磁驱动微型机器人的智能控制发展现状

低强度磁场无线驱动的微型机器人可以在狭小空间中运动并完成复杂作业任务,如靶向给药、微操作及环境检测等。本文旨在总结磁驱动微型机器人的智能控制发展现状,主要包括智能控制方法在以下方面的应用：从刚性结构到柔性结构的磁驱动微型机器人,从单一运动模态到多种运动模态的磁驱动微型机器人,从开环控制到闭环控制的磁驱动微型机器人,从单个个体到单个群体再到多个个体的磁驱动微型机器人。最后,展望了磁驱动微型机器人的未来发展方向,包括更大空间的磁驱动装置,更多运动模态的微型机器人,软体结构的医疗微型机器人,微型机器人自主导航和多个磁驱动微型机器人的控制。     

基于有限元方法的3-PPSR大长径比柔性并联机器人刚度模型分析

为实现较大工作空间的运动,设计了一种大长径比的3-PPSR结构的微操作柔性并联机器人.该机器人由压电马达驱动,采用大长径比柔性铰链连接,柔性铰链的变形范围在毫米级,适用于要求大变形的场合,同时具有结构简单、无奇异、无间隙、运动精度高等特点.由于系统的刚度直接影响系统的运动精度、承载负荷等性能,针对大长径比柔性铰链特点,运用有限元方法,建立了柔性铰链的数学模型,并采用整体刚度的方法,结合机构协调方程和力平衡方程,得到系统的柔性刚度模型.最后,采用ANSYS比较了所建理论刚度模型结果与有限元模型分析的结果.分析结果表明,理论刚度模型合理,符合机构的运动特征.     

一种基于空间连杆机构的蛇形机器人

提出了一种基于空间连杆机构的蛇形机器人模型．该蛇形机器人各骨节间通过万向铰链连接,每节安装两个微型伺服电机,电机带动曲柄转动,曲柄经两端为球铰的连杆驱动另一骨节运动．通过两个电机的耦合驱动,该蛇形机器人能实现蜿蜒爬行、转向、抬头等多种运动方式．文中给出了该空间连杆机构的运动学解,基于Serpenoid曲线计算得到了实际控制所需的关节转角和步数,并编程实现了上述运动方式．     

全柔性机器人机构的结构构型研究

本文对全柔性机器人机构的结构构型问题进行了系统的讨论：首先从应用层面上对 全柔性机器人机构进行了分类，着重讨论了并联机构与全柔性机器人机构之间存在的有机联 系．通过对并联机构的结构及柔性铰链的几何模型进行系统的总结，为全柔性机器人机构“ 型”的选择与构筑提供了丰富的素材．此外，还重点讨论了对全柔性机器人机构的性能产生 较为显著影响的结构布局问题．     

连续型机器人运动学仿真和操控系统设计

为了适应越来越复杂的非结构化环境,设计了一种基于球铰链连接和柔性支撑杆结合的线驱动连续型机械臂,并基于常曲率模型的假设建立连续型机器人的运动学模型,研究连续型机器人驱动映射关系,利用MATLAB进行运动学和驱动映射的仿真,仿真结果表明连续型机器人的空间优越性。搭建三关节连续型机器人样机平台,基于连续型机器人的特点设计末端关节跟随手柄操作模式,并在样机平台上实验验证,实验结果表明了运动学模型和驱动映射关系的合理性和正确性以及操控方式的可行性。     

微型仿生肠道内窥镜机器人的设计与实验

根据当前胃肠道内窥镜自主运动机器人的研究方向,设计了一种微型的肠道内窥镜机器人系统。机器人采用仿尺蠖式的运动步态,通过直流无刷电机驱动驻留-伸缩-驻留式的结构实现主动运动。整体采用模块化设计,主要包括驻留机构、伸缩机构、电路控制系统以及无线供能模块。对机器人结构模型进行了理论探讨,介绍了电路控制系统的设计,以及无线供能模块的构成。最终的机器人样机直径约为14 mm,整体长度约为61 mm。机器人在PVC柔性管道和猪小肠离体爬行实验中运行稳定可靠,能够实现前进、退后和停留等步态。实验结果表明该微型仿生肠道内窥镜机器人在肠道内可以实现主动运动。     

基于柔性铰链支承的热驱动硅微机械手的力学模型及性能分析

微机械手是一种典型的微型执行器,是微型机电系统(MEMS)的重要研究内容之一.以基于柔性铰链的电热驱动硅微机械手为研究对象,建立了微夹钳的二次超静定力学模型,导出了钳口处输出位移的解析式,并在此基础上对硅微机械手的性能进行了分析.分析表明,微夹钳的输出位移与柔性铰链切割半径成正比,切割半径越大,输出位移越大;对各加载电压下的微夹钳输出位移,其试验和理论结果的变化趋势一致,即微夹钳输出位移随输入电压的增加基本呈线性增加.     

并联微机器人的逆动力学

本文基于牛顿 欧拉法建立了一类PSS副、带柔性铰链的六自由度并联微机器人的 逆动力学方程,这是设计、控制微机器人的前提和基础．所建模型不仅考虑了因柔性铰链的 特殊性,微机器人连杆绕自身轴线转动的内部运动,还分析了柔性球铰弹性变形产生的反力 矩．由于微机器人机构本体以及逆动力学建模过程中所固有的并联特性,对逆动力学可实施 并行算法．最后以一实例进行了仿真分析,仿真结果表明微机器人所需驱动力呈线性变化, 揭示了微机器人在微动情况下的线性本质．     

外磁场驱动医用微型机器人的研究现状与展望

介绍了国内外关于外磁场驱动控制微型机器人的最新研究成果,并对其作业机理进行了分析. 分析表明外磁场无缆驱动控制方法是提高体内医疗微型机器人实用性的有效途径和技术关键．结合我们开发研制的外场驱动微型游动机器人的实际情况,指出了目前无缆外磁场驱动微型机器人存在的问题,并对体内游动型微型医疗机器人实用化的关键技术和发展趋势进行了探讨．     

主被动关节柔性树形机器人系统动力学建模与仿真

进一步完善空间算子代数理论体系,研究了带有主被动关节的树形柔性机器人系统符号动力学高效率建模的方法.利用拓扑结构和低序体阵列的方法描述了树型机器人系统.采用空间算子研究了欠驱动树型多体系统的描述方法.根据系统中铰的驱动情况分别对铰链定义为主动铰和被动铰,建立树形机器人系统的运动学,然后通过铰链的类型分别按照两次从系统的顶端到基座的顺序、一次从基座到顶端的顺序进行了系统铰接体惯量的递推、系统冗余力的递推、广义加速度和广义主动力的递推,最后将分叉处的广义力和广义加速度矢量相加得到树形机器人系统的广义动力学模型.通过上述递推过程建立动力学模型,实现了高效率O(N)(N为系统自由度)次的计算效率.最后以加拿大树形空间机械臂为例做仿真验证了本研究内容的正确性和高效性.     

基于柔性铰链的热驱动微夹钳的实验和仿真分析

微执行器在整个微机电系统中直接面对其应用对象,需要满足定位精度高,稳定性好,响应速度快,控制方便的要求.柔性铰链以其特殊的性能广泛应用于操作执行器的设计应用中.以一种基于柔性铰链的电热驱动微夹钳为研究对象,通过实验和ANSYS有限元仿真分析对微夹钳的机械性能进行了分析,发现微夹钳端部的输出位移与输入电压基本呈线形关系.通过仿真分析探讨了柔性铰链结构尺寸变化对微夹钳性能的的影响.     

Study of the hinge thickness deviation for a 316L parallelogram flexure mechanism fabricated via selective laser melting

3D printing offers great potential for developing complex flexure mechanisms. Recently, thickness-correction factors (TCFs) were introduced to correct the thickness and stiffness deviations of powder-based metal 3D printed flexure hinges during design and analysis. However, the reasons for the different TCFs obtained in each study are not clear, resulting in a limited value of these TCFs for future design and fabrication. Herein, the influence of the porous layer of 3D printed flexure hinges on the hinge thickness is investigated. Samples of parallelogram flexure mechanisms (PFMs) were 3D printed using selective laser melting (SLM) and 316L stainless steel powder. A 3D manufacturing error analysis was completed for each PFM sample via 3D scanning, surface roughness measurement and morphological observation. The thickness of the porous layer of the flexure hinge was independent of the designed hinge thickness and remained close to the average powder particle diameter. The effective hinge thickness could be estimated by subtracting twice the value of the porous layer thickness from the designed value. Guidelines based on finite element analysis and stiffness experiments are proposed. The limitations of the presented method for evaluating the effective hinge thickness of flexure hinges 3D printed via SLM are also discussed.

     

Design of an auto-focusing actuator with a flexure-based compliant mechanism for mobile imaging devices

There is increasing consumer’s demand for high-quality and high-performance mobile imaging devices. In this paper, an auto-focusing (AF) actuator with a flexure hinge that uses the electromagnetic (EM) circuit of a voice coil motor was designed and evaluated. The flexure hinge was designed by using finite element analysis. The EM circuit was designed based on the structural stiffness of the device. The EM circuit was analyzed using the design of experiments procedure. Based on the results, the effective design parameters were selected, and improvements were made to the design. Finally, a prototype of the AF actuator was manufactured, and the feasibility and performance of the actuator with the flexure hinge were verified experimentally. The experimental results indicated that the proposed actuator performed adequately and satisfied the design requirements.     

Two-axis flexure hinges with axially-collocated and symmetric notches

The paper introduces a new class of two-axis flexure hinges with axially-collocated and symmetric notches as an alternative to the existing flexure designs with serially-disposed notches. A generic formulation is developed in terms of the geometric curves defining the two notches which includes assessing the capacity of rotation, precision of rotation, sensitivity to parasitic effects, stress values, motion efficiency and shearing effects by means of compliance factors. Closed-form compliance equations are derived for a two-axis flexure hinge that is defined by two non-identical parabolic profiles. The analytical model predictions are confirmed by finite element data. A numerical comparison is made of the parabolic flexure with a constant rectangular cross-section flexure hinge in terms of several performance criteria.     

Design and performance evaluation of a novel stick–slip piezoelectric linear actuator with a centrosymmetric-type flexure hinge mechanism

Microsystem Technologies - A stick–slip actuator with a centrosymmetric type flexure hinge mechanism was presented in this paper. The dimension of the actuator is approximately...     

Kinematic analysis of a translational 3-d.o.f. micro-parallel mechanism using the matrix method

In this paper, we applied the matrix method to kinematic analysis of our translational 3-d.o.f. micro-parallel mechanism for an instance of general flexure mechanisms. The matrix method has been well developed in architecture to analyze frame structures. We found that this method is well suited to such a flexure mechanism with circular notched hinges as our micro-parallel mechanism because it can be approximated to a Rahmen structure. Our matrix method can calculate a compliance matrix with less matrix nodes than the conventional finite element method. First, the compliance matrices of a circular notched hinge and some other beams are defined, and the coordinate transformations of the compliance matrix are introduced. Secondly, an analysis of our micro-parallel mechanism is demonstrated.     

A parasitic type piezoelectric actuator with an asymmetrical flexure hinge mechanism

A parasitic type actuator with an asymmetrical flexure hinge mechanism has been proposed in this study to achieve linear motion with a large working stroke. The principal output direction of the piezoelectric stack is vertical to the motion direction of the mover to obtain a large output load. The composition of the parasitic type actuator and working process are introduced and parasitic motion is explained. Finite element method has been applied to analyze the parasitic motion of the proposed asymmetrical flexure hinge mechanism. Moreover, an experiment system of the parasitic type actuator is set up, and experiments show that the positioning resolution of the actuator is around 0.1 μm; the maximum motion speed could achieve to 2850 μm/s when the input frequency f = 500 Hz and the input voltage U_e = 100 V; the maximum output force F_g is up to 750 g when the input frequency f = 1 Hz and the input voltage U_e = 100 V. This study indicates that the asymmetrical flexure hinge mechanism could achieve parasitic motion for the design and application of piezoelectric actuators with a large working stroke.

     

Optimal displacement amplification ratio of bridge-type compliant mechanism flexure hinge using the Taguchi method with grey relational analysis

Microsystem Technologies - The compliant mechanism flexure hinge has been frequently utilized in precision enginering in recent years, such as the bridge-type and rhombus-type compliant mechanisms....     

On using flexure‐hinge five‐bar linkages to develop novel walking mechanisms and small‐scale grippers for microrobots

This paper presents the micromotion analysis of five‐bar linkages and demonstrates the approximate linearity of motion transmission of five‐bar mechanisms within a micromotion range. A novel walking mechanism used for a microrobot and a small‐scale gripper with a high transmission ratio are introduced, based on the flexure‐hinge five‐bar mechanism analysis. Results of numerical simulation show the validity of design and analysis on the introduced mechanisms and the feasibility of corresponding thoughts. The presented micromotion‐based robot mechanisms are devoid of friction and fitting errors, and particularly suitable for microrobot applications. © 2004 Wiley Periodicals, Inc.     

Analytical model of displacement amplification and stiffness optimization for a class of flexure-based compliant mechanisms

The paper formulates an analytical method for displacement and stiffness calculations of planar compliant mechanisms with single-axis flexure hinges. The procedure is based on the strain energy and Castigliano’s displacement theorem and produces closed-form equations that incorporate the compliances characterizing any analytically-defined hinge, together with the other geometric and material properties of the compliant mechanism. Displacement amplification, input stiffness and output stiffness calculations can simply be performed for any serial compliant mechanism. The class of amplifying compliant mechanisms that contain symmetric corner-filleted or circular flexure hinges is specifically addressed here. A parametric study of the mechanism performance is performed, based on the mathematical model, and an optimization procedure is proposed, based on Lagrange’s multipliers and Kuhn-Tucker conditions, which identifies the design vector that maximizes the performance of these flexure-based compliant mechanisms. Independent finite element simulation confirms the analytical model predictions.