A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to inve...A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to investigate this PKM.Based on this method,kinematic,velocity and error models of this manipulator are established respectively.Since3-PRS PKM has been applied successfully in practice and its structure is similar to the 3-P(Qu) RU PKM,corresponding models of a 3-PRS PKM are given and a performance comparison study between them is investigated on workspace,manipulator dexterity,position error and error sensitivity.The comparison results reveal that the 3-P(Qu) RU PKM has the advantage on velocity performance and the disadvantage on accuracy performance.This novel 3-P(Qu) RU PKM is an available selection for a tool head of a hybrid machine tool and the analysis is greatly helpful for the further applications of this manipulator.展开更多
The development of new robot structures, in particular of parallel kinematic machines（PKM）, is widely systematized by different structure synthesis methods. Recent research increasingly focuses on PKM with less than...The development of new robot structures, in particular of parallel kinematic machines（PKM）, is widely systematized by different structure synthesis methods. Recent research increasingly focuses on PKM with less than six degrees of freedom（DOF）. However, an overall comparison and evaluation of these structures is missing. In order to compare symmetrical PKM with three translational DOF, different evaluation criteria are used. Workspace, maximum actuation forces and velocities, power, actuator stiffness, accuracy and transmission behavior are taken into account to investigate strengths and weaknesses of the PKMs. A selection scheme based on possible configurations of translational PKM including different frame configurations is presented. Moreover, an optimization method based on a genetic algorithm is described to determine the geometric parameters of the selected PKM for an exemplary load case and a prescribed workspace. The values of the mentioned criteria are determined for all considered PKM with respect to certain boundary conditions. The distribution and spreading of these values within the prescribed workspace is presented by using box plots for each criterion. Thereby, the performance characteristics of the different structures can be compared directly. The results show that there is no ＂best＂ PKM. Further inquiries such as dynamic or stiffness analysis are necessary to extend the comparison and to finally select a PKM.展开更多
基于全球导航卫星系统(global navigation satellite system,GNSS),采用精密单点定位(precise point positioning,PPP)技术的低轨卫星运动学定轨是广泛研究的热点。然而不同低轨卫星搭载星载接收机性能不同,基于其星载GNSS数据的运动学...基于全球导航卫星系统(global navigation satellite system,GNSS),采用精密单点定位(precise point positioning,PPP)技术的低轨卫星运动学定轨是广泛研究的热点。然而不同低轨卫星搭载星载接收机性能不同,基于其星载GNSS数据的运动学定轨效果也会有所差异。本文首先介绍了GARCE-FO卫星和Swarm卫星及其星载接收机,然后从观测卫星数、伪距多路径以及信号强度对比其数据质量差异,最后基于武汉大学开源的PIRDE PPP-AR软件解算其相应的运动学轨道进行对比。结果表明,GRACE-FO卫星相比Swarm卫星可观测到的GNSS卫星数更多,其各自的伪距多路径分别为0.16~0.19m和0.3~0.44m,并且GRACE-FO卫星的信号强度分布6~9之间,而Swarm卫星L2频率上的信号强度分布在1~7之间。综合来说,Swarm卫星的观测数据质量劣于GRACE-FO。此外,GRACE-FO卫星的模糊度残差表现出良好的近正态分布特性,宽巷模糊度和窄巷模糊度的固定率可达99%和93%,而Swarm卫星的窄巷模糊度残差则分布不规则。与权威机构发布的精密科学轨道对比,GRACE-C在切向、法向和径向3个分量固定解的轨道精度分别为1.39cm、0.98cm和2.59cm,GRACE-D卫星轨道精度与GRACE-C卫星整体一致;Swarm卫星各分量的运动学轨道精度则在3~4 cm左右,相较于GRACE-FO卫星要低1~2 cm。在平差解算时降低参数之间的相关性能有效提高参数估值的精度,使用随机游走估计GRACE-FO卫星的接收机钟差来相较于白噪声在径向分量上有60%左右的提升。此外,欧洲定轨中心(Center for Orbit Determination in Europe,CODE)发布的Swarm卫星运动学轨道以简化动力学解算得到的模糊度作为约束来降低参数相关性,相较于本文解算的运动学轨道在径向分量上也有一定的提升。展开更多
基金Supported by the National Natural Science Foundation of China(No.51575307,51225503)the Science and Technology Major Project-Advanced NC Machine Tools & Basic Manufacturing Equipments(No.2013ZX04004021,2014ZX04002051)Top-Notch Young Talents Program of China
文摘A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to investigate this PKM.Based on this method,kinematic,velocity and error models of this manipulator are established respectively.Since3-PRS PKM has been applied successfully in practice and its structure is similar to the 3-P(Qu) RU PKM,corresponding models of a 3-PRS PKM are given and a performance comparison study between them is investigated on workspace,manipulator dexterity,position error and error sensitivity.The comparison results reveal that the 3-P(Qu) RU PKM has the advantage on velocity performance and the disadvantage on accuracy performance.This novel 3-P(Qu) RU PKM is an available selection for a tool head of a hybrid machine tool and the analysis is greatly helpful for the further applications of this manipulator.
文摘The development of new robot structures, in particular of parallel kinematic machines（PKM）, is widely systematized by different structure synthesis methods. Recent research increasingly focuses on PKM with less than six degrees of freedom（DOF）. However, an overall comparison and evaluation of these structures is missing. In order to compare symmetrical PKM with three translational DOF, different evaluation criteria are used. Workspace, maximum actuation forces and velocities, power, actuator stiffness, accuracy and transmission behavior are taken into account to investigate strengths and weaknesses of the PKMs. A selection scheme based on possible configurations of translational PKM including different frame configurations is presented. Moreover, an optimization method based on a genetic algorithm is described to determine the geometric parameters of the selected PKM for an exemplary load case and a prescribed workspace. The values of the mentioned criteria are determined for all considered PKM with respect to certain boundary conditions. The distribution and spreading of these values within the prescribed workspace is presented by using box plots for each criterion. Thereby, the performance characteristics of the different structures can be compared directly. The results show that there is no ＂best＂ PKM. Further inquiries such as dynamic or stiffness analysis are necessary to extend the comparison and to finally select a PKM.
文摘基于全球导航卫星系统(global navigation satellite system,GNSS),采用精密单点定位(precise point positioning,PPP)技术的低轨卫星运动学定轨是广泛研究的热点。然而不同低轨卫星搭载星载接收机性能不同,基于其星载GNSS数据的运动学定轨效果也会有所差异。本文首先介绍了GARCE-FO卫星和Swarm卫星及其星载接收机,然后从观测卫星数、伪距多路径以及信号强度对比其数据质量差异,最后基于武汉大学开源的PIRDE PPP-AR软件解算其相应的运动学轨道进行对比。结果表明,GRACE-FO卫星相比Swarm卫星可观测到的GNSS卫星数更多,其各自的伪距多路径分别为0.16~0.19m和0.3~0.44m,并且GRACE-FO卫星的信号强度分布6~9之间,而Swarm卫星L2频率上的信号强度分布在1~7之间。综合来说,Swarm卫星的观测数据质量劣于GRACE-FO。此外,GRACE-FO卫星的模糊度残差表现出良好的近正态分布特性,宽巷模糊度和窄巷模糊度的固定率可达99%和93%,而Swarm卫星的窄巷模糊度残差则分布不规则。与权威机构发布的精密科学轨道对比,GRACE-C在切向、法向和径向3个分量固定解的轨道精度分别为1.39cm、0.98cm和2.59cm,GRACE-D卫星轨道精度与GRACE-C卫星整体一致;Swarm卫星各分量的运动学轨道精度则在3~4 cm左右,相较于GRACE-FO卫星要低1~2 cm。在平差解算时降低参数之间的相关性能有效提高参数估值的精度,使用随机游走估计GRACE-FO卫星的接收机钟差来相较于白噪声在径向分量上有60%左右的提升。此外,欧洲定轨中心(Center for Orbit Determination in Europe,CODE)发布的Swarm卫星运动学轨道以简化动力学解算得到的模糊度作为约束来降低参数相关性,相较于本文解算的运动学轨道在径向分量上也有一定的提升。
