A method for the reduction of skin marker artifacts during walking : Application to the knee

Previous studies have demonstrated the importance of joint angle errors mainly due to skin artifact and measurement errors during gait analysis. Joint angle errors lead to unreliable kinematics and kinetic analyses in the investigation of human motion. The purpose of this paper is to present the Joint Averaging Coordinate System (JACS) method for human gait analysis. The JACS method is based on the concept of statistical data reduction of anatomically referenced marker data. Since markers are not attached to rigid bodies, different marker combinations lead to slightly different predictions of joint angles. These different combinations can be averaged in order to provide a “best” estimate of joint angle. Results of a gait analysis are presented using clinically meaningful terminology to provide better communication with clinical personal. In order to verify the developed JACS method, a simple three-dimensional knee joint contact model was developed, employing an absolute coordinate system without using any kinematics constraint in which thigh and shank segments can be derived independently. In the experimental data recovery, the separation and penetration distance of the knee joint is supposed to be zero during one gait cycle if there are no errors in the experimental data. Using the JACS method, the separation and penetration error was reduced compared to well-developed existing methods such as ACRS and Spoor & Veldpaus method. The separation and penetration distance ranged up to 15 mm and 12 mm using the Spoor & Veldpaus and ACRS method, respectively, compared to 9 mm using JACS method. Statistical methods like the JACS can be applied in conjunction with existing techniques that reduce systematic errors in marker location, leading to an improved assessment of human gait.     

Kinematics analysis of a hybrid manipulator for computer controlled ultra-precision freeform polishing

As one of the final processing steps of precision machining, polishing process is a very key decision for surface quality. This paper presents a novel hybrid manipulator for computer controlled ultra-precision (CCUP) freeform polishing. The hybrid manipulator is composed of a three degree-of-freedom (DOF) parallel module, a two DOF serial module and a turntable providing a redundant DOF. The parallel module gives the workpiece three translations without rotations. The serial module holds the polishing tool and gives it no translations on the polishing contact area due to its particular mechanical design. A detailed kinematics model is established for analyzing the kinematics of the parallel module and the serial module, respectively. For the parallel module, the inverse kinematics, the forward kinematics, the Jacobian matrix, the workspace and the dexterity distribution are analyzed systematically. Workspaces are also investigated for varying structural parameters. For the serial module, the inverse kinematics, the forward kinematics, the workspace and the precession motion analysis are carried out. An example of saddle surface finishing with this manipulator is given and the movement of actuators with respect to this shape is analyzed theoretically. These analysis results illustrate that the proposed hybrid manipulator is a very suitable machine structure for CCUP freeform polishing.     

AutoCAD系统中运动副仿真系统的构造

根据运动副的特点，运用AutoCAD计算机辅助设计系统，以提高设计工作效率和正确性为目的，讨论了运动副仿真系统的构造及其具体应用。     

RRR-RRP六杆机构的MATLAB运动学仿真

用复数推导了曲柄、RRR和 RRP 级杆组的位移、速度和加速度的复数表达式 ,并将其转化为适用于MATL AB仿真的矩阵数学模型 ,以该矩阵数学模型编制了相应的 M函数仿真模块 ,对给定的 RRR- RRP六杆 级机构为例说明如何使用这三个仿真模块建立 MATL AB仿真模型 ,并对其仿真结果的正确性加以分析。其主要思想是以组成机构的杆组为仿真模块 ,搭建各种机构 MATL AB仿真模型 ,可以对各种低副机构进行运动学仿真和分析     

5-UPS/PRPU 5自由度并联机床运动学分析

介绍了一种新型的5-UPS/PRPU5自由度并联机床,定平台通过五个结构完全相同的驱动分支UPS分支以一个约束分支PRPU分支与动平台相连接。该机床可以实现三维移动和两维转动,PRPU分支关节变量反映了动平台位姿,为实现闭环控制提供了条件。通过对其运动学进行分析和计算,确定了中间分支对动平台的约束运动,建立了该机床的运动学反解方程和雅可比矩阵,并通过机床样机试验验证了理论分析的正确性。     

Transient EHL analysis on spur gear teeth with consideration of gear kinematics

Transient 3-dimensional elasto-hydrodynamic lubrication (EHL) analysis is performed on the contacting teeth surfaces of involute spur gears. Kinematics of the gear and the pinion are taken into account to get accurate geometric clearance around the EHL region of the contacting teeth. The surface pressure and film thickness distribution for the whole contact faces in a lubricated condition at several time steps are obtained through the analysis. Besides the pressure spike at the outlet region, a representative phenomenon in EHL regime, the pressure at the inlet region is slightly higher than that of the center region. The film thickness of transient condition is thicker than that of steady condition.     

轮式小型甘蔗收割机行走系统的运动仿真分析

这里论述了轮式小型甘蔗收割机行走系统的研究方法，结合虚拟样机技术对其进行仿真分析和参数优化，利用该方法提高了行走系统的设计质量，该方法为轮式小型甘蔗收割机行走系统产品的开发和改进提供了有利的手段。     

FSAE赛车双横臂前悬架运动学仿真及优化

应用机械系统动力学分析软件ADAMS,建立方程式赛车双横臂独立前悬架模型.在ADAMS/Car中,对其进行了运动学仿真分析,得到了车轮跳动时各项参数的变化规律.利用ADAMS/Insight对悬架的某些硬点位置进行了优化.结果表明,悬架系统的运动学特性得到改善.     

一般多体系统位移分析的变换矩阵法

本文阐明了各种共轭副即接头（包括各种低副和各种高副）的运动学参变量,建立了各种接头连接的两构件之间相对运动的变换关系式。以回路制的方程为基础,建立了一般多体系统位移分析变换矩阵法的统一数学模型。该模型与建立在D-H描述基础上的低副机构位移分析变换矩阵法的数学模型一致。因此,彻底解决了高副、低副运动学分析的数学模型建立的问题。     

基于运动可优化度的冗余自由度机器人运动学实时控制研究

为解决冗余自由度机器人的运动学实时控制问题,给出了冗余自由度机器人运动学速度级的解析解。针对机器人系统振动及多性能指标融合控制,提出了“运动可优化度”的概念,并引入了运动可优化度函数。仿真和实践结果证明了这一新的控制方案的有效性。