Robust control of XYZ flexure-based micromanipulator with large motion

This article describes the development of an XYZ flexure-based micromanipulator, with the features of decoupled kinematic structure, large motion range, high positioning precision, and fast response. The large motion range of flexure mechanisms is quantified by a given definition. Based on the given definition, large motion is achieved in the mechanical design of the XYZ-flexure parallel mechanism (FPM). To ensure high positioning precision and fast dynamic response, a hybrid control algorithm with both position control and vibration control are designed, using the H_∞-theory. The controller strongly solves the three common problems of flexure mechanisms simultaneously, including unmodeled uncertainties, the external disturbances and vibration caused by inherent low damping.     

三支链六自由度并联柔性铰微动机器人的研究

提出了一种过程中采用的新型三支链六自由度并联微动机器人结构。采用两端分别带有柔性球铰和柔性旋转铰的支杆以简化结构,整体加工包含三个二自由度单元的基平台来有效减小装配误差,并用压电陶瓷驱动弹性平板获得高分辨率高精度。根据运动影响系数理论对其运动学进行分析,求出了其平动台、支杆和柔性铰链的速度表达式。考虑柔性铰链的弹性变形,基于虚功原理建立了其刚度模型。 分析了此类并联微动机器人的设计目标和柔性铰链设计原则,采用模块化精密定位控制器设计了控制系统。实验结果表明,所设计的微动机器人可达到纳米级精度, 简化了六支链六自由度并联微动机器人的复杂结构,减小了装配误差。     

T-Flex: A fully flexure-based large range of motion precision hexapod

Six degree of freedom manipulation provides full control over position and orientation, essential for many applications. However, six degree of freedom parallel kinematic manipulators (e.g. hexapods) either have a limited range of motion combined with a good repeatability when comprising flexure joints, or they have limited repeatability with a large workspace when using traditional rolling- or sliding-element bearings. In this paper, the design and optimization of a fully flexure-based large range of motion precision hexapod robot is presented. The flexure joints have been specifically developed for the purpose of large range of motion and high support stiffness for this manipulator. The obtained system allows for ±100 mm of translational and more than ±10° of rotational range of motion in each direction combined with a footprint of 0.6 m² and a height of 0.4 m. Furthermore, a dedicated flexure-based design for the actuated joints combines high actuation forces with the absence of play and friction, allowing for accelerations exceeding 10 g. Experiments on a prototype validate the sub-micron repeatability, which is merely limited by the selected electronics.     

Vitreous cryo-sectioning of cells facilitated by a micromanipulator

Sectioning vitrified cells and tissues for cryo‐electron microscopy is more challenging than room‐temperature sectioning of plastic‐embedded samples. As the sample must be kept very cold (相似文献   

Robust levitation control for maglev systems with guaranteed bounded airgap

The robust control design problem for the levitation control of a nonlinear uncertain maglev system is considered. The uncertainty is (possibly) fast time-varying. The system has magnitude limitation on the airgap between the suspended chassis and the guideway in order to prevent undesirable contact. Furthermore, the (global) matching condition is not satisfied. After a three-step state transformation, a robust control scheme for the maglev vehicle is proposed, which is able to guarantee the uniform boundedness and uniform ultimate boundedness of the system, regardless of the uncertainty. The magnitude limitation of the airgap is guaranteed, regardless of the uncertainty.     

含多提前期的不确定供应链网络的鲁棒控制

为了减少内外部不确定性因素和多种提前期对供应链网络系统运作效率的影响,研究了一种模糊鲁棒控制策略。研究了含多提前期的供应链网络系统在不确定环境下的鲁棒运作问题。基于离散Takagi-Sugeno模糊控制系统,考虑生产能力、供应链结构、顾客需求等内外部不确定因素和供应链网络系统的运作提前期,建立了含多提前期的不确定动态供应链网络的离散Takagi-Sugeno模糊模型。通过在每个最大交叠规则组中构建一个离散型分段Lyapunov函数并应用并行分布补偿原理,提出针对该模型的模糊鲁棒H∞控制策略,该控制策略可以抑制不确定性因素和提前期对供应链网络的影响,保证供应链网络鲁棒运作。通过一个仿真算例验证了该控制策略能使供应链网络总成本达到理想状态,从而表明了所提方法的实用性和有效性。     

基于频域分析的预测控制鲁棒性设计

从分析预测控制的内模机理出发，把系统稳定鲁棒性和品质鲁棒性要求作为内模控制器设计的两个约束条件，利用控制理论中频域分析的方法把离散控制系统的控制器设计转化到频域进行分析，推导出满足系统稳定鲁棒性和品质鲁棒性条件的内模控制器，从而得出预测控制鲁棒性设计的条件，使控制系统能较好的抑制外部扰动所产生的影响。仿真实验结果表明该设计比传统的CHR和Cohen-Coon整定算法有更优异的控制效果。     

纳米级精度柔性机器人的设计方法及实现研究

从材料、几何结构、柔性铰链、驱动器、运动与负载及加工等几个方面总结了面向精密作业的柔性机器人设计准则。对柔性机器人的设计方法进行了探讨。以精密作业中的具体应用为例，依据这些设计方法与准则，从机械本体和驱动器控制2个方面详细描述了可实现纳米级精度的3自由度柔性机器人样机设计的具体实现过程，设计结果满足任务要求。     

一种无耦合位移和低集中应力的二维微操作器研究

集中应力和耦合位移是影响基于柔性铰链和压电陶瓷驱动器的微操作器性能的关键因素。单平行四杆机构具有低的集中应力，但存在大的耦合位移，双平行四杆机构没有耦合位移但存在较大的集中应力。在分析上述2种经典微操作器机构优缺点的基础上，吸取每一种机构的优点，摈弃各自的缺点，构建了一种复合四杆机构，并对这3种机构进行了对比分析，用有限元仿真的结果证明了理论分析的正确性。本文还设计加工了3种类型的二维微操作器柔性铰链机构与压电陶瓷驱动组成二微维操作器，并进行了对比实验研究，实验结果表明，该复合四杆微操作器性能优于经典的平行四杆微操作器和双平行四杆微操作器。     

Robust adaptive precision motion control of hydraulic actuators with valve dead-zone compensation

This paper addresses the high performance motion control of hydraulic actuators with parametric uncertainties, unmodeled disturbances and unknown valve dead-zone. By constructing a smooth dead-zone inverse, a robust adaptive controller is proposed via backstepping method, in which adaptive law is synthesized to deal with parametric uncertainties and a continuous nonlinear robust control law to suppress unmodeled disturbances. Since the unknown dead-zone parameters can be estimated by adaptive law and then the effect of dead-zone can be compensated effectively via inverse operation, improved tracking performance can be expected. In addition, the disturbance upper bounds can also be updated online by adaptive laws, which increases the controller operability in practice. The Lyapunov based stability analysis shows that excellent asymptotic output tracking with zero steady-state error can be achieved by the developed controller even in the presence of unmodeled disturbance and unknown valve dead-zone. Finally, the proposed control strategy is experimentally tested on a servovalve controlled hydraulic actuation system subjected to an artificial valve dead-zone. Comparative experimental results are obtained to illustrate the effectiveness of the proposed control scheme.     

Robust adaptive motion/force control scheme for crawler-type mobile manipulator with nonholonomic constraint based on sliding mode control approach

In this paper, a robust adaptive motion/force control (RAMFC) scheme is presented for a crawler-type mobile manipulator (CTMM) with nonholonomic constraint. For the position tracking control design, an adaptive sliding mode tracking controller is proposed to deal with the unknown upper bounds of system parameter uncertainties and external disturbances. Based on the position tracking results, a robust control strategy is also developed for the nonholonomic constraint force of CTMM. According to the Lyapunov stability theory, the stability of the closed-loop control system, the uniformly ultimately boundedness of position tracking errors, and the boundedness of the force error and adaptive coefficient errors are all guaranteed by using the derived RAMFC scheme. Simulation and experimental tests on a CTMM with two-link manipulator demonstrate the effectiveness and robustness of the proposed control scheme.     

大型移动机械设备的运行控制

根据大型移动机械设备运行的实际情况,综合应用了传感器技术、模糊控制技术、无线通信技术和计算机技术,实现了大型移动机械设备的操作实时监控、信号连锁、运动控制和生产计划的自动调度、管理.     

A large deflection and high payload flexure-based parallel manipulator for UV nanoimprint lithography: Part I. Modeling and analyses

This paper presents a flexure-based parallel manipulator (FPM) that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nanoimprint lithography (UV-NIL) process. The FPM is articulated from a novel 3-legged prismatic-prismatic-spherical (3PPS) parallel-kinematic configuration to deliver a θ_x–θ_y–Z motion. The developed FPM achieves a positioning and orientation resolution of ±10 nm and 0 . 05″ respectively, and a continuous output force of 150 N/Amp throughout a large workspace of 5°×5°×5 mm. Part I mainly focuses on a new theoretical model that is used to analyze the stiffness characteristics of the compliant joint modules that formed the FPM, and experimental evaluations of each compliant joint module. Part II presents the stiffness modeling of the FPM, the performance evaluations of the developed prototype, and the preliminary results of the UV-NIL process.     

Precision design and control of a flexure-based roll-to-roll printing system

This paper presents the design, characterization, and control of a flexure-based roll-to-roll (R2R) printing system that achieves nanometer level precision and repeatability. The R2R system includes an unwinding/rewinding module, a web guide mechanism, and a core positioning stage consisting of two monolithic compliant X–Y stages that control the position/force of the print roller. During the printing process, capacitance probes, eddy current sensors and load cells are used to monitor the displacements of the flexure stage and contact force in real time. Control strategies, including decoupling, PID, and cascade control, have been implemented to decouple the cross-axis and cross-stage motion coupling effect and improve the overall precision and dynamic performance. In actual printing processes, the contact force and roller position can be uniformly controlled within ±0.05 N and ±200 nm respectively across a 4 in. wide PET web. To demonstrate the performance, a positive microcontact printing (MCP) process is adapted to the R2R system, printing various fine metal patterns, e.g., optical gratings and electrodes, in a continuous fashion.     

Robust motion control of a clamp-cylinder for energy-saving injection moulding machines

This paper deals with the issue of robust motion control of a clamp-cylinder for injection moulding machines driven by a pair of speed-controlled fixed displacement pumps. As a fundamental step prior to tracking controller design, a feedback control system is suggested by implementing a position control loop in parallel with a system pressure control loop. A discrete-time sliding mode control scheme is developed for enhancing the tracking performance under inherent nonlinearities. Consequently, a significant reduction in tracking error is achieved for both position and pressure control applications. This paper was recommended for publication in revised form by Associate Editor Dong Hwan Kim Seung Ho Cho received his B.S., M.S., and Ph.D. degrees from Seoul National University in 1978, 1981, and 1986, respectively. He then went on to perform his Post-Doc. research from U.C. Berkeley in 1989–1990. Dr. Cho is currently a Professor at the Mechanical and System Design Engineering of Hongik University in Seoul, Korea. Dr. Cho’s research interests are in the area of automatic control applications, fluid power control, and energy-saving drive systems.     

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.     

压电作动器存在故障时柔性板的鲁棒振动控制研究

首先识别出黏贴压电作动器的柔性板振动控制系统的实验模型,接着提出了利用改变压电片对连接数量来模拟作动器驱动故障的方法。基于此,将驱动力变化带来的模型不确定性提取成正则不确定块对角阵,将剩余模态表示成高通滤波器,并引入虚拟不确定矩阵,从而构建出考虑外扰抑制和控制增益约束的μ综合控制器。实测结果表明,相对于一般的μ综合控制器,当出现压电片连接故障时,闭环系统在初始外扰下的对数衰减率增大了3倍。     

空间机械臂姿态及关节运动的自适应与鲁棒控制

讨论了载体位置不受控制的漂浮基空间机械臂系统的控制问题。借助于增广变量法,恰当地扩展系统的控制输入与输出,克服了漂浮基空间机械臂系统控制方程关于惯性参数呈非线性函数关系的难点,保持了系统控制方程关于惯性参数的线性函数关系。以此为基础,针对末端抓手持有载荷参数未知与不确定两种情况,设计了载体姿态与机械臂关节协调运动的自适应控制与鲁棒控制两种方案。仿真运算证实了上述控制方案的有效性。     

基于多摄像机的鲁棒运动结构重建方法

考虑大尺度噪声对测量矩阵的影响,提出了一种基于多摄像机的鲁棒运动结构重建方法.通过引入一种用于低秩矩阵恢复的数学模型,将丢失数据和大尺度噪声造成的不完整测量矩阵求解转化为凸优化问题,并使用鲁棒主成分分析方法对其求解,利用多摄像机下的矩阵分解理论实现多摄像机下运动结构重建.实验结果表明,提出的方法能够有效解决大尺度噪声的存在造成多摄像机运动结构重建方法失效的问题,准确地重建物体三维结构.