Control of three-link underactuated manipulators using a switching method of fuzzy energy regions

In general, manipulators used for industry and in academic laboratories have actuators to drive each joint. On the other hand, underactuated manipulators handled by our research have some passive or free joints without actuators and brakes. We recently developed a switching method of fuzzy energy regions to control such manipulators. In such a method, it is necessary to design parameters related to energy regions and the gains of some partly stable controllers based on the computed torque method. Here, the switching method is applied for a three-link underactuated manipulator. We optimize such design parameters related to fuzzy energy regions by a genetic algorithm. The effectiveness of the present method is illustrated with some simulations. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

A PC-Based Simulator/Controller/Monitor Software for a Generic 6-DOF Manipulator

General form application is a very important issue in industrial design. Prototyping a design helps in determining system parameters, ranges and in structuring better systems. Robotics is one of the industrial design fields in which prototyping is crucial for improved functionality. Developing an environment that enables optimal and flexible design using reconfigurable links, joints, actuators and sensors is essential for using robots in the education and industrial fields. We propose a PC-based software package to control, monitor, and simulate a generic 6-DOF (six degrees of freedom) robot including a spherical wrist. This package may be used as a black box for the design implementations or as a white (detailed) box for learning about the basics of robotics and simulation technology.     

A Two-Layer Robot Controller Design Using Evolutionary Algorithms

The results obtained by a rule-based proportional, integral, derivative (PID) precompensator controller applied to a two-joint manipulator are discussed. The end effector is made to follow a specified trajectory obtained from the inverse kinematics by an appropriate design of a fuzzy control law. The desired trajectory is determined by the values of the joint variables and the structural kinematics parameters of the manipulator. The performance of the PID controller is exploited here to build a fuzzy precompensator that will enhance the conventional PID and to obtain better performances and results. The fuzzy rule base of the precompensator designed is found by associating two evolutionary algorithms that search for the optimal solution.     

Design and Testing of a Robotic System for mr Image-guided Interventions

The effective integration of robotics together with magnetic resonance (mr) technology is expected to facilitate the real-time guidance of various diagnostic and therapeutic interventions. Specially designed robotic manipulators are required for this purpose, the development of which is a challenging task given the strong magnetic fields and the space limitations that characterize the mr scanning environment. A prototype mr-compatible manipulator is presented, designed to operate inside cylindrical mr scanners. It was developed for the study of minimally invasive diagnostic and therapeutic interventions in the abdominal and thoracic area with real-time mr image guidance. Initial tests were performed inside a high-field clinical mr scanner and included mr-compatibility tests and phantom studies on image-guided targeting.     

轮式移动平台两构形间运动变换对机械手的影响

本文研究了连接轮式移动平台两构形的3种路径对机械手的影响．指出需要逆路径连 接的构形在规划移动机械手两构形时应尽量避免使用,对机械手来说移动平台的最好构形应 处于能用直接路径连接的区域内,在进行移动机械手协调规划时不应忽略这点,并为移动机 械手优化准则的提出奠定了基础．     

机械手空间圆弧位姿轨迹规划算法的实现

为提高机械手的空间圆弧作业任务的轨迹精度,提出采用齐次矩阵和四元数法分别进行位置和姿态的轨迹规划方法．对于位置规划,先对空间圆弧所在平面的圆心角做归一化处理,再按照平滑角速度曲线规划位置轨迹上的插值点,并用齐次矩阵表示插补点的位置,保证了插补点的位置始终在所求圆弧上．姿态规划采用四元数圆弧曲线函数以及分段三次有理插值保形样条函数实现C²连续的姿态轨迹．算例验证表明,提出的位姿规划方法能够保证机械手末端执行器的轨迹精度,在位置精度及姿态平稳过渡有较高要求的机械手的实际应用方面有推广价值．     

交叉型平面二自由度移动并联机构运动学性能分析

为研究一种新型平面二自由度移动并联机构的运动学性能,建立其运动学模型,推导出位置正/逆解的解析表达式,定义运动学性能指标,分析不同构型的性能指标表达式,探讨性能指标与机构尺寸之间的关系,并绘制相关的性能图谱.得到该并联机构具有较大有效工作空间与机架尺寸比值、导轨长度短等优点.这些性能图谱为该并联机构的优化提供了参考.     

A 6-DOF adaptive parallel manipulator with large tilting capacity

In this paper, a novel 6 degrees of freedom (DOFs) adaptive parallel manipulator with large tilting capacity is presented. The manipulator consists of four identical peripheral limbs and one center limb connecting the base and the moving platform. Due to the special architecture, the doubly actuated center limb of the manipulator could have infinite inverse solutions. In every configuration of the end-effector, the manipulator can adapt its center limb to the position and orientation with best dexterity. An optimization equation for obtaining the optimized dexterity of the manipulator is introduced to solve this nonholonomic problem, which also makes the manipulator capable of large tilting capacity. Targeting for the application of five-face machining, the detailed kinematic analysis of the manipulator is developed, which includes the closed-form solutions of inverse position problems, the singularity, dexterity, workspace and tilting capability. The analysis developed in this paper shows that the proposed manipulator has large tilting capacity and thus a suitable candidate for five-face machining.     

约束力/矩对一种少自由度并联机构刚度及弹性变形的影响

研究约束力/矩对一种3UPS+RRPR少自由度并联机构的总刚度与弹性变形的影响。以主动约束力/矩为基础求解3UPS+RRPR少自由度并联机器人机构的刚度与弹性变形。首先分析该并联机构受力位置并确定主动约束力/矩的姿态。然后,分析该并联机构的主动约束分支的弹性变形,并解出主动约束分支的伴随矩阵。基于6×6的雅可比矩阵和主动约束分支的伴随矩阵,导出该并联机构的总刚度矩阵和弹性变形。最后得出结论:约束力/矩对该并联机构的弹性变形产生巨大的影响,当建立总刚度矩阵和弹性变形时,必须考虑约束力/矩。