Modeling and free vibration behavior of rotating composite thin-walled closed-section beams with SMA fibers

Smart structure with active materials embedded in a rotating composite thin-walled beam is a class of typical structure which is using in study of vibration control of helicopter blades and wind turbine blades. The dynamic behavior investigation of these structures has significance in theory and practice. However, so far dynamic study on the above-mentioned structures is limited only the rotating composite beams with piezoelectric actuation. The free vibration of the rotating composite thin-walled beams with shape memory alloy(SMA) fiber actuation is studied. SMA fiber actuators are embedded into the walls of the composite beam. The equations of motion are derived based on Hamilton’s principle and the asymptotically correct constitutive relation of single-cell cross-section accounting for SMA fiber actuation. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin’s method. The formulation for free vibration analysis includes anisotropy, pitch and precone angle, centrifugal force and SMA actuation effect. Numerical results of natural frequency are obtained for two configuration composite beams. It is shown that natural frequencies of the composite thin-walled beam decrease as SMA fiber volume and initial strain increase and the decrease in natural frequency becomes more significant as SMA fiber volume increases. The actuation performance of SMA fibers is found to be closely related to the rotational speeds and ply-angle. In addition, the effect of the pitch angle appears to be more significant for the lower-bending mode ones. Finally, in all cases, the precone angle appears to have marginal effect on free vibration frequencies. The developed model can be capable of describing natural vibration behaviors of rotating composite thin-walled beam with active SMA fiber actuation. The present work extends the previous analysis done for modeling passive rotating composite thin-walled beam.     

柔性机器人动力学分析与振动控制研究综述

综述了柔性机器人动力学分析与振动控制的研究现状，对变形的描述、变形场的离散化、建模方法、近似分析减振结构设计及关节作动系统控制律设计等关键问题进行了详细阐述。     

Free vibration analysis of composite beams with two non-overlapping delaminations

An analytical solution to the free vibration of composite beams with two non-overlapping delaminations is presented. The delaminated beam is modeled as seven interconnected Euler-Bernoulli beams using the delaminations as their boundaries. The continuity and the equilibrium conditions are satisfied between adjoining beams. The analysis includes the differential stretching between the delaminated layers and the bending-extension coupling. The results of the present model agree well with the analytical and experimental data reported in the literature. Parametric studies show that the sizes and locations of the delaminations have significant effect on the natural frequencies and mode shapes. These results provide useful information in the study of the free vibration of delaminated composite beams.     

柔性冗余度机器人振动主动控制系统特性分析

研究了基于机敏材料的柔性冗余度机器人振动主动控制系统的可控性与可观性。建立了受控系统的状态空间表达式，提出了离散时变系统的可控性与可观性分析的简化判据，为设计状态反馈控制器与状态观测器以改善柔性冗余度机器人的动力学品质奠定了基础。最后，以具有一个位置冗余度的平面3R柔性机器人为例，进行了计算机仿真。     

超精密隔振平台主动振动控制系统设计

建立了超精密隔振平台的结构及动力学模型，设计了一种新型的双向电磁作动器，并采用PID控制算法建立了主动振动控制系统模型，经Matlab软件仿真分析表明，该系统具有良好的隔振效果。     

The investigation of unbalanced vibration in flexible motorized spindle-rotor system

Unbalance is a significant concern for spindle-rotor dynamic systems and an important problem in high-speed machining. An active control scheme with built-in force actuator is proposed for unbalanced vibration of flexible motorized spindle-rotor, which is to improve the performance of high-speed machining system. At first, the motorized spindle motor with built-in force actuator and flexible motorized spindle-rotor are designed and then the experiment setup based on digital signal processor for controlling actively the unbalanced vibration of flexible spindle-rotor is tailored. Finally, the active vibration control scheme is investigated experimentally based on previous theoretical studies. The experimental results prove the feasibility of the active control scheme.     

柔性梁谐波干扰的间接控制

我们研究一种低阶控制算法,用来控制空间柔性梁受到的轻微的、已知频率的谐波干扰。通过选择合适的控制增益,即可在系统的其它部分仍存在振荡的情况下,可以消除谐波干扰,使系统的输出趋于收敛,达到稳定。     

Active vibration μ-synthesis-control of a hydrostatically supported flexible beam

This paper presents active vibration control of a hydrostatically supported, flexible beam. The objective is to show the capability of active hydrostatic bearings, where the flow rate is controlled with a fast dynamic servo valve. Consequently the damping as well as the stiffness behaviour of the supported structure should be improved. First the damping behaviour is increased by using acceleration feedback in combination with the modern, robust control concept μ-synthesis. It enables to overcome undesirable properties of the mechatronic system as, weakly damped, low frequency flexible modes, phase lag, slight nonlinearities or non-collocation. To increase the stiffness of the bearings the oil gap is used as control variable and controlled to constant with PI-control. Finally, the obtained results are compared with the state-of-the-art technology of hydrostatic bearings.     

KBK柔性组合式悬挂起重机

介绍了德马格公司KBK柔性组合式悬挂起重机多样的产品型式和技术参数。阐述了柔性化、组合化和模块化是这种起重机的鲜明特点。     

Bending and vibration of circular cylindrical beams with arbitrary radial nonhomogeneity

This paper presents a new approach for analyzing transverse bending and vibration of circular cylindrical beams with radial nonhomogeneity. The radial nonhomogeneity may be continuous or piecewise-constant, corresponding a functionally graded circular cylinder or a multi-layered circular cylinder, respectively. Different from the Euler-Bernoulli and Timoshenko theories of beams, our analysis considers shear deformation, but does not need to introduce a shear correction factor. Using the shear-stress-free condition at the surface of the cylinder, coupled governing equations for deflection and rotation angle are derived, and then converted to a single governing equation. The influences of gradient index on the deflection and stress distribution for cantilever and simply-supported beams are studied. Natural frequencies of free vibration of a cylindrical beam with circular cross-section are calculated for different power-law gradients. In particular, a circular cylindrical shell may be taken as a special case of a bi-layered cylinder where the material properties of the inmost cylinder vanish. For this case, the natural frequencies for simply-supported and clamped-clamped cylindrical shells are evaluated and compared with those using three-dimensional theory. Our results coincide well with the previous.     

静压气浮溜板的振动主动控制系统研究

静压气浮溜板主要用在超精密加工机床中,它的振动将通过刀架直接反映到被加工工件表面,影响工件的表面质量。采用自行研制的空气作动器作为执行器,以实现无摩擦接触;采用神经网络-PID控制策略,通过BP神经网络在线学习调整PID控制参数,实现最佳参数组合。实验结果表明气浮溜板的振动主动控制系统是可行性的和有效性的。     

柔性自适应桁架结构的振动控制方法实验研究

为提高结构对外部环境的抗干扰能力,构造了空间柔性自适应桁架结构,并对其主动控制进行了研究。通过加速度传感器测量位移的实验,建立了由dSPACE数据采集与处理系统、压电传感器、压电作动器、桁架结构和微机实时测控组成的实时计算机控制系统。基于自适应桁架结构的有限元理论,采用改进的二次积分力反馈控制方法,研究了空间柔性自适应桁架结构的振动主动控制问题。通过正弦激励进行了实时控制实验,给出了控制前后节点18x方向的位移振幅抑制变化情况及功率谱响应曲线。实验研究结果表明,该控制方案对空间柔性结构的低频大幅振动有很好的控制效果。     

Coupled bending and torsional vibration of axially loaded thin-walled Timoshenko beams

A dynamic transfer matrix method of determining the natural frequencies and mode shapes of axially loaded thin-walled Timoshenko beams has been presented. In the analysis the effects of axial force, warping stiffness, shear deformation and rotary inertia are taken into account and a continuous model is used. The bending vibration is restricted to one direction. The dynamic transfer matrix is derived by directly solving the governing differential equations of motion for coupled bending and torsional vibration of axially loaded thin-walled Timoshenko beams. Two illustrative examples are worked out to show the effects of axial force, warping stiffness, shear deformation and rotary inertia on the natural frequencies and mode shapes of the thin-walled beams. Numerical results demonstrate the satisfactory accuracy and effectiveness of the presented method.     

基于鲁棒参数控制方法的可变控制线控制图

针对在制造过程中应用鲁棒参数控制时,其过程均值和方差都会经常改变,且无法直接使用现有的控制图技术进行统计过程控制,提出了基于应用鲁棒参数控制的可变控制线控制图的设计方法.它不同于传统的适应性控制图设计方法,是该研究通过对过程均值和方差变化的有效估计,给出了可变控制线的调节律算法,为控制图自动跟踪过程变化提供了一种可行的方法.通过实例分析,验证了上述方法的有效性和实用性.     

Modeling and bending vibration control of nonuniform thin-walled rotating beams incorporating adaptive capabilities

This paper addresses the problems of modeling and bending vibration control of tapered rotating blades modeled as nonuniform thin-walled beams and incorporating adaptive capabilities. The blade model incorporates non-classical features such as transverse shear, secondary warping and includes the centrifugal and Coriolis force fields. For the non-adaptive system, an assessment of a number of non-classical features including the taper characteristics is accomplished. The adaptive capabilities are provided by a system of piezoactuators bonded to the structure surface and spread over the entire span of the beam. Based on the converse piezoelectric effect and on the out-of-phase actuation, the piezoactuators produce a localized strain field in response to the applied voltage, and consequently, a change of the dynamic response characteristics is induced. A combined feedback control law relating the piezoelectrically induced transversal bending moment at the beam tip with the kinematical response quantities appropriately selected is used, and the beneficial effects upon the closed-loop dynamic characteristics of the blade are highlighted.     

含柔性吸附材料的攀爬机器人振动特性与稳定性分析研究

为了提升攀爬机器人壁面运动稳定性从而提高其工程应用能力。针对攀爬机器人壁面运动过程的振动与动力学耦合特性问题,本文设计制作了一种含柔性吸附材料的攀爬机器人。基于刚柔耦合原理,获得刚性体与柔性体运动学递推关系,利用拉格朗日原理建立攀爬机器人动力学方程。推导得到反应动力学耦合程度的数学模型。通过仿真分析得到运行相同位移情况下,通过调整加减速时间比例使得机器人振幅下降35%,分析得到一定范围内攀爬机器人刚性质量与吸附材料弹性模量增加通过降低动力学耦合程度降低攀爬机器人振动响应。通过样机实验测量了攀爬机器人负载能力与不同运动阶段真空度与流量的稳定性。研究为攀爬机器人的驱动控制策略与工程应用奠定基础。     

Adaptive robust vibration control with input shaping as a flexible maneuver strategy

An adaptive robust control is presented for the vibration reduction of a flexible spacecraft by combining the input shaping technique with the sliding-mode control. The combined approach appears to be robust in the presence of a severe disturbance and an unknown parameter which will be estimated by on-line least-square method. As a maneuver strategy, it is found that a synthesized trajectory with a combination of low-frequency mode and rigid-body mode results in better performance and is more efficient than the traditional rigid-body trajectory alone which many researchers have employed. The feasibility of the vibration control approach is demonstrated by applying it to a benchmark problem in aerospace. For the applications of the proposed technique to realistic flexible spacecraft systems, several requirements are discussed such as mode stabilization and enormously large system order.     

300 MW汽轮发电机组转子轴系弯振鲁棒控制研究

针对300 MW汽轮机组转子轴承系统,在建立其8支承9节点集总模型的基础上,对轴系最左端面和发电机右端面的弯曲振动响应进行研究.为避免运行过程中受到的各种激励形式造成的扰动,设计了一种鲁棒轨迹控制器,保证了跟踪误差的一致终值有界.最后,通过模拟仿真对所提出的鲁棒控制方案与开环控制方案进行了比较,结果表明鲁棒轨迹控制具有更高的控制精度和稳定性.     

柔性臂空间机器人的神经网络自适应控制及振动模态分级模糊控制

由于太空中的在轨作业一般要求空间机器人具有手臂长、负载大,对空间机器人动力学及控制进行分析时必须考虑到机械臂杆件的柔性问题。为此探讨了参数未知柔性臂空间机器人载体姿态、关节协调运动控制及柔性振动抑制问题。由系统动量守恒关系及假设模态法,利用Lagrange方法建立了漂浮基柔性臂空间机器人的系统动力学方程。运用奇异摄动理论的双时间刻度分解,导出了适用于控制系统算法设计的奇异摄动数学模型。利用该模型,针对慢时标子系统——等价刚性空间机械臂,设计了系统参数不确定情况下的径向基函数神经网络补偿控制算法,以控制柔性臂空间机器人的载体姿态及机械臂关节铰协调地来完成各自在关节空间的期望运动;神经网络控制算法的研究目的是基于神经网络良好的在线自学习能力,大大提高整个系统的控制精度。针对快时标子系统——柔性臂的振动,设计了分级模糊控制算法来主动抑制柔性杆的振动。分级模糊控制算法的研究目的是为了减少模糊规则库的大小,有效提高模糊控制器的计算效率。通过计算机仿真验证了提出方法的有效性和可行性。