Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telesc...Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telescope(TMRT)as an example object,the pointing errors caused by wind loads are investigated using an accelerometer system.First,the resonant frequency range of the antenna structure is used for reference to acquire useful signals through the bandpass filtering method.Then,the direct current(DC)component of these signals is filtered out using the fast discrete Fourier transform method,and the baseline of the acceleration is corrected using the least-squares method.Finally,the acceleration integral is solved approximately using the discrete trapezoidal area method,and the structural vibration displacement of the antenna is determined using a double integral of acceleration.The pointing errors are then obtained based on the displacement relationship between the primary and subreflector surfaces.When the wind speed is 3.2 m/s,the antenna pitch angle is 61.7°and the wind direction angle is 80°,the generated pitch pointing error is 3.05'',and the azimuth pointing error is 1.14''.These results are consistent with those obtained via inclinometer measurements,thus validating the signal processing method and the pointing error calculation method proposed in this paper.The research methods and data analysis results reported here provide a basis for further wind-induced pointing error correction studies.展开更多
针对传统电压源逆变器无模型预测电流控制(model-free predictive current control,MFPCC)方法存在电流纹波大、电流梯度更新停滞以及预测性能易受采样扰动影响的问题。该文提出一种计及采样扰动的三矢量MFPCC方法。在一个控制周期应用...针对传统电压源逆变器无模型预测电流控制(model-free predictive current control,MFPCC)方法存在电流纹波大、电流梯度更新停滞以及预测性能易受采样扰动影响的问题。该文提出一种计及采样扰动的三矢量MFPCC方法。在一个控制周期应用3个基本矢量,并根据价值函数计算矢量作用时间,降低了输出电流纹波;其次,通过建立不同矢量作用下的电流梯度方程组,实现电流梯度数据的实时更新,消除了停滞现象;再次,分析采样扰动对MFPCC的影响,采用扩张状态观测器估计采样扰动以补偿预测电流控制,抑制其对输出电流的影响。最后,通过仿真和实验,对所提方法的有效性进行了验证。展开更多
针对传统永磁同步电机(permanent magnet synchronous motor,PMSM)三矢量模型预测电流控制(three-vector model predictive current control,TV-MPCC)存在开关频率不固定和计算复杂的问题,提出一种固定开关频率TV-MPCC策略。利用前一周...针对传统永磁同步电机(permanent magnet synchronous motor,PMSM)三矢量模型预测电流控制(three-vector model predictive current control,TV-MPCC)存在开关频率不固定和计算复杂的问题,提出一种固定开关频率TV-MPCC策略。利用前一周期的零电压矢量和参考电压矢量所在扇区来快速筛选所需最优电压矢量和次优电压矢量,避免了无效枚举计算,从而降低了开关频率和计算复杂度。引入系统d和q轴电流差参数,计算各电压矢量的作用时间,确保电压矢量作用时间恒大于零和开关频率固定。以三相两电平电压型逆变器驱动的表贴式PMSM为被控对象,通过仿真和实验对传统TV-MPCC策略和所提三矢量固定开关频率模型预测电流控制策略进行对比研究,仿真和实验结果表明,所提策略在保证系统稳态和动态性能的基础上,在固定和降低开关频率的同时,降低了计算复杂度。展开更多
基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采...基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采用车身结构材料的弹塑性本构模型。前防撞梁碰撞冲击数值算例结果表明,MPM可以保证求解精度,同时矢量化技术可以大幅提高求解效率。展开更多
电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Mod...电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Model predictive direct power control,MPDPC)对传统控制策略进行改进。首先建立了三相PWM整流器的数学模型,给出了每个采样周期内的功率变化率,并推导出相邻采样周期之间的功率关系,然后给出基于单矢量的模型预测直接功率控制策略,提出了基于双矢量的模型预测直接功率控制策略,并优选出两个电流矢量,计算在一个采样周期内的作用时间,并对其进行修正。最后,在Matlab/Simulink仿真软件验证了所提控制策略的可行性和有效性。展开更多
基金provided by the TMRT operators during the observations.This work was supported by the National Key Basic Research and Development Program(2018YFA0404702)the National Natural Science Foundation of China(U1631114,11873015,and 11203062)+2 种基金the CAS Key Technology Talent Program,the Knowledge Innovation Program of CAS(KJCX1-YW-18)the Scientific Program of Shanghai Municipality(08DZ1160100)the Key Laboratory for Radio Astronomy of CAS,the Key Laboratory of Planetary Sciences of CAS,and the CAS Scholarship.
文摘Wind loads have instantaneity and turbulence characteristics that will lead to pointing errors in antenna structures,and these errors cannot be ignored in high-frequency observations.Using the Tianma 65 m radio telescope(TMRT)as an example object,the pointing errors caused by wind loads are investigated using an accelerometer system.First,the resonant frequency range of the antenna structure is used for reference to acquire useful signals through the bandpass filtering method.Then,the direct current(DC)component of these signals is filtered out using the fast discrete Fourier transform method,and the baseline of the acceleration is corrected using the least-squares method.Finally,the acceleration integral is solved approximately using the discrete trapezoidal area method,and the structural vibration displacement of the antenna is determined using a double integral of acceleration.The pointing errors are then obtained based on the displacement relationship between the primary and subreflector surfaces.When the wind speed is 3.2 m/s,the antenna pitch angle is 61.7°and the wind direction angle is 80°,the generated pitch pointing error is 3.05'',and the azimuth pointing error is 1.14''.These results are consistent with those obtained via inclinometer measurements,thus validating the signal processing method and the pointing error calculation method proposed in this paper.The research methods and data analysis results reported here provide a basis for further wind-induced pointing error correction studies.
文摘针对传统电压源逆变器无模型预测电流控制(model-free predictive current control,MFPCC)方法存在电流纹波大、电流梯度更新停滞以及预测性能易受采样扰动影响的问题。该文提出一种计及采样扰动的三矢量MFPCC方法。在一个控制周期应用3个基本矢量,并根据价值函数计算矢量作用时间,降低了输出电流纹波;其次,通过建立不同矢量作用下的电流梯度方程组,实现电流梯度数据的实时更新,消除了停滞现象;再次,分析采样扰动对MFPCC的影响,采用扩张状态观测器估计采样扰动以补偿预测电流控制,抑制其对输出电流的影响。最后,通过仿真和实验,对所提方法的有效性进行了验证。
文摘针对传统永磁同步电机(permanent magnet synchronous motor,PMSM)三矢量模型预测电流控制(three-vector model predictive current control,TV-MPCC)存在开关频率不固定和计算复杂的问题,提出一种固定开关频率TV-MPCC策略。利用前一周期的零电压矢量和参考电压矢量所在扇区来快速筛选所需最优电压矢量和次优电压矢量,避免了无效枚举计算,从而降低了开关频率和计算复杂度。引入系统d和q轴电流差参数,计算各电压矢量的作用时间,确保电压矢量作用时间恒大于零和开关频率固定。以三相两电平电压型逆变器驱动的表贴式PMSM为被控对象,通过仿真和实验对传统TV-MPCC策略和所提三矢量固定开关频率模型预测电流控制策略进行对比研究,仿真和实验结果表明,所提策略在保证系统稳态和动态性能的基础上,在固定和降低开关频率的同时,降低了计算复杂度。
文摘基于MATLAB矢量化的物质点法(material point method,MPM)框架,分析车身前防撞梁的碰撞冲击问题。MPM在每一迭代步将物理参数在物质点和背景网格间相互映射,使用MATLAB矢量化框架可以使用户在快速入门的同时保证求解效率,其应力更新采用车身结构材料的弹塑性本构模型。前防撞梁碰撞冲击数值算例结果表明,MPM可以保证求解精度,同时矢量化技术可以大幅提高求解效率。
文摘电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Model predictive direct power control,MPDPC)对传统控制策略进行改进。首先建立了三相PWM整流器的数学模型,给出了每个采样周期内的功率变化率,并推导出相邻采样周期之间的功率关系,然后给出基于单矢量的模型预测直接功率控制策略,提出了基于双矢量的模型预测直接功率控制策略,并优选出两个电流矢量,计算在一个采样周期内的作用时间,并对其进行修正。最后,在Matlab/Simulink仿真软件验证了所提控制策略的可行性和有效性。
