalues and the corresponding eigenvectors. To this end, a class of the feedback matrices are obtained in parametric form, parameterized by a single parametric matrix, and the cost function and the required gradient formulas for the optimization problem are developed in terms of the small number of eigenvalues that are reassigned and their corresponding eigenvectors. The problem is solved directly in quadratic setting without transforming it to a standard first-order control problem and most importantly, the significant “no spill-over property” of the closed-loop eigenvalues and eigenvectors is established by means of a mathematical result. These features make the proposed method practically applicable even for very large structures. Results on numerical experiments show that the proposed method considerably reduces both feedback norms and the sensitivity of the closed-loop eigenvalues. A study on robustness of the system responses of the method under small perturbations show that the responses of the perturbed closed-loop system are compatible with perturbations.