A simple PID control for asymptotic visual regulation of robot manipulators

This paper addresses the asymptotic regulation problem of robot manipulators with a vision‐based feedback. A simple image‐based transpose Jacobian proportional‐integral‐derivative (PID) control is proposed. The closed‐loop system formed by the proposed PID control and robot system is shown to be asymptotically stable by using Lyapunov's direct method and LaSalle's invariance theorem. Advantages of the proposed control include the absence of dynamical model parameters in the control law formulation and the control gains are easily chosen according to simple inequalities including some well‐known bounds extracted from robot dynamics and kinematics. Simulations performed on a two degree‐of‐freedom manipulator are provided to illustrate the effectiveness of the proposed approach. Copyright © 2010 John Wiley & Sons, Ltd.     

Visual Homing: Surfing on the Epipoles

We introduce a novel method for visual homing. Using this method a robot can be sent to desired positions and orientations in 3D space specified by single images taken from these positions. Our method is based on recovering the epipolar geometry relating the current image taken by the robot and the target image. Using the epipolar geometry, most of the parameters which specify the differences in position and orientation of the camera between the two images are recovered. However, since not all of the parameters can be recovered from two images, we have developed specific methods to bypass these missing parameters and resolve the ambiguities that exist. We present two homing algorithms for two standard projection models, weak and full perspective.Our method determines the path of the robot on-line, the starting position of the robot is relatively not constrained, and a 3D model of the environment is not required. The method is almost entirely memoryless, in the sense that at every step the path to the target position is determined independently of the previous path taken by the robot. Because of this property the robot may be able, while moving toward the target, to perform auxiliary tasks or to avoid obstacles, without this impairing its ability to eventually reach the target position. We have performed simulations and real experiments which demonstrate the robustness of the method and that the algorithms always converge to the target pose.     

Dynamic analysis and intelligent control techniques for flexible manipulators: a review

This paper reviews literature on dynamic analysis and intelligent control techniques for flexible robot manipulators. First, a comparative dynamic analysis of flexible manipulators was presented and then control strategies were categorized and studied. Fuzzy logic, neural network, and genetic algorithm approaches were introduced and a range of contributions of such methods in flexible robot control were presented. A total of 115 papers were surveyed in this research, covering a sufficient depth in assessment of dynamic and control of flexible manipulator systems for the time span of 1970–2013.     

基于图像视觉伺服的二维运动优化控制

基于图像的视觉伺服方法,图像的变化直接解释为摄像机的运动,而不是直接对机械手末端实现笛卡尔速度控制,导致机械手的运动轨迹迂回,产生摄像机回退现象.针对这一问题,提出了将旋转和平移分离并先实现旋转的视觉伺服方案.该方案计算量小,系统响应时间短,解决了图像旋转和平移间的干扰,克服了传统基于图像视觉伺服产生的摄像机回退现象,实现了时间和路径的最优控制.并用传统IBVS的控制律和摄像机成像模型解释了回退现象的产生原因.二维运动仿真说明了提出方案的有效性.     

柔性机械臂的双时间尺度组合控制

本文研究柔性机械臂的轨迹跟踪和振动抑制问题. 首先, 利用Lagrange法和假设模态法建立柔性机械臂的动态模型, 进而利用奇异摄动理论得到柔性机械臂的双时间尺度模型. 然后, 基于慢时间尺度模型利用滑模控制理论设计轨迹跟踪控制器; 借助于快时间尺度模型利用自适应动态规划设计参数不精确已知情况下的最优振动抑制控制器; 将二者相结合, 构造双时间尺度组合控制器, 利用奇异摄动理论证明闭环系统稳定. 最后, 在Matlab/Simulink环境下进行实验, 与现有方法相比, 本文设计的控制器对柔性振动具有更好的振动抑制效果, 跟踪精度更高.     

基于视觉的服务机器人轨迹跟踪控制

根据移动服务机器人的运动学模型和针孔摄像机成像原理,完成了机器人的速度向量由视觉空间到任务空间的变换。采用视觉伺服控制方式,结合反步设计思想,设计了具有全局渐近稳定的轨迹跟踪控制器,并利用Lyapunov函数进行稳定性分析。仿真结果验证了所设计控制器的有效性和正确性。     

双臂柔性机械手的终端滑模控制

提出一种用于双臂柔性机械手系统的终端滑模控制方法，以解决其非最小相位控制问题．重新定义了柔性机械手系统的输出，通过输入输出线性化，将系统分解为输入输出子系统和内部子系统．设计逆动态终端滑模控制策略，使输入输出子系统在有限时间内收敛到零；选择适当的控制器参数，使零动态子系统在平衡点附近渐近稳定，从而保证整个系统的渐近稳定．仿真结果证明了该设计方法的有效性．     

A review on two-link flexible manipulators

This paper presents a survey in the field of two-link flexible manipulators (TLFMs). Two-link flexible manipulators are more used in comparison with other types of flexible manipulators. Therefore, this paper discusses various aspects of the reported works of TLFMs available in the literature. The papers based on TLFMs are classified into modeling methods, dynamical analyses, complexities involved and control schemes used. The modeling methods discuss the various types of modeling used for a TLFM. A brief note on the complexities involved in the flexible manipulators are presented. The main categories of the control problems addressed by the available papers are also discussed. The classification of the control techniques is made according to the nature of controllers. It is also mentioned in the paper as to whether the reported work deals with only simulation based results or are validated with the experimental work.     

机器人视觉伺服研究进展

介绍了机器人视觉伺服系统的结构和主要研究内容,比较了当前几种主要的视觉伺服方法,针对当前 机器人视觉伺服所面临的主要问题,详细阐述了近期提出的一些解决方法.     

Mutational equations for shapes and vision-based control

Basic idea of vision-based control in robotics is to include the vision system directly in the control servo loop of the robot. When images are binary, this problem corresponds to the control of the evolution of a geometric domain. The present paper proposes mathematical tools derived from shape analysis and optimization to study this problem in a quite general way, i.e., without any regularity assumptions or modelsa priori on the domains that we deal with. Indeed, despite the lackness of a vectorial structure, one can develop a differential calculus in the metric space of all non-empty compact subsets of a given domain ofR ⁿ , and adapt ideas and results of classical differential systems to study and control the evolution of geometric domains. For instance, a shape Lyapunov characterization allows to investigate the asymptotic behavior of these geometric domains using the notion of directional shape derivative. We apply this inR ² to the visual servoing problem using the optical flow equations and some experimental simulations illustrate this approach.     

Motion control of dual-arm long-reach manipulators

This work reports progress on a long-reach manipulator project. The original single-arm manipulator was complemented with an identical second arm. We introduce several non-contact motion control strategies which are based on the reaction null space concept developed earlier. Experimental verification of disturbance compensation control via a single arm, and via the two arms while holding an object, is done. Also, motion feasibility on reactionless paths for a closed kinematic chain, including the two arms and the object, is examined.     

参数不确定柔性机械手的终端滑模控制

针对参数不确定双臂柔性机械手系统, 提出一种基于遗传算法的终端滑模控制方法, 以实现其末端控制.基于输出重定义方法, 通过输入输出线性化, 将系统分解为输入输出子系统和内部子系统. 设计终端滑模控制策略,使输入输出子系统有限时间内收敛到零, 内部子系统变为零动态子系统; 采用遗传算法优化零动态子系统参数, 使其在平衡点附近渐近稳定. 根据Lyapunov稳定性理论算出末端输出位移的误差范围. 仿真结果证明该方法有效性.     

A flexible capacitive tactile sensor array with micro structure for robotic application

A flexible capacitive tactile sensor array with micro needle structure is proposed in this paper for robotic application. Micro needle layer made of polydimethylsiloxane （PDMS） is sandwiched between the upper electrode layer made of PDMS and the bottom electrode layer fabricated on polyester （PET） film. The PDMS material renders the device adequate flexibility as it can be rolled into a cylinder. The single cell size in the fabricated 4 ~ 4 sensors array is 0.7 ~ 0.5 cm2 and the initial capacitance of each cell is 0.86 pF. The fabricated cell shows a sensitivity of 3.26%/mN within the full scale range of I kPa. The micro needle structure gives better repeatability and stability. The maximum error during each measurement is about 3.2%, while the minimum error is about 1.2%.     

Dynamic modelling and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances

In this paper, both the closed-form dynamics and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances are developed. The dynamic model of the system is described with assumed modes approach and Lagrangian method. The flexible manipulators are represented as Euler–Bernoulli beams. Based on singular perturbation technique, the displacements/joint angles and flexible modes are modelled as slow and fast variables, respectively. A sliding mode control is designed for trajectories tracking of the slow subsystem under unknown but bounded disturbances, and an adaptive sliding mode control is derived for slow subsystem under unknown slowly time-varying disturbances. An optimal linear quadratic regulator method is proposed for the fast subsystem to damp out the vibrations of the flexible manipulators. Theoretical analysis validates the stability of the proposed composite controller. Numerical simulation results demonstrate the performance of the closed-loop flexible space robot system.     

A timing model for vision-based control of industrial robot manipulators

Visual sensing for robotics has been around for decades, but our understanding of a timing model remains crude. By timing model, we refer to the delays (processing lag and motion lag) between "reality" (when a part is sensed), through data processing (the processing of image data to determine part position and orientation), through control (the computation and initiation of robot motion), through "arrival" (when the robot reaches the commanded goal). In this study, we introduce a timing model where sensing and control operate asynchronously. We apply this model to a robotic workcell consisting of a Sta/spl uml/ubli RX-130 industrial robot manipulator, a network of six cameras for sensing, and an off-the-shelf Adept MV-19 controller. We present experiments to demonstrate how the model can be applied.     

基于Adept机器人的视觉伺服控制系统

机器人视觉伺服控制在理论和应用等方面还有许多问题需要研究,例如特征选择、系统标定和伺服控制算法等.针对Adept机器人,提出了一种简单快速的不需要精确标定摄像机内外部参数的摄像机标定方法,完成了从被观测物体表面所在的视觉平面坐标系到机器人基坐标系的坐标变换.使用图像的全局特征,即图像矩特征进行伺服跟踪;利用所推导的图像雅可比矩阵,设计了由图像反馈与目标运动自适应补偿组成的视觉伺服控制器.将算法对静态目标的定位实验进行了验证,然后又将其应用到移动目标的跟踪上,通过调节和优选控制参数,实现了稳定的伺服跟踪和抓取.实验结果表明采用图像矩作为图像特征能够避免复杂的特征匹配过程,并且能够获得较好的跟踪精度.     

A hybrid frequency—time domain adaptive fuzzy control scheme for flexible link manipulators

This paper addresses the implementation of an adaptive fuzzy controller for flexible link robot arms. The design technique is a hybrid scheme involving both frequency and time domain techniques. The eigenvalues of the open loop plant can be estimated through application of a frequency domain based identification algorithm. The region of the eigenvalue space, within which the system operates, is partitioned into fuzzy cells. Membership function are assigned to the fuzzy sets of the eigenvalue universe of discourse. The degree of uncertainty on the estimated eigenvalues is encountered through these membership functions. The knowledge data base consists of feedback gains required to place the closed loop poles at predefined locations. A rule based controller infers the control input variable weighting each with the value of the membership functions at the identified eigenvalue. The afore-mentioned controller is compared through simulation with conventional techniques, namely pole placement and gain scheduling.     

机器人视觉伺服系统的研究

机器人伺觉伺服系统及到多学科内容。针对机器人视觉伺服系统主要的三方面内容;系统的结构方式,图象处理,控制方法,介绍了该领域的研究现状及所取得的成就。最后分析了今后的发展趋势。     

3-D positioning control by linear visual servoing

This article describes the performance of 3-D positioning control by linear visual servoing using binocular visual space in a human-like hand-eye system which has a similar kinetic structure to a human being. We approximate the nonlinear time-variant mapping from a binocular visual space to the joint space of the manipulator as a linear time-invariant mapping. We also investigate the effect of binocular visual space in linear mapping by comparing it with linear mapping using Cartesian space. Some experimental results are presented using the human-like hand-eye system to demonstrate the performance of 3-D positioning control. This work was presented, in part, at the Seventh International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002