针对换相失败影响因素分析已经取得一些成果,但故障清除时刻(故障分闸角)对换相失败的影响有待进一步研究。首先基于换相失败过程分析过零点偏移角对关断角的影响;其次基于换相电压时间面积法分析不同故障合闸角对逆变器首次换相失败的...针对换相失败影响因素分析已经取得一些成果,但故障清除时刻(故障分闸角)对换相失败的影响有待进一步研究。首先基于换相失败过程分析过零点偏移角对关断角的影响;其次基于换相电压时间面积法分析不同故障合闸角对逆变器首次换相失败的影响,并进一步分析故障分闸角及过零点偏移角对后续换相失败的影响,发现故障在换相过程中清除引发后续换相失败风险最大;最后以单相接地故障为例,基于PSCAD/EMTDC中的(conseil international des grands reseaux electriques,CIGRE)模型的不同故障合闸角与分闸角的仿真测试结果验证了理论分析的正确性。展开更多
针对频控阵(frequency diverse array,FDA)在对与目标位置相近的平台外干扰进行抑制时,传统FDA与非线性频偏结合不能实现距离-角度去耦合、对数递增FDA主瓣展宽较大和汉明窗加权FDA距离维旁瓣过高的问题,在充分研究汉明窗加权的线性FDA(...针对频控阵(frequency diverse array,FDA)在对与目标位置相近的平台外干扰进行抑制时,传统FDA与非线性频偏结合不能实现距离-角度去耦合、对数递增FDA主瓣展宽较大和汉明窗加权FDA距离维旁瓣过高的问题,在充分研究汉明窗加权的线性FDA(Hamming linear FDA,HL-FDA)方案的基础上,对4种频偏方案的性能进行了分析,提出采用FDA多输入多输出结构代替传统的一维均匀线性FDA结构,通过结合最小方差无失真响应(minimum variance distortion free respinse,MVDR)准则,将HL-FDA应用到MVDR自适应波束形成层面,对平台外干扰进行抑制。仿真验证了HL-FDA在结合MVDR自适应波束形成算法后能有效地对抗距离-角度二维平台外干扰。展开更多
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
文摘针对换相失败影响因素分析已经取得一些成果,但故障清除时刻(故障分闸角)对换相失败的影响有待进一步研究。首先基于换相失败过程分析过零点偏移角对关断角的影响;其次基于换相电压时间面积法分析不同故障合闸角对逆变器首次换相失败的影响,并进一步分析故障分闸角及过零点偏移角对后续换相失败的影响,发现故障在换相过程中清除引发后续换相失败风险最大;最后以单相接地故障为例,基于PSCAD/EMTDC中的(conseil international des grands reseaux electriques,CIGRE)模型的不同故障合闸角与分闸角的仿真测试结果验证了理论分析的正确性。
文摘针对频控阵(frequency diverse array,FDA)在对与目标位置相近的平台外干扰进行抑制时,传统FDA与非线性频偏结合不能实现距离-角度去耦合、对数递增FDA主瓣展宽较大和汉明窗加权FDA距离维旁瓣过高的问题,在充分研究汉明窗加权的线性FDA(Hamming linear FDA,HL-FDA)方案的基础上,对4种频偏方案的性能进行了分析,提出采用FDA多输入多输出结构代替传统的一维均匀线性FDA结构,通过结合最小方差无失真响应(minimum variance distortion free respinse,MVDR)准则,将HL-FDA应用到MVDR自适应波束形成层面,对平台外干扰进行抑制。仿真验证了HL-FDA在结合MVDR自适应波束形成算法后能有效地对抗距离-角度二维平台外干扰。
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.
