一个非线性系统的控制律计算及仿真

针对柔性机械臂非线性系统的模型，采用非线性状态反馈局部解耦和基于非线性泛函在给定函数附近线性展开的思想，导出了一种使系统沿期望轨迹运行的控制律计算方法，仿真与实验结果验证了其有效性。     

一种新型柔性夹持高频超声换能器设计

为了提升高频超声换能器输出振幅与超声能量的传输效率,该文提出了一种新型柔性夹持高频超声换能器,并基于模块化设计思想,综合机电等效法、四端网络、有限元分析及柔度分析技术,系统建立了此类型高频超声换能器的设计方法,制作了换能器样机,搭建了换能器电学、动力学特性测试平台。激振实验表明,柔性夹持换能器输出端稳态振幅较传统夹持换能器提升了38.55%。换能器输出端动态振幅信号时域、频域分析结果表明,将柔性铰链机构和传统法兰夹持结构相结合,通过引入柔性转动副,柔性夹持换能器超声能量传递效率提高了5.16%。这表明柔性夹持法兰能够提升夹持结构的运动解耦能力,具有一定的应用前景。     

PID神经网络在飞控解耦中的仿真研究

在进行飞行控制律设计时,为了获得好的控制品质,有必要对各输出量进行解耦,并且使控制器能根据被控对象动力学特性的改变而自适应调整。为此,介绍了两种PID神经网络解耦控制结构和一种神经网络辨识器,并分别给出了PID神经网络解耦控制器和辨识器的前向算法及反向传播算法;最后分别应用两种解耦方法针对飞机横侧向线性模型进行计算仿真,得到了两种解耦结果;证明了PID神经网络解耦控制的有效性,并比较了两种结构的优缺点。     

直接力/气动力复合控制导弹通道耦合特性分析及其解耦控制

建立了复合控制空空导弹俯仰/偏航两个通道间的耦合近似线性动力学模型.仿真分析了主要耦合因素对导弹动态特性的影响,同时基于输出反馈特征结构配置解耦控制算法对其进行解耦,对比仿真结果,说明该算法对于参数变化不明显、干扰不大的系统解耦效果比较好,下一步需要研究具有强鲁棒性的复合控制解耦算法.     

一种基于对角递归神经网络的PID解耦控制器

在PID多变量解耦控制的基础上,设计了一种基于对角递归神经网络的PID解耦控制器。基于对角递归神经网络构造了PID控制器,并把几个PID控制器平行采用作为解耦控制器,以同时实现解耦和控制功能。通过对2输入2输出非线性耦合对象进行计算机仿真结果表明,该控制器对多变量非线性系统解耦控制效果很好。     

双环掺铒光纤激光器混沌的耦合反馈相移控制

提出了双环掺铒光纤激光器混沌耦合反馈相移控制方法和物理模型,利用耦合器将系统的输出量反馈到系统中,选取适当的反馈系数,并在反馈通道上加入相移控制器PC控制反馈光的相移,通过对反馈系数和反馈光相移的控制可以实时、动态、有效地控制激光混沌到稳定态和周期态;结合混沌耦合反馈相移控制方法和物理模型,建立了该控制模型的动力学方程;运用数值计算分析了系统输出状态随着控制参数变化的演化规律,表明控制参数反馈系数和反馈光相移的变化可以使系统的输出产生丰富的具有一定规律性的激光动力学现象;最后讨论了混沌被控制到单周期态时系统输出的振荡周期的变化规律与控制量的关系,在选取适当的控制参数,快速达到所需输出状态时,可以充分利用这一关系。     

基于α阶逆解耦的多变量内模控制系统研究

由于工业过程控制中存在大时滞现象,使得单变量内模控制难以获得有效的控制,而多变量内模控制成为一种较好的控制策略。文中简单介绍了多变量内模控制的原理,分别基于主回路为控制对象、V规范解耦的原则和α阶逆解耦进行内模控制器的设计,阐述了各个控制器的主要思想及其设计的具体方法。通过仿真比较模型匹配与模型失配下的内模控制输出仿真图。由仿真结果可以得出,基于V规范解耦的内模控制器具有较好的控制效果,但是解耦效果存在缺陷,针对非线性系统提出的基于α阶逆解耦的内模控制系统具有较好的解耦和控制效果。     

一种静不稳定无人机快速跃升与俯冲机动控制器设计

针对无人机在快速跃升与俯冲机动中存在的气动耦合、操纵耦合与不确定扰动,以及由于静不稳定性而造成的不稳定俯仰力矩等问题,提出了一种新的鲁棒模型参考自适应非线性逆控制器。首先,通过基于状态反馈的非线性逆控制完成多通道之间的解耦;然后,依据解耦后的线性闭环系统设计鲁棒模型参考自适应控制器,其主要作用是对非线性逆误差与不稳定俯仰力矩进行补偿,并对不确定扰动进行抑制,从而保证无人机在整个快速机动飞行中的稳定性。通过非线性仿真验证了该控制方法在快速跃升与俯冲纵向机动控制中的有效性与可靠性,并与典型的鲁棒伺服LQR最优控制器对比,说明了该控制器的解耦性能以及对于不确定扰动的抑制作用。     

双向压电驱动的二维快速伺服刀架

快速伺服刀架能够提供精确、快速的微纳米级运动.为了获得双向和二维运动,该文研制了一种双向压电驱动的二维快速伺服刀架.该刀架采用对称结构设计,结合柔顺放大机构和位移解耦机构,末端执行机构实现较大的输出位移,同时减小耦合位移.基于伪刚体模型,建立快速伺服刀架的静力学和动力学模型,得到机构的输出位移、输出耦合比、最大应力和固...     

压电智能应用于柔性悬臂梁振动控制系统研究

基于模糊控制的振动控制方法,针对柔性悬臂梁,设计了相应振动控制器。采用电桥电路法分离出压电自感知执行器的感知信号,通过传感器将采集进来的信号,由最优控制理论离线计算得到理论输出值。并将理论输出值与对应的系统输入值对应起来,从而建立拥有最优解的模糊控制规则表。通过传感器采集系统状态并经过处理得到输出信号,作用于执行器上对柔性梁的振动进行抑制。仿真结果表明,采用的控制器对于改善振动快速控制是非常有效的。     

Design,dynamic modelling and experimental validation of a new three-degree-of-freedom flexible arm

This article describes the design, dynamic modelling and experimental validation of a new three-degree-of-freedom flexible arm which is suitable for industrial applications. The arm was designed on the assumption that all its mass was concentrated at the tip. In keeping with this, the arm was built with very lightweight links, and all the actuators were located at its base. A second feature is a special mechanical configuration that approximately decouples radial tip motion from angular tip motions; i.e. the first actuator produces an azimuthal movement, the second actuator produces an elevation movement and the third produces an approximately radial movement. From the dynamics point of view, this new mechanism also decouples the forces transmitted by the actuators to the tip of the arm, i.e. the torque generated by each actuator produces a tip force which is orthogonal to the forces produced by any of the other actuators. On the assumption that all the mass is concentrated at the tip, a compliance matrix can be used to model the oscillations of the structure. Then, dynamics of the arm becomes very simple (a lumped single mass model instead of the usual distributed mass model), and its control system can be significantly simplified: minimum sensing effort is required (only motor and tip measurements are needed), and PID controllers combined with a dynamic inversion subsystem can be used. These design specifications have been experimentally validated on the prototype we have built. Experimental identification of the dynamics has confirmed the validity of the assumption of a single mass concentrated at the tip. A flexible manipulator of simplified dynamics has been built and tested which is much lighter than equivalent standard industrial robots.     

基于坐标变换的武器平台运动模拟

利用坐标转换技术提出了一种武器平台运动模拟方法,建立了直线、折线运动模型,并根据所建立的模型实时计算目标运动轨迹,实现了航迹的动态推演。     

Cellular Neural Networks With Transient Chaos

A new model of cellular neural networks (CNNs) with transient chaos is proposed by adding negative self-feedbacks into CNNs after transforming the dynamic equation to discrete time via Euler's method. The simulation on the single neuron model shows stable fix points, bifurcation and chaos. Hence, this new CNN model has richer and more flexible dynamics, and therefore may possess better capabilities of solving various problems, compared to the conventional CNN with only stable dynamics     

Limited-state commands for systems with two flexible modes

This paper generates command profiles to reduce residual vibration for rest-to-rest motion of flexible systems with two-modes. The commands are limited-state, in that they contain only two positive and two negative valves. This allows them to be utilized with simple on–off, or limited-state actuators. A great advantage of the command profiles is that they are described by closed-form functions. The commands are designed by first canceling the two-modes of flexible vibration and then satisfying a secondary constraint to arrive at the desired target location as quickly as possible. The performance of the control method is evaluated as a function of move distance, actuator effort, maximum transient deflection, and robustness to modeling errors. The control method is illustrated with a numerical simulation of a two-mode system. It is also experimentally validated on a portable bridge crane with double-pendulum dynamics.     

Finite-Difference Modeling of Micromachine for Use in Gastrointestinal Endoscopy

An on-going research project is to develop a micromachine driven actively and wirelessly by external magnetic field. The micromachine has great potential for being used in medical fields such as gastrointestinal endoscopy. The ultimate goal is to develop a control mechanism capable of moving the wireless endoscope through the human's gastrointestinal tract in any direction with minimum level of harm to human body. This paper establishes fluid dynamics model suitable for micromachine's movement in intestinal tract, simulates pressure distributions of micromachine's surface, and further calculates driving and load torques. Based on the fluid simulation results, parameters for generating appropriate rotating magnetic field can be calculated. This fluid dynamics simulation method provides a novel approach to analyze biomedical micromachine's mechanical properties under external electromagnetic equipment.     

A Simple Model-Based Approach for Fluid Dispensing Analysis and Control

In this paper, a simple model-based approach is presented for modeling and control of the fluid dispensing. A simple model structure is derived from the pipe flow, which has the capacity to handle both Newtonian and non-Newtonian fluids. When working for unknown dynamics, parameters of the model need to be estimated from the process data. Using a simple and effective approximation method, proper operating conditions for parameter estimation can be figured out. The feasibility of this simplified model is evaluated in comparison with computational fluid dynamics for both known and unknown dynamics. Both simulation and real experiment demonstrate simplicity and effectiveness of the proposed model and its estimation method for both the steady and unsteady fluid dispensing. Based on this simple and effective model, a realistic model-based run-by-run control can be developed effectively to achieve a robust dispensing performance. Both simulation and real experiment have shown that the disturbance from the fluid variation is minimized, and the dispensing consistency is improved greatly.     

基于接触动力学的座圈动态响应仿真分析

座圈是履带车辆上的一个关键件,根据接触动力学理论,对座圈子系统的动态响应进行了分析研究。首先结合有限元和多体动力学分析技术,创建面向柔性下座圈的整车刚柔混合模型。考虑座圈子系统中座圈与滚珠的动态接触关系,采用边界盒法搜索上座圈—滚珠—下座圈之间的接触状态,由Hertz接触理论建立非线性弹簧阻尼模型计算接触力。然后以典型工况下座圈动态响应分析为例,对整车样机进行接触动力学仿真分析,获得了柔性下座圈的应力分布及变化情况。     

Control-faced dynamics with deformation compatibility for a 5-DOF active over-constrained spatial parallel manipulator 6PUS–UPU

Taking into account the effect of structural compliance, inverse dynamics of the active over-constrained parallel manipulator 6PUS–UPU with five degrees of freedom is solved in this article. Firstly, the relationship between driving forces and actuated force screws of each limb is derived. Then the coordination of elastic deformation between limbs which consider the effect of gravity and inertia is acquired. Finally the unique solution of driving forces for the active over-constrained parallel manipulator is derived by incorporating the force equilibrium equation of the moving platform. To validate the theoretical derivation, dynamics simulation model of manipulator based on rigid–flexible mixed structure is shown and numerical examples are given. Comparison with the traditional method of dynamics based on pseudo-inverse is also made. Finally, a feasible experimental method, as an effective test to the theoretical calculation, is proposed and applied on the prototype.     

A state-space modeling approach for localization of focal current sources from MEG

State-space modeling is a promising approach for current source reconstruction from magnetoencephalography (MEG) because it constrains the spatiotemporal behavior of inverse solutions in a flexible manner. However, state-space model-based source localization research remains underdeveloped; extraction of spatially focal current sources and handling of the high dimensionality of the distributed source model remain problematic. In this study, we propose a novel state-space model-based method that resolves these problems, extending our previous source localization method to include a temporal constraint by state-space modeling. To enable focal current reconstruction, we account for spatially inhomogeneous temporal dynamics by introducing dynamics model parameters that differ for each cortical position. The model parameters and the intensity of the current sources are jointly estimated according to a bayesian framework. We circumvent the high dimensionality of the problem by assuming prior distributions of the model parameters to reduce the sensitivity to unmodeled components, and by adopting variational bayesian inference to reduce the computational cost. Through simulation experiments and application to real MEG data, we have confirmed that our proposed method successfully reconstructs focal current activities, which evolve with their temporal dynamics.     

Object tracking with particle filtering in fluorescence microscopy images: application to the motion of neurofilaments in axons

Neurofilaments are long flexible cytoplasmic protein polymers that are transported rapidly but intermittently along the axonal processes of nerve cells. Current methods for studying this movement involve manual tracking of fluorescently tagged neurofilament polymers in videos acquired by time-lapse fluorescence microscopy. Here, we describe an automated tracking method that uses particle filtering to implement a recursive Bayesian estimation of the filament location in successive frames of video sequences. To increase the efficiency of this approach, we take advantage of the fact that neurofilament movement is confined within the boundaries of the axon. We use piecewise cubic spline interpolation to model the path of the axon and then we use this model to limit both the orientation and location of the neurofilament in the particle tracking algorithm. Based on these two spatial constraints, we develop a prior dynamic state model that generates significantly fewer particles than generic particle filtering, and we select an adequate observation model to produce a robust tracking method. We demonstrate the efficacy and efficiency of our method by performing tracking experiments on real time-lapse image sequences of neurofilament movement, and we show that the method performs well compared to manual tracking by an experienced user. This spatially constrained particle filtering approach should also be applicable to the movement of other axonally transported cargoes.