基于压电陶瓷驱动的并联微动机器人应用现状

介绍了具有刚度大、承载能力强、位置误差不积累等特点的并联微动机器人,在应用上与串联机器人呈互补关系,已经成为微动机器人领域的研究热点。随着科学技术的发展,许多领域越来越迫切地需要微型系统或微动系统。目前,并联微动机器人已经在航天、航空、制造业、计算机辅助医疗设备、生物工程以及微机电系统等方面有着广泛而重要的应用。     

压电驱动三支链六自由度微动机器人机构设计

为简化6支链并联微动机器人结构、减小其装配误差,提出了压电陶瓷驱动的3支链6自由度并联微动机器人结构。采用整体式下平台和3条两端带有柔性球铰链和单轴直圆柔性铰链的支杆,使结构紧凑并有利于提高精度。在分析逆解的基础上,根据工作空间要求设计了整体尺寸。根据柔性铰链选取原则,对直角平板和支杆处柔性铰链进行尺寸选择,采用有限元分析对整体刚度进行分析和安全校验。样机测试结果表明了设计的可行性。     

3-RPR平面并联机器人工作空间研究

对平面3自由度3-RPR并联机器人的工作空间的求解方法与性质进行了探讨。分析了3-RPR并联机器人工作空间的影响因素,以支腿长度约束、支腿与动平台交汇条件以及支腿与动平台夹角限制为约束条件,并采用快速极坐标搜索法确定了3-RPR并联机器人的工作空间。研究了构型参数与工作空间的关系。     

六自由度压电驱动并联微动机构设计与分析

采用理论分析、有限元分析与仿真方法相结合的方法,设计并分析了一套新型的压电陶瓷驱动的六自由度并联微动机器人机构,充分发挥压电陶瓷和并联机构的优点,实现了并联机器人机构、驱动、检测-体化设计。经过实际检测证明,所采取的方案是合理可行的。     

Par4并联机器人轨迹规划研究

研究了Par4并联机器人操作空间的轨迹规划算法。分析了Par4并联机器人机械结构,采用几何分析法得出其运动学模型。采用了SCCA凸轮运动模式进行速度规划。在操作空间中将直线插补和圆弧插补运用于并联机器人末端轨迹规划。将两种插补规划运用于Par4并联机器人,并在MATLAB2010a中进行仿真分析,验证了两种轨迹规划应用于Par4并联机器人的可行性和合理性,为机器人的运动控制控制提供理论基础。     

机器人、机械手、自动调节、控制与执行机构

0625143服务机器人多通道人机交互感知反馈工作机制及关键技术=Information perception and feedback mechanism and key techniques of multi-modality human-robot inter- action for service robots[刊,英]/赵其杰//上海大学学报(英文版)．—2006,10(3)．—281(E) 0625144可重构星球探测机器人跨越壕沟能力研究=Crossing ditch for reconfigurable planetary robocs[刊,英]/张力平//上海大学学报(英文版)．—2006,10(3)．—256-261 (E) 0625145一种2自由度平面并联机器人的精度分析[刊,中]/李贯成//南昌大学学报(工科版)．—2006,28(2)．—130- 133(G)以一种2自由度平面并联机器人机构为对象,分析了该并联机器人机构的误差源,首先利用图解法得到该平面并联机器人机构的可达工作空间和有效工作空间,再利用环路增量法和误差分离技术导出了末端位置误差与误差源之间的映射关系,因而为其在工作空间内的位姿误差建立了数学模型,给出了这个平面并联机器人机构位姿误差的计算方法,从而对其进行精度分析,最后借助于搜索法得到了其在有效工作空间内的误差分布图像。参6     

5-DOF并串联机器人运动学分析及仿真

并联机器人强度刚度较高,但是工作空间较小;串联机器人工作空间较大,但强度刚度较小。混联机构因兼顾了并联和串联机构的优点而具有更加广泛的应用前景。文中介绍了一种新型五自由度并串联机器人来实现复杂曲面的加工。应用螺旋理论对其运动性质进行分析并计算了自由度。通过数值法推导了机器人的正解,运用解析法推导了机器人的反解。用SolidWorks构建了机器人的三维模型并导入到ADAMS中对其进行运动学仿真。仿真结果显示,该机器人能够实现复杂曲面的加工,可以为工业生产提供帮助。     

新型副镜并联调整机构非线性特性及校正

为满足望远镜副镜结构定位精度的要求,提出一种固定杆长杆端轴向平移运动模式的六杆并联机构。从微分几何的观点研究了该机构输入关节空间向量与输出工作空间向量之间的非线性运动学特性,并采用曲率概念度量解轨迹的非线性弯曲。通过与雅可比矩阵的对比分析可知,采用曲率度量并联机构的非线性和采用雅克比矩阵反映的瞬时线性性质一致,所设计的副镜并联调整机构在整个运动行程范围内的最大非线性误差约为3.15 μm。测试结果表明:采用多项式误差曲线拟合校正之后,该副镜调整机构三维平移重复定位精度小于2.6 μm,二维旋转重复定位精度小于1.8″,满足实际望远镜观测的需要,采用的曲率度量法也可以为其他并联机构的非线性分析和校正提供一种新的思路。     

容错技术在并联机器人控制系统中的应用

本文即是对容错技术在并联机器人控制系统中的应用进行研究,探讨了容错技术的概念,并对并联机器人的各种控制方法进行探讨,最后就容错技术在6-DOF型并联机器人控制系统中的应用进行研究,以期能为相关工作提供参考。     

压电陶瓷驱动并联微动机器人位姿测量与误差补偿

设计了一套针对六自由度微动并联机器人的位姿测量机构,并在压电陶瓷的开环与闭环控制状态下进行了位姿测量。实验证明,通过对压电陶瓷的闭环控制可消除压电陶瓷的迟滞与蠕变,系统定位误差明显减小,使用微位移循环修正法深入进行误差分析,确定初始误差,在此基础上,提出了误差补偿的方法,并验证了其可行性．     

Admittance controller complemented with real-time singularity avoidance for rehabilitation parallel robots

Rehabilitation tasks demand robust and accurate trajectory-tracking performance, mainly achieved with parallel robots. In this field, limiting the value of the force exerted on the patient is crucial, especially when an injured limb is involved. In human–robot interaction studies, the admittance controller modifies the location of the robot according to the user efforts driving the end-effector to an arbitrary location within the workspace. However, a parallel robot has singularities within the workspace, making implementing a conventional admittance controller unsafe. Thus, this study proposes an admittance controller that overcomes the limitations of singular configurations by using a real-time singularity avoidance algorithm. The singularity avoidance algorithm modifies the original trajectory based on the actual location of the parallel robot. The complemented admittance controller is applied to a 4 degrees of freedom parallel robot for knee rehabilitation. In this case, the actual location is measured by a 3D tracking system because the location calculated by the forward kinematics is inaccurate in the vicinity of a singularity. The experimental results verify the effectiveness of the proposed admittance controller for safe knee rehabilitation exercises.     

Design and Development of a Medical Parallel Robot for Cardiopulmonary Resuscitation

The concept of a medical parallel robot applicable to chest compression in the process of cardiopulmonary resuscitation (CPR) is proposed in this paper. According to the requirement of CPR action, a three-prismatic-universal-universal (3-PUU) translational parallel manipulator (TPM) is designed and developed for such applications, and a detailed analysis has been performed for the 3-PUU TPM involving the issues of kinematics, dynamics, and control. In view of the physical constraints imposed by mechanical joints, both the robot-reachable workspace and the maximum inscribed cylinder-usable workspace are determined. Moreover, the singularity analysis is carried out via the screw theory, and the robot architecture is optimized to obtain a large well-conditioning usable workspace. Based on the principle of virtual work with a simplifying hypothesis adopted, the dynamic model is established, and dynamic control utilizing computed torque method is implemented. At last, the experimental results made for the prototype illustrate the performance of the control algorithm well. This research will lay a good foundation for the development of a medical robot to assist in CPR operation.     

Robust PID control of fully-constrained cable driven parallel robots

In this paper dynamic analysis and robust PID control of fully-constrained cable driven parallel manipulators are studied in detail. Since in this class of manipulators cables should remain in tension for all maneuvers in their workspace, feedback control of such robots becomes more challenging than that of conventional parallel robots. In this paper, structured and unstructured uncertainties in dynamics of the robot are considered and a robust PID controller is proposed for the cable robot. To ensure that all cables remain in tension internal force concept is used in the proposed PID control algorithm. Then, robust stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov direct method and it is shown that by suitable selection of the PID controller gains, the closed-loop system would be robustly stable. Finally, the effectiveness of the proposed PID algorithm is examined through experiments on a planar cable driven robot and it is shown that the proposed control structure is able to provide suitable performance in practice.     

Adaptive robust control of fully-constrained cable driven parallel robots

In this paper, adaptive robust control (ARC) of fully-constrained cable driven parallel robots is studied in detail. Since kinematic and dynamic models of the robot are partly structurally unknown in practice, in this paper an adaptive robust sliding mode controller is proposed based on the adaptation of the upper bound of the uncertainties. This approach does not require pre-knowledge of the uncertainties upper bounds and linear regression form of kinematic and dynamic models. Moreover, to ensure that all cables remain in tension, proposed control algorithm benefit the internal force concept in its structure. The proposed controller not only keeps all cables under tension for the whole workspace of the robot, it is chattering-free, computationally simple and it does not require measurement of the end-effector acceleration. The stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov second method and it is shown that the tracking error will remain uniformly ultimately bounded (UUB). Finally, the effectiveness of the proposed control algorithm is examined through some experiments on a planar cable driven parallel robot and it is shown that the proposed controller is able to provide suitable tracking performance in practice.     

A patient-mounted robotic platform for CT-scan guided procedures

In this paper, we present a novel robotic assistant dedicated to medical interventions under computed tomography scan guidance. This compact and lightweight patient-mounted robot is designed so as to fulfill the requirements of most interventional radiology procedures. It is built from an original 5 DOF parallel structure with a semispherical workspace, particularly well suited to CT-scan interventional procedures. The specifications, the design, and the choice of compatible technological solutions are detailed. A preclinical evaluation is presented, with the registration of the robot in the CT-scan.     

Workspace and singularity analysis of a double parallel manipulator

A double parallel manipulator (DPM) is composed of two parallel mechanisms with a central aids. The device is expected to have large workspace by reducing interference between links and to avoid singularity by constraining its motion. To prove this, workspace and singularity are analyzed. The workspace of the device is decoupled into a positional and an orientational workspace, each of which is computed and compared with that of a Stewart platform. The singularities occurring outside the workspace are analytically found at the configurations where a Jacobian matrix becomes rank deficient. To ascertain the analytical results, they are geometrically examined at the configurations where the duty for resisting forces and moments is not properly shared by a central axis and linear actuators due to losing static equilibrium. The geometrical results are coincident to the analytical results, which proves the DPM is free from the singularity problem     

基于全局空间控制的高精度柔性视觉测量系统研究

针对传统机器人视觉测量系统中测量精度受机器人绝对定位精度限制的问题,构建了基于全局空间控制的高精度柔性视觉测量系统并研究其标定技术。通过全局空间测量定位系统实现机器人末端工具的高精度实时控制,可以突破机器人自身定位精度的限制,充分发挥其高度柔性的运动特性。为实现系统高精度测量,提出一种基于单应性矩阵的视觉传感器外参标定方法,该方法仅需对所设计的平面靶标进行一次成像,结合激光跟踪仪进行坐标转换即可实现传感器坐标系与外部参考坐标系之间坐标转换关系的精确标定。实验结果表明,基于全局空间控制的机器人视觉测量系统在其工作空间中距离测量精度优于0.2/mm,较传统的机器人视觉测量系统得到显著提高。     

Control of robotic object pivoting based on tactile sensing

Robotic manipulation of objects using the sole tactile feedback is a challenge. If the contact between the robot end effector and the manipulated object is distributed, the robot can exchange both friction forces and torques with it. The friction highly influences the motion of the object. By controlling the friction it is possible to perform complex manipulation tasks, such as moving the object with respect to the end effector by executing a controlled sliding motion. If the motion is a rotation with respect to the end effector, the corresponding maneuver is called pivoting. Control of the pivoting motion is considerably difficult, especially without any visual feedback. This paper proposes a novel method to regulate the object angular position, by means of a pivoting maneuver, through a parallel gripper endowed with force/tactile sensors. The strategy is based on a novel nonlinear observer that estimates the sliding velocity from force/torque measurements and a model of the sliding dynamics. We exploit the Limit Surface concept and the LuGre friction model to build a dynamic model of a planar slider. We show, through experimental results, that simple parallel grippers are able to execute such maneuvers that correspond to adding a virtual joint between the fingers, thus enlarging the robot workspace.     

Development of a six DOF haptic master for teleoperation of a mobile manipulator

An intuitive controller is needed for easier teleoperation of a slave robot. The mobile manipulation task requires three DOFs for planar mobility and six DOFs for 3-D manipulation. Since existing six DOF haptic devices have not been adequately developed for mobile manipulation, they are inefficient for planar three DOF motion. In this paper, a design for a six DOF haptic master suitable for tasks involving mobile manipulation is presented. The proposed device adopts a separable structure composed of lower and upper mechanisms. The lower parallel mechanism offers three DOFs for planar motion, and the upper parallel mechanism mounted on the lower mechanism provides the remaining three DOFs for a total of six DOFs; thus, the workspace can be extended into a full six DOF representation. This separable feature provided efficient actuation and reduced computational burden since only three actuators were involved in the planar task. Moving bodies should have low inertia to improve the back-drivability and transparency; therefore, all actuators were placed at the base, and torques were delivered via wire-driven transmission. A kinematic analysis was performed, and design parameters were determined through workspace analysis. Various experiments demonstrated that the proposed mechanism was efficient for a planar task, and also adequate for a full 3-D task.