人手的运动学仿真及基于知识的控制方法

在对手部结构进行分析的基础上,给出了受约束的人手运动学模型,并重点研究了基于虚拟现实的人手运动仿真,建立了虚拟手遥控操作仿真实验系统,通过它进行单指、成组和整手控制,并实现了基于知识的抓取操作。     

Effect of Nonlinear Wave Kinematics on Dynamic Response of Spars

The difference between various approximate methods to compute the wave kinematics and forces acting on a Spar platform up to the instantaneous free water surface is investigated. Three types of procedures are considered; i.e., extrapolation, stretching (both simple extensions of linear wave theory) and the hybrid wave model (which involves decomposition of the incident wave into first- and second-order components). Of particular interest for the dynamic response of a Spar are the nonlinear (second- and higher-order) low-frequency forces. The effects of the different procedures are compared analytically and numerically for the inertia forces using Morison et al.’s equation as reported in 1950, but the conclusions can be extended to diffraction theory formulations.     

Kinematic Soil-Structure Interaction from Strong Motion Recordings

Earthquake strong motion recordings from 29 sites with instrumented structures and free-field accelerographs are used to evaluate variations between foundation-level and free-field ground motions. The focus of the paper is on buildings with surface and shallowly embedded foundations. The foundation/free-field ground motion variations are quantified in terms of frequency-dependent transmissibility function amplitude ∣H∣. Procedures are developed to fit to ∣H∣ analytical models for base slab averaging for the assumed conditions of a rigid base slab and a vertically propagating, incoherent incident wave field characterized by ground motion incoherence parameter κ. The limiting assumptions of the model are not strictly satisfied for actual structures, and the results of the identification are apparent κ values (denoted κa) that reflect not only incoherence effects, but also possible foundation flexibility and wave inclination effects. Nonetheless, a good correlation is found between κa values and soil shear wave velocity for sites with stiff foundation systems. Based on these results, recommendations are made for modifying free-field ground motions to estimate base slab motions for use in response analyses of buildings.     

Face Stability Analysis of Circular Tunnels Driven by a Pressurized Shield

The aim of this paper is to determine the face collapse pressure of a circular tunnel driven by a pressurized shield. The analysis is performed in the framework of the kinematical approach of limit analysis theory. It is based on a translational three-dimensional multiblock failure mechanism. The present failure mechanism has a significant advantage with respect to the existing limit analysis mechanisms developed in the case of a frictional soil: it takes into account the entire circular tunnel face and not only an inscribed ellipse to this circular area. This was made possible by the use of a spatial discretization technique. Hence, the three-dimensional failure surface was generated “point by point” instead of simple use of existing standard geometric shapes such as cones or cylinders. The numerical results have shown that a multiblock mechanism composed of three blocks is a good compromise between computation time and results accuracy. The present method significantly improves the best available solutions of the collapse pressure given by other kinematical approaches. Design charts are given in the case of a frictional and cohesive soil for practical use in geotechnical engineering.     

序列式柑桔压榨机机构运动学的计算机仿真

对序列式柑桔压榨机的主要机构进行运动学分析,推导了柑桔压榨机的机构运动学参数的表达式,提出了用计算机对它们的运动学仿真方法。该仿真方法为柑桔压榨机的机构的动力学分析打下了基础,可迅速地检查设计参数的合理性及工作性能。     

Position Error Modeling for Automated Construction Manipulators

Hydraulically actuated construction equipment is rapidly being retrofitted with robotic control capabilities by several major manufacturers. However, position control errors caused by several factors are significant in these types of construction equipment. Errors are amplified if the manipulator and its operator must measure and locate objects in the equipment’s fixed reference frame. Both mechanistic and statistical approaches to correcting position errors are possible. A statistical approach is reported here that is validated based on experiments with a computer-controlled large-scale manipulator (LSM). The LSM is sufficiently representative of several types of construction equipment to be able to serve as a general test bed. In the regression analysis, three factors which are measurable in real time: distance, hydraulic pressure, and payload, were varied to determine their influence on position errors in the LSM. It was shown that with an integrated multivariable regression model, about 30% of the mean positioning error of the LSM can be reduced without the use of fixed external reference systems. The model can be implemented as simple, real-time regression equations.     

数值方法在铰链四连杆机构运动分析的应用

针对铰链四连杆机构运动设计解析法的复杂性,在建立机构运动几何方程的基础上,利用牛顿迭加法进行数值求解.通过对不同步长以及差分格式的选取比较,确定了计算杆件速度和加速度的合适的差分公式.运用Matlab语言强大的计算及图形可视化功能,获得了精确的数值结果和提高了设计的效率.     

Anti-swing control of a hydraulic loader crane with a hanging load

In this paper, anti-swing control for a hydraulic loader crane is presented. The difference between hydraulic and electric cranes are discussed to show the challenges associated with hydraulic actuation. The hanging load dynamics and relevant kinematics of the crane are derived to create the 2-DOF anti-swing controller. The anti-swing controller is added to the electro-hydraulic motion controller via feedforward. A dynamic simulation model of the crane is made, and the control system is evaluated in simulations with a path controller in actuator space. Simulation results show significant reduction in the load swing angle during motion. Experiments are carried out to verify the performance of the anti-swing controller, showing good suppression of the payload angle in practice.     

一种舰载稳定平台运动学分析

根据舰船在海洋中的运动特性,本文提出一种由五个结构完全相同的UPS型驱动分支和一个RRS型约束分支构成的五自由度舰载稳定平台,该平台可实现三维转动和两维移动。首先,本文建立了该稳定平台的三维模型,并推导了其运动学反解表达式;其次,建立了该稳定平台正向和逆向速度、加速度表达式,并通过实例分析画出了5个驱动分支的位移、速度和加速度曲线图,通过运动学曲线图可看出该稳定平台运动平稳,其位移、速度以及加速度均未出现突变或断点,表明机构设计的正确性,并具有较好的运动学特性。     

错架图书识拣机器人结构设计及运动学分析

设计了一个四自由度直角坐标错架图书分拣机器人,传动机构由一个R方向的转动机构和X、Y、Z 3个方向上的滑动机构组成,通过各个传动机构的运动实现末端执行器所要到达的位置。利用D-H参数法建立机器人的运动学方程,对机器人末端执行机构的运动进行理论推导,利用SolidWorks进行建模,将模型导入到ADAMS软件中进行运动学仿真。结果表明:机器人末端位移、速度曲线变化平稳,能到达空间中的指定位置,验证了结构设计的合理性,从而为控制系统的设计提供了依据。