Nonholonomic Mobile Manipulators: Kinematics, Velocities and Redundancies

We consider nonholonomic mobile manipulators built from an n _a joint robotic arm and a nonholonomic mobile platform with two independently driven wheels. Actually, there is no efficient kinematic formalism for these systems which are generally characterized by their high number of actuators. So, kinematic modelling is presented with particular emphasis on redundancy. Whereas kinematic redundancy is well known in the holonomic case, it is pointed out that it is necessary to define velocity redundancy in the case of nonholonomic systems. Reduced velocity kinematics based on quasi-velocities are shown to provide an efficient formalism. Two examples of mobile manipulators are presented. Finally, reduced velocity kinematics and velocity redundancy are shown to be adequate tools in order to realize operational task while optimizing criteria such as manipulability.     

利用AutoCAD求解机构运动学和动力学问题

提出采用AutoCAD求解机构运动学和动力学问题,并结合实例给出了方法与步骤。 此求解法既有图解法简单明了的特点,又能满足了现代机械设计对运动分析和动力分析的高精度 的要求,具有较高的可靠性和实用性。     

A simple method to solve the forward displacement analysis of the general six-legged parallel manipulator

In this work a simple method to solve the forward displacement analysis of the general 6-6 fully parallel manipulator is applied. The method is based on generating closure equations upon the unknown coordinates of three points embedded to the moving platform. The method is easy to follow and it is available for both, planar and three-dimensional moving platforms. Numerical examples are included with the purpose to show the application of the method.     

Grasping objects localized from uncertain point cloud data

Robotic grasping is very sensitive to how accurate is the pose estimation of the object to grasp. Even a small error in the estimated pose may cause the planned grasp to fail. Several methods for robust grasp planning exploit the object geometry or tactile sensor feedback. However, object pose range estimation introduces specific uncertainties that can also be exploited to choose more robust grasps. We present a grasp planning method that explicitly considers the uncertainties on the visually-estimated object pose. We assume a known shape (e.g. primitive shape or triangle mesh), observed as a–possibly sparse–point cloud. The measured points are usually not uniformly distributed over the surface as the object is seen from a particular viewpoint; additionally this non-uniformity can be the result of heterogeneous textures over the object surface, when using stereo-vision algorithms based on robust feature-point matching. Consequently the pose estimation may be more accurate in some directions and contain unavoidable ambiguities.The proposed grasp planner is based on a particle filter to estimate the object probability distribution as a discrete set. We show that, for grasping, some ambiguities are less unfavorable so the distribution can be used to select robust grasps. Some experiments are presented with the humanoid robot iCub and its stereo cameras.     

数字皮影动画脚本的研究与应用

为简化数字皮影动画的制作流程,提高数字皮影作品的交互性,降低数字皮影实时表演的难度,对皮影常见角色及动作进行了抽象、分类,提出一种针对特定类型的通用的骨骼模型。基于反向动力学,设计了一套描述皮影骨骼动画的脚本。该脚本通过对骨骼位置与旋转属性的控制定义皮影角色的基本动作,并通过对基本动作的叠加实现复杂动作。脚本对动作的定义基于骨骼模型而非具体角色,具有通用性。最后通过实验证明了脚本的有效性。     

冗余度机器人扩展雅克比方法的应用研究

采用基于所提出的连续比例因子的梯度投影法,利用模糊推理规则动态求解了多性能指标融合中的权系数,对卫星在轨自维护系统的冗余度机器人推拉帆板作业进行了数值仿真计算。所得到的结果与采用固定比例因子的梯度投影法进行了比较,指出了采用固定比例因子方法的不足之处。实验结果验证了所提出的连续比例因子方法的可行性,为冗余自由度机器人的逆运动学解法提供了新思路。     

MOTOMAN-HP3型机器人运动学建模

根据MOTOMAN-HP3型机器人具体结构特点,建立机器人的运动学模型,求出正逆解.并在机器人运动学建模过程中,对关节运动范围的转换规律进行了研究.为机器人运动分析、离线编程、轨迹规划等打下了基础.     

EPB盾构掘进机刀具运动学建模分析

EPB盾构掘进机的刀盘上可根据切削土质的软硬而选择安装硬岩刀具和软土刀具。通过运用空间几何理论以及空间运动学的坐标变换矩阵法对刀盘上安装的正滚刀、边滚刀以及切刀的破岩过程进行分析,得出了刀具破岩的运动规律,建立了刀具工作刀刃的破岩运动学模型。模型的建立有利于对刀具进行磨损和破岩机理以及刀具优化设计的研究。     

移动机械手的整体运动学建模与控制

移动机械手由一个机械手固定安装在一个移动平台上构成。移动平台和机械手的不同物理特性使移动机械手的建模和协调控制成为机器人领域的难点之一。本文对移动机械手进行了运动学分析,给出了其整体运动学建模方法;针对移动机械手的非线性和强耦合特点,设计了PD反馈控制器;仿真实验证明该控制器具有良好的控制效果。