Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the exp...Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the experimental module manipulator(EMM)in the Chinese Space Station Remote Manipulator System.However,finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult.This study proposes a high-precision,semi-analytical inverse method for EMMs.Firstly,the analytical inverse kinematic solution is established based on joint angle parameterization.Secondly,the analytical inverse kinematic solution for a non-offset spherical-roll-spherical(SRS)redundant manipulator is derived based on arm angle parameterization.The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator.Thirdly,the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization.After selecting the stride and termination condition,the precise inverse solution is computed for the EMM based on arm angle parameterization.Lastly,case solutions confirm that this method has high precision,and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.展开更多
生成树算法的网桥协议STP(Spanning Tree Protocol)它通过自动形成生成树使得在网络中一个透明的网桥以动态方式在复杂的网络拓扑结构中沿环状工作。网络中的环路由网桥之间通过交换配置桥协议数据单元消息来进行监测,通过关闭选择的网...生成树算法的网桥协议STP(Spanning Tree Protocol)它通过自动形成生成树使得在网络中一个透明的网桥以动态方式在复杂的网络拓扑结构中沿环状工作。网络中的环路由网桥之间通过交换配置桥协议数据单元消息来进行监测,通过关闭选择的网桥接口的方式破除环路。局域网通常由多种网络设备相互连接形成,我们只有消除网络中的环路才能有效降低广播风暴的发生,也就是说网络中的链路应组成树形的无环路结构,使用STP(生成树协议)就可以解决这样的问题。展开更多
为减小卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer,TWSTFT)中的周日效应,利用北斗共视链路没有周日效应的特点,通过Vondrak-Cepek组合滤波方法对中国科学院国家授时中心(National Time Service Center,NTSC)、德...为减小卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer,TWSTFT)中的周日效应,利用北斗共视链路没有周日效应的特点,通过Vondrak-Cepek组合滤波方法对中国科学院国家授时中心(National Time Service Center,NTSC)、德国物理技术研究院(Physikalisch-Technische Bundesanstalt,PTB)以及中国计量科学研究院(National Institute of Metrology,NIM)间的北斗共视时间比对结果分别与硬件卫星时间和距离测量设备(SAtellite Time and Ranging Equipment,SATRE)TWSTFT和软件接收机(Software-Defined Radio,SDR)TWSTFT结果进行了融合处理。采用时间偏差和幅值频谱两个指标以及GPS精密单点定位(Precise Point Positioning,PPP)时间比对分别对融合结果进行内外符合评估。结果表明,经过Vondrak-Cepek滤波的融合结果中周日效应基本消失,其与GPS PPP链路差值结果的绝对值保持在链路校准的不确定度范围内。对于长基线NTSC-PTB链路,融合结果1 d的时间偏差稳定度对SATRE和SDR TWSTFT的增益因子分别为1.85和1.81;对于短基线NTSC-NIM链路,融合结果对SATRE和SDR TWSTFT的增益因子分别为1.69和1.59。融合结果的短期稳定度显著提高。展开更多
CCSDS(Consultative Committee for Space Data Systems,空间数据系统咨询委员会)SLE(Space Link Extension,空间链路拓展)网络协议体系模型中,一个服务实例只支持建立一个物理通信链路,造成上层应用与下层链路耦合过强,存在一定的安全...CCSDS(Consultative Committee for Space Data Systems,空间数据系统咨询委员会)SLE(Space Link Extension,空间链路拓展)网络协议体系模型中,一个服务实例只支持建立一个物理通信链路,造成上层应用与下层链路耦合过强,存在一定的安全隐患。针对此问题,设计了基于冗余连接机制的SLE网络协议体系模型,该模型在现有的SLE网络协议体系模型中增加了逻辑连接层,支持单一服务实例同时使用多个物理链路进行空间数据传输,可根据多连接状态重新设计TML(Transport Mapping Layer,传输映射层)状态变换关系以及数据传输模式。该模型能够兼容现有的SLE网络传输体系模型,提高SLE服务的可靠性。展开更多
基金This work was supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.51521003)the Major Research Plan of National Natural Science Foundation of China(Grant No.91848202).
文摘Seven-degree-of-freedom redundant manipulators with link offset have many advantages,including obvious geometric significance and suitability for configuration control.Their configuration is similar to that of the experimental module manipulator(EMM)in the Chinese Space Station Remote Manipulator System.However,finding the analytical solution of an EMM on the basis of arm angle parameterization is difficult.This study proposes a high-precision,semi-analytical inverse method for EMMs.Firstly,the analytical inverse kinematic solution is established based on joint angle parameterization.Secondly,the analytical inverse kinematic solution for a non-offset spherical-roll-spherical(SRS)redundant manipulator is derived based on arm angle parameterization.The approximate solution of the EMM is calculated in accordance with the relationship between the joint angles of the EMM and the SRS manipulator.Thirdly,the error is corrected using a numerical method through the analytical inverse solution based on joint angle parameterization.After selecting the stride and termination condition,the precise inverse solution is computed for the EMM based on arm angle parameterization.Lastly,case solutions confirm that this method has high precision,and the arm angle parameterization method is superior to the joint angle parameterization method in terms of parameter selection.
文摘生成树算法的网桥协议STP(Spanning Tree Protocol)它通过自动形成生成树使得在网络中一个透明的网桥以动态方式在复杂的网络拓扑结构中沿环状工作。网络中的环路由网桥之间通过交换配置桥协议数据单元消息来进行监测,通过关闭选择的网桥接口的方式破除环路。局域网通常由多种网络设备相互连接形成,我们只有消除网络中的环路才能有效降低广播风暴的发生,也就是说网络中的链路应组成树形的无环路结构,使用STP(生成树协议)就可以解决这样的问题。
文摘为减小卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer,TWSTFT)中的周日效应,利用北斗共视链路没有周日效应的特点,通过Vondrak-Cepek组合滤波方法对中国科学院国家授时中心(National Time Service Center,NTSC)、德国物理技术研究院(Physikalisch-Technische Bundesanstalt,PTB)以及中国计量科学研究院(National Institute of Metrology,NIM)间的北斗共视时间比对结果分别与硬件卫星时间和距离测量设备(SAtellite Time and Ranging Equipment,SATRE)TWSTFT和软件接收机(Software-Defined Radio,SDR)TWSTFT结果进行了融合处理。采用时间偏差和幅值频谱两个指标以及GPS精密单点定位(Precise Point Positioning,PPP)时间比对分别对融合结果进行内外符合评估。结果表明,经过Vondrak-Cepek滤波的融合结果中周日效应基本消失,其与GPS PPP链路差值结果的绝对值保持在链路校准的不确定度范围内。对于长基线NTSC-PTB链路,融合结果1 d的时间偏差稳定度对SATRE和SDR TWSTFT的增益因子分别为1.85和1.81;对于短基线NTSC-NIM链路,融合结果对SATRE和SDR TWSTFT的增益因子分别为1.69和1.59。融合结果的短期稳定度显著提高。
文摘CCSDS(Consultative Committee for Space Data Systems,空间数据系统咨询委员会)SLE(Space Link Extension,空间链路拓展)网络协议体系模型中,一个服务实例只支持建立一个物理通信链路,造成上层应用与下层链路耦合过强,存在一定的安全隐患。针对此问题,设计了基于冗余连接机制的SLE网络协议体系模型,该模型在现有的SLE网络协议体系模型中增加了逻辑连接层,支持单一服务实例同时使用多个物理链路进行空间数据传输,可根据多连接状态重新设计TML(Transport Mapping Layer,传输映射层)状态变换关系以及数据传输模式。该模型能够兼容现有的SLE网络传输体系模型,提高SLE服务的可靠性。
