基于神经网络的并联3自由度机器人位置正解

并联机器人位置正解是机器人运动学中难点问题之一，常规求解方法比较复杂且难度较大，通常需要对大量的非线性方程组进行推导计算且得到的解不唯一。该文提出了一种将人工神经网络用于并联机器人位置正解求解的通用方法，并结合实际机构对并联3自由度机器人进行了具体求解。通过对神经网络拓扑结构的设计以及选取有效的学习算法并用大量的位置反解数据对神经网络进行训练，获得了用于求解位置正解的神经网络模型，该网络可以实现位置正解问题的求解计算，从而避免了复杂的推导和演算。计算机仿真与实验结果表明了该方法的有效性与可行性。     

空间缩放式六自由度并联平台机构及位置分析

本文提出了一种以缩放机构为分支的新型六自由度空间并联机器人机构模型．文中讨论了它的机构学特点，给出了位置反解的方法，推导出了位置正解的８次封闭解法，并进行了数值验证．     

平行导路6-PSS并联机构运动学研究

文中提出了一种新型平行导路6-PSS结构并联机器人,介绍了这种机构的特点并对其运动学相关算法进行了深入研究,其中包括运动学反解、雅可比矩阵以及正解的求解方法,同时还与6-SPS结构并联机器人运动学相关的算法进行了比较.由于文中采用构造法计算雅可比矩阵,避免了以往对反解方程直接求导的计算方式,从而使雅可比矩阵的计算大为简化,而且也减少了正解的计算量、精度得到提高.实验结果证明,这些算法正确、实用.     

工业用并联机器人位置正解的精确求解

利用工业用6-DOF并联机器人位置反解易于获得这一特性,把较难的六自由度并联机器人位置正解问题转化为应用位置反解结果作为训练样本进行学习,从而实现机械手从关节变量空间到工作变量空间的非线性映射。文中以工业用6-DOF并联机器人为例,采用BP算法对其正解进行了求解,并利用Matlab进行仿真,结果表明该方法计算精度高,克服了数值解法的求解精度受初值影响较大的缺点。经过验证,BP网络的求解精度满足了控制精确的要求。     

旋转输入型并联机器人位置逆解分析的轨迹圆法

本文分析了几种典型旋转输入型并联机器人的机构形式和特点，提出了适用于各种旋转输入型并联机器人位置逆解分析的轨迹圆法，利用该方法可方便地进行位置逆解建模与求解、逆解情况（有无解及多解性）判断等，简化了位置控制算法     

用连续法求一类混合链机器人机构的全部位置正解

本文对一类混合链机器人机构的位置正解问题进行了研究。首先用Ｄ－Ｈ矩阵法建立机构上下平台之间的坐标转换关系；然后利用杆长约束条件得到机构的位置正解方程组；最后应用连续法直接求出其全部位置正解。本文方法形式简洁、求解方便，且具有一般性，可推广应用于其他类型混合链机器人机构及并联机器人机构的位置正解研究。     

基于位置反解算法的并联机器人坐标变换方法

目的为提高工作效率,提升工业机器人的可靠性、稳定性和运动精度,避免机器人出现速度以及加速度的突变,对机器人的位置进行准确的控制。方法 以RBT-6T03P并联机器人为例,应用坐标变化法和位置反解算法对并联机器人机构的位置坐标进行分析并利用MATLAB进行仿真。结果 结果表明：通过位置反解对并联机器人的坐标进行变换求解是方便可行。结论 所述控制方法相对于并联机器人求正解算法更加简单、方便、快捷。     

空间六自由度多回路机构位置的三维搜索方法

本文以并联多回路6—SPS 机构位置反解方程为基础、得到了以非线性方程组形式表达的求解6—SPS 机构位置正解的“三维优化算法”求解公式.与现有的该机构位置正解算法相比该方法使原来解搜索维数由六维降至三维,因此,具有计算速度快,初值易于选取等优点.     

冗余并联机构的力控制

为了实现力反馈遥操作系统中的力反馈,介绍了一种用作力反馈主手的驱动冗余并联机构,并提出了一种简单的力控制算法。这种方法首先由机构的逆解计算其力映射矩阵、雅可比矩阵。然后,基于消除冗余并联机构固有内力的原则,由冗余并联机构的末端力得到机构各个主动关节的驱动力。由于并联机构的逆解比正解简单,这种方法能够大大地简化计算。实验结果表明,这种算法能快速、精确地完成力控制。     

面向冗余机器人实时控制的逆运动学求解有效方法

针对7自由度冗余机器人实时运动控制,对机器人逆运动学提出了一种新的求解方法.采用位姿分解方式,使7自由度冗余机器人逆运动学简化为4自由度位置逆运动学求解.在梯度投影法得到位置优化解的基础上,利用机器人封闭解公式求得一组优化解.通过对7自由度机器人仿真分析,表明了该方法的有效性.     

Forward and inverse kinematics of a 5-DOF hybrid robot for composite material machining

Hybrid robots consist of both serial and parallel mechanisms, which have advantages in stiffness and workspace compared with serial/parallel robots when machining composite material. However, the forward and inverse kinematics of hybrid robots generally do not have analytic solutions. This paper deals with the analytic forward and inverse kinematics solutions of a 5-degree-of-freedom (DOF) hybrid robot which consists with a 3-DOF 2UPU/SP parallel mechanism (PM) and a 2-DOF rotating head. In the forward kinematic problem, a method is proposed to transfer the high order kinematic equation to a 4th-order polynomial based on the Sylvester's dialytic elimination, and the analytic solutions can be further obtained by Ferrari's method. In the inverse problem, the redundant Euler angles expressed by four rotations are firstly proposed for decoupling different motions, then, the closed-form solution of inverse kinematics can be found. Finally, a simulation trajectory is given, and the result shows that the accuracy of the solutions’ calculation reaches femtometer grade and the efficiency reaches microsecond grade; furthermore, an experiment is performed on the prototype to validate the effectiveness of the proposed forward and inverse kinematics.     

Inverse statics analysis of planar parallel manipulators via Grassmann-Cayley algebra

The wrench Jacobian matrix plays an important role in the statics and singularity analysis of planar parallel manipulators (PPMs). The Jacobian matrix can be calculated based on the conventional Plücker coordinate method. However, this method cannot be applied when two links are in parallel. A new approach is proposed for the analysis of the forward and inverse wrench Jacobian matrix using Grassmann-Cayley algebra (GCA). A symbolic formula for the inverse statics analysis is obtained based on the Jacobian. The proposed method can be applied when two links are in parallel. The approach is explained in detail based on a planar 3-RPR PPM example, and the analysis procedure for nine other PPMs is also presented. This novel approach to deriving the statics can be applied to spatial parallel manipulators and redundant cases of PPMs.

     

新型欠秩并联机器人机构3RRC仿真

分析了并联机器人机构3RRC的输入输出特性,给出了位置分析和连杆运动干涉分析。以directX为仿真引擎,vc6为软件平台,采用面向对象方法封装了机构正反解算法,编写了仿真软件,实现了该机器人机构运动学动态仿真,为类似机构结构设计和特性研究提供了有益参考。     

冗余自由度超声检测机器人的逆运动学分析

针对一类冗余自由度超声检测机器人的传统逆运动学求解算法耗时长且准确度低的问题,提出了一种基于集合划分和解析解法相结合的逆运动学求解算法。首先采用De-navit-Hartenberg方法建立检测机器人的运动学方程;其次,利用解析解法求出机器人逆解的解析表达式,并提出三种自由度分配方案;最后,选择合适的自由度分配方案,据此对超声波探头位姿集合作划分,结合逆解解析式求出运动学逆解。实际应用中,借助十一轴超声波检测机器人,利用该算法对具有复杂外形的飞机螺旋桨叶片进行检测。结果表明,与传统的纯数值解法相比,该算法能够快速得到精确的运动学逆解。     

Reliability-based approach to the inverse kinematics solution of robots using Elman's networks

The solution of inverse kinematics problem of redundant manipulators is a fundamental problem in robot control. The inverse kinematics problem in robotics is the determination of joint angles for a desired cartesian position of the end effector. For the solution of this problem, many traditional solutions such as geometric, iterative and algebraic are inadequate if the joint structure of the manipulator is more complex. Furthermore, many neural network approaches have been done to this problem. But the neural network-based solutions are not much reliable due to the error at the end of learning. Therefore, a reliability-based neural network inverse kinematics solution approach has been presented, and applied to a six-degrees of freedom (dof) robot manipulator in this paper. The structure of the proposed method is based on using three networks designed parallel to minimize the error of the whole system. Elman network, which has a profound impact on the learning capability and performance of the network, is chosen and designed according to the proposed solution method. At the end of parallel implementation, the results of each network are evaluated using direct kinematics equations to obtain the network with best result.     

一种新型简单6－SPS并联机器人及其位置正解

本文提出一种新型简单６－ＳＰＳ并联机器人机构，给出了它的变形型式并讨论了其位置正解．该机构的位置正解通过依次求解三个一元二次代数方程即可得到．本文最后给出了数值实例．     

Inverse kinematics of planar redundant manipulators via virtual links with configuration index

This article presents a new method for generating inverse kinematic solutions for planar manipulators with large redundancy (hyper-redundant manipulators). The proposed method starts by decomposing a planar redundant manipulator into a series of local planar arms that are either 2-link or 3-link manipulator modules, and connecting the conjunction points between them with virtual links. The manipulator then can be handled by a simple virtual link system, which may be conveniently divided into non-singular and singular cases depending on its configuration. When the virtual link system is no longer effective due to a singular configuration, the displacement of the end-effector is then allocated to virtual links according to a displacement distribution criterion. A dexterity index called the “configuration index” distinguishes the non-singular and singular cases. The concept of virtual link is shown by computer simulations to be simple and effective for the inverse kinematics of a planar hyper-redundant manipulator with a discrete model. In particular, it can be applied to solving the inverse kinematics of a SCARA-type spatial redundant manipulator whose redundancy is included in its planar mechanism. © 1994 John Wiley & Sons, Inc.     

Performance Analysis and Application of a Redundantly Actuated Parallel Manipulator for Milling

This paper deals with the performance analysis of a 3-degree-of-freedom (3-DOF) planar parallel manipulator with actuation redundancy. Closed-form solutions are developed for both the inverse and direct kinematics about the redundant parallel manipulator. In performance analysis phase, the dexterity is analyzed, three kinds of singularities are investigated, and the stiffness is estimated. Compared with the corresponding non-redundant parallel manipulator with the redundant link removed, the redundantly actuated one has better dexterity, litter singular configurations and higher stiffness. The redundantly actuated parallel manipulator was applied to the design of a 4-DOF hybrid machine tool which also includes a feed worktable to demonstrate its applicability.     

Dynamic formulation of a planar 3-DOF parallel manipulator with actuation redundancy

In this paper, based on the conventional Newton–Euler approach, a simplification method is proposed to derive the dynamic formulation of a planar 3-DOF parallel manipulator with actuation redundancy. Closed-form solutions are developed for the inverse kinematics. Based on the kinematics, the Newton–Euler approach in simplification form is used to derive the inverse dynamic model of the redundant parallel manipulator. Then, the driving force optimization is performed by minimizing an objective function which is the square of the sum of four driving forces. The dynamic simulations are done for the parallel manipulator with both the redundant and non-redundant actuations. The result shows that the dynamic characteristics of the manipulator in the redundant case are better than that in the non-redundancy. The redundantly actuated parallel manipulator was incorporated into a 4-DOF hybrid machine tool which includes a feed worktable.