This paper studies the dynamics and control of a flexible manipulator system with a time-delayed acceleration feedback. Based on the singular perturbation method, the flexible manipulator system is decomposed into a slow subsystem describing the nonlinear rigid-body motion and a fast subsystem characterizing the flexible vibration. A torque controller is proposed to realize the trajectory tracking in joint space. Considering the inherent time delay introduced by the low-pass filter, a time-delayed acceleration feedback controller is developed to suppress the vibration of flexible links within the reciprocal state-space framework. Numerical simulations are conducted to validate the effectiveness of the proposed control method in set-point regulation and periodic vibration suppression. A physical experiment is designed and the experimental observations are in good agreement with theoretical predictions and numerical simulations. The obtained results show that the proposed control method achieves simultaneous trajectory tracking and vibration suppression with low computational complexity and good engineering applicability, providing an effective strategy for high-precision control of flexible manipulators.

This paper presents a metamaterial beam with the nonlinear magnetic mass-beam (NMMB) resonators to achieve certain tunable bandgaps. The metamaterial beam consists of the upper and lower faceplates and the periodically arranged NMMB resonators. The dispersion relation of the infinite-size beam is derived via the energy method. The governing equations of motion of the beam with finite length are obtained based on the Galerkin method. An experiment is designed and the revealed phenomena reach a good agreement with the theoretical analysis and numerical simulations. The results show that the tunable bandgaps are associated with the external excitation amplitude. As the amplitude of the excitation varies, the location and width of the bandgaps can be adjusted according to the frequency shift and multi-bandgap effects. Moreover, the influences of the thickness of the faceplates and the stiffness of cantilevers in the resonators on the bandgaps are shown.

机电控制系统受振动影响易发生故障,严重影响飞行安全,本文通过颗粒阻尼器对机电控制系统进行振动抑制研究,采用离散元仿真方法研究阻尼器的耗能变化规律与振动幅值、振动频率和颗粒数量的影响关系,并通过BP神经网络对颗粒阻尼器耗能数据进行训练和预测;通过机电控制器的随机振动试验,验证离散元仿真结论与BP神经网络预测模型的准确性.结论表明,离散元仿真在振动频率20～40Hz、激励幅值2～16mm范围内,其他条件一定时,阻尼器耗能随频率和幅值的增大而增大,随颗粒填充率先增大后减小,在57％～70％填充率范围内具有最佳耗能效果;在机载系统随机振动试验中,颗粒阻尼器填充率处于30％～90％范围内均表现出较好的振动抑制效果.仿真和试验结果对颗粒阻尼器在机电控制系统中进一步应用具有指导意义.

This paper investigates the problem of modeling and controlling a space manipulator system with flexible joints and links. The dynamic model of the flexible manipulator system is derived by using the Lagrange equation and the floating frame of reference formulation, where the assumed mode method is adopted to discretize flexible links, while the flexible joints are regarded as linear torsion springs. The natural characteristics of a single flexible link manipulator, under three different boundary conditions, are compared to reveal the effect of the flexibility of joints on the manipulator system and to choose suitable assumed modes. Furthermore, singular perturbation theory is introduced to decompose the system into a slow subsystem that describes the rigid-body motion, and a fast subsystem that describes the elastic vibration. Since the system is underactuated, a compound control strategy, which consists of the underactuated computed torque controller and the adaptive fuzzy controller, is presented to improve the accuracy of the trajectory tracking of the flexible joints and to suppress the elastic vibration of the flexible links, in the meantime. Both numerical simulation and experimentation are performed to verify the effectiveness of the proposed compound controller, and a comparison with the proportional-derivative (PD) controller is provided to highlight its superiority in suppressing the residual vibration of the tip.

The problem of modeling and controlling of a free-floating space manipulator with flexures in both links and joints is addressed in this study. A mathematical model of the system is developed by combining Lagrange’s equations and momentum conservation. The finite element method is introduced to discretize multi-links with complex cross-sections. In order to reduce the dimensions and maintain the precision of a rigid-flexible coupled system, an iterated improved reduction system method is adopted. Then, a novel composite control scheme for the reduced system is presented that uses the concept of integral manifolds and singular perturbation theory. Finally, an augmented computed torque controller is applied to the under-actuated slow subsystem to realize trajectory tracking in joint space, while a linear-quadratic controller is designed to damp out the vibration of joints and links. Numerical simulation results verified that the proposed hybrid controller can successfully suppress vibration and track trajectory at the same time.

随着飞机液压系统的高压、高功率化发展,液压管路的振动问题开始凸显出来,降低液压管路的振动,对于提高飞机航行安全性具有重要意义.本文针对航空液压管路进行振动特性研究,获得管路振动固有频率随内部压力和流速的变化规律,进一步根据液压管路动力学参数可变的特点,设计刚度可调的半主动吸振装置,建立适合复杂系统动力学响应分析的多软件联合仿真方法,验证吸振装置和半主动控制算法的振动抑制效果.仿真结果表明,半主动振动控制方法对液压管路系统的振动能够起到有效的抑制作用,在吸振器有效频率范围内管路振动衰减能够达45dB以上.

航空航天器结构在长期服役过程中,受到各种因素影响,存在各种飞行安全问题.针对连杆结构服役过程中存在的扭转弯曲工况,提出一种曲率信息计算优化方法,借助光纤Bragg传感器反演结构扭转弯曲变形.此方法能够减小杆件弯扭变形过程中因光栅栅区尺寸因素导致的数据测量误差,进而提升变形反演精度提升.ANSYS Workbench有限元仿真结果表明,这种方法与传统曲率递推变形反演方法相比,能够将扭转/弯曲变形条件下杆件变形监测与反演平均误差减小8％.小角度扭转/弯曲试验结果显示,进行曲率信息计算优化方法修正后反演所得变形量相对误差较修正前减小3.3％.研究结果表明,所提方法适用于杆件结构扭转变形监测场合,能够为未来航空器结构服役状态感知与自适应调整提供帮助.

In this paper, we study the nonlinear dynamics of a multiplex system consisting of neuronal networks each with an arbitrary number of FitzHugh-Nagumo neurons and intra-connections and delayed couplings. The network contains an autaptic connection formed by the axon of a neuron on its own soma or dendrites. The stability and instability of the network are determined and the existence of bifurcation is discussed. Then, the study turns to validate the theoretical analysis through numerical simulations. Abundant dynamical phenomena of the network are explored, such as coexisting multi-period oscillations and chaotic responses.

The design problem of a discrete controller with time delay and acceleration feedback for a single-link flexible manipulator system is addressed in this paper. The dynamical model of a single-link flexible manipulator system is presented by the adoption of the finite element method and Lagrange’s equation. Based on the random-walk process and the discrete reduction method, an augmented discretized delay-free state derivate space equation containing the random noise is established. An acceleration-based Kalman filtering method is developed in order to estimate the system state and external excitation necessary for the controller design. In light of the estimated augmented states, a hybrid controller that combines a feedback control algorithm and a feedforward control algorithm is designed according to optimal control theory and Moore–Penrose theory. Numerical simulation results show that the proposed controller can damp out the vibration response of the flexible manipulator system effectively upon external excitations. Moreover, it is further revealed that the control performance of the presented method can be improved by adding the time delay appropriately.

根据轴力变化对悬臂式结构固有频率的改变规律,设计一种由压电材料驱动的刚度自调谐动力吸振器.首先,研究适用于这类吸振器的半主动控制方法,分别采用逐步寻优和遗传控制算法对吸振器固有振动频率进行实时调节;其次,结合实际受控系统进行动力学仿真分析;最后,在获得有效振动抑制的基础上进一步将吸振器应用于风洞测力模型的振动控制试验研究.试验结果表明:吸振器能够将风洞测力模型端部振动抑制效果提高至40 dB以上,与其他类型的振动控制器相比具有更为优异的动力学性能.

This paper presents a finite-element (FE) model of a manipulator with a flexible link and flexible joint as well as embedded PZT actuators and proposes a corrected rebuilt reduced model (CRRM) to make its dynamic characteristics more consistent with reality and facilitate control design. The CRRM considers the holding torque of the manipulator driving motor and eliminates the response divergence induced by a fault of the mass matrix of the FE model. In order to reduce the dimensions and maintain the precision of the model, an iterated improved reduction system (IIRS) method is adopted. Additionally, a LQR controller is designed based on the output function of the improved model. The simulation results demonstrate that the CRRM is consistent with reality and the active controller has good performance in suppressing vibration of the manipulator with both the flexible link and the flexible joint.

Abstract In this paper, Monte Carlo method combined with the random critical-core probability model is proposed to calculate the longitudinal tensile strength of unidirectional composites. This method considers two-dimensional distribution of fibers on the cross-section, while the theoretical analysis method only takes the linear distribution of fibers into account. Using the weakest link principle, the failure probability and average strength of the unidirectional composites are obtained. The results show that the calculated values of longitudinal tensile strength of T300/5208 composite and unidirectional C/C composites agree well with the experimental results.

针对车载系统行进过程中产生的结构振动,提出被动隔振和主动减振相结合的方法对结构弹性振动和刚体振动进行抑制.一方面,针对结构弹性振动,在车载结构和车体之间安装隔振装置,选择合适的隔振器参数,对车载结构的弹性振动进行隔离.另一方面,结合刚体振动抑制的需求,进一步研究小阻尼隔振器带来的结构低频刚体振动.对隔振器和车载结构形成的新系统采用主动控制方法设计最优控制器,对这一类过驱动控制系统进行主动控制研究.通过主被动控制结合,实现车载结构全频段范围内的振动抑制,能够将系统刚体振动的位移均方根值抑制到无控制时的5％以下.

The H∞ robust control on a rear-sting wind tunnel model was experimentally studied.Due to that the model is suffering from external disturbance,an Eigensystem Realization Algorithm (ERA ) was used for model identification.In order to obtain a stable and robust system,a H∞ hybrid sensitivity optimization controller was designed to suppress the vibration of first two modes of the structure.The results of experiments indicate that the controller based on ERA model identification method is effective for vibration suppressing,and the vibration amplitude of first two modes is reduced to less than 1 0% compared to uncontrolled state.

This paper addresses the design problem of a discrete controller with time delay and acceleration feedback. The delta operator is firstly used to describe the discrete acceleration signal and convert the delayed continuous-time state equation into the delayed discrete-time system. Then the delayed discrete-time system is transformed into the delay-free one by applying a discrete reduction method. Based on the delay-free discrete-time system, the optimal output delta state feedback controller is designed by minimizing a discrete non-standard quadratic performance index and the feedback gain of the controller is obtained by a convergent algorithm. On the basis of the optimal output delta state feedback controller, the discrete time-delayed acceleration feedback controller is achieved by using the inverse reduction method, and the corresponding recursive control algorithm is developed. The controller saves the process of performing numerical integration and eliminating direct current and trend term in designing the displacement or velocity feedback control, so as to make the closed-loop system become simpler. Moreover, it can solve the problem of phase shift of the measured signal caused by time delay. The proposed controller with a low order model-based control algorithm is implemented on a smart cantilever beam with an accelerometer and piezoelectric actuator for different controller gain-delay combinations, and the control performance is evaluated. Simulation and experimental results demonstrate that the controller can effectively reduce the free vibration response of the smart cantilever beam.

This paper addresses the design problem of the controller with time-delayed acceleration feedback. On the basis of the reduction method and output state-derivative feedback, a time-delayed acceleration feedback controller is proposed. Stability boundaries of the closed-loop system are determined by using Hurwitz stability criteria. Due to the introduction of time delay into the controller with acceleration feedback, the proposed controller has the feature of not only changing the mass property but also altering the damping property of the controlled system in the sense of equivalent structural modification. With this feature, the closed-loop system has a greater logarithmic decrement than the uncontrolled one, and in turn, the control behavior can be improved. In this connection, the time delay in the acceleration feedback control is a positive factor when satisfying some given conditions and it could be actively utilized. On the ground of the analysis, the developed controller is implemented on a cantilever beam for different controller gain–delay combinations, and the control performance is evaluated with the comparison to that of pure acceleration feedback controller. Simulation and experimental results verify the ability of the controller to attenuate the vibration resulting from the dominant mode.

In wind tunnel testing, the test model is usually mounted by an axially supported beam inserted at the rear. The whole structure of the test model and the support is flexible with low natural frequencies. In transonic testing with a large angle of attack, the low-frequency pulsating pressure by airflow can easily cause the pitching vibration of the model with low frequency and large amplitude, which can lead to poor accuracy of measurement and fatigue damage of the test device. In this article, a FEM model is established for the transonic wind-tunnel testing model with its rear supported by a beam. Using balancing and modal truncation methods, the order of the model can be reduced. According to the feature of low-dimension, low-order and flexible structure of the model, an H∞ robust control method is used to fulfill the active vibration suppression of the low-frequency pitching vibration of the model. Simulation and analysis show that this active vibration suppression strategy is applicable and efficient, and has practical significance for the analysis of large complex flexible structures.

This research is focused on the vibration control problems of the continuous distributed structure suffering from complex excitations. According to the acute displacement vibration which induced by first mode of the structure, design a single input and single output (SISO) control system. A high-order filter is introduced to process the high-frequency disturbance included in the output signal. In order to keep stable, the nonlinear time delay of the filter is discussed, and a forecasting method for eliminating the time delay is deeper studied. For getting the constant time delay system, the phase compensation method is induced for eliminating the nonlinear characteristic of the filter's time delay. The forecasting method is performed effectively through establishing an ARMA model, and the coefficients of the model are defined by stochastic approximation method. A wind-tunnel model with rear sting is used as a distributed structure in experiments. The results reveal that the first mode vibrations of the model are effectively suppressed by this controller when the structure suffers complex excitations.

The aim of this study is to develop a method of active control based on time delay compensation for the low-order modes of a cantilever-like structure suffering from complex excitations. The time delay is induced by an anti-aliasing filter and a high-order digital low-pass filter, which are introduced to prevent frequency aliasing and observation spillover. However, approaches for time delay processing in active control systems have in the past been model dependent. This paper adopts a velocity feedback control law to increase system damping, and constructs an autoregressive moving average (ARMA) model for eliminating the time delay caused by filters. The ARMA model is model-free and its coefficients are adjusted adaptively according to the outputs of the system. In practical applications, the direct current (DC) excursion induced by the calculation is also considered, and a proper method of DC cancellation is adopted. A wind-tunnel model with rear sting is used as a cantilever-like structure in the experiments. The results reveal that the first mode vibrations of the model are effectively suppressed by this controller when the structure suffers from complex excitations.

The aim of this study was to investigate a method of active vibration control based on input estimation with a test method.The control method depended on parameters and external disturbance of a controlled system.In order to establish a dynamic equation of the system with unknown parameters,an algorithm of model identification was introduced to identify the parameters firstly.And then,the system disturbance was described as a discrete recursive expression with the random walk model and used to construct a new state equation as an auxiliary state variable.According to the methods of Kalman filtering and linear quadratic Gaussian(LQG),the control algorithm based on the new state equation was built.Therefore,the system objective function was created according to the new state vectors including disturbance,state variables and control inputs.Finally,the values of the current control input could be obtained with the optimal algorithm.The method was validated in an example of a cantilever beam model.The results revealed that the proposed method is better than the conventional LQG method.