The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the t...The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the tracking loop.Since the frequency step is usually 500 Hz or larger,the Doppler shift estimation accuracy cannot guarantee that satellite signals are brought into a stable tracking state.The straightforward solutions consist in increasing the sampling time and using zero-padding to improve the frequency resolution of the FFT.However,these solutions intensify the complexity and amount of computation.The contradiction between the acquisition accuracy and the computational load leads us to research for a more simple and effective algorithm,which achieves fine acquisition by a look-up table.After coarse acquisition using the parallel frequency acquisition(PFA)algorithm,the proposed algorithm optimizes the Doppler shift estimation through the look-up table method based on the FFT results to improve the acquisition accuracy of the Doppler shift with a minimal additional computing load.When the Doppler shift is within the queryable range of the table,the proposed algorithm can improve the Doppler shift estimation accuracy to 50 Hz for the BeiDou B1I signal.展开更多
针对目前企业内部定期对电磁流量计进行期间核查时,核查方法自动化程度低,核查周期制定不合理的问题,通过图像识别方式采集电磁流量计的累积流量数据,采用标准表法对电磁流量计进行期间核查;通过线性维纳退化模型对电磁流量计的核查数...针对目前企业内部定期对电磁流量计进行期间核查时,核查方法自动化程度低,核查周期制定不合理的问题,通过图像识别方式采集电磁流量计的累积流量数据,采用标准表法对电磁流量计进行期间核查;通过线性维纳退化模型对电磁流量计的核查数据进行处理,智能预测电磁流量计的期间核查周期;基于该核查方法与周期预测方法研制一套可移动式核查装置,对电磁流量计进行原位核查。核查装置扩展不确定度为0.08%(k=2),满足技术指标0.15%(k=2)的要求;使用核查装置对E+H Proline Promag H 500进行核查实验,最大示值误差为0.2%,与最大允许误差±0.5%相比,满足性能指标要求;使用线性维纳退化模型对E+H Proline Promag H 500进行核查周期预测,预测核查周期的均方根误差为6.04 d。该核查方法与周期预测方法均具有良好的可靠性,可用于对电磁流量计的期间核查。展开更多
基金the Open Project of State Key Laboratory of Automotive Simulation and Control,Jilin University(20161108)the National Natural Science Foundation of China(51505221)the Fundamental Research Funds for the Central Universities(NS2019022).
文摘The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the tracking loop.Since the frequency step is usually 500 Hz or larger,the Doppler shift estimation accuracy cannot guarantee that satellite signals are brought into a stable tracking state.The straightforward solutions consist in increasing the sampling time and using zero-padding to improve the frequency resolution of the FFT.However,these solutions intensify the complexity and amount of computation.The contradiction between the acquisition accuracy and the computational load leads us to research for a more simple and effective algorithm,which achieves fine acquisition by a look-up table.After coarse acquisition using the parallel frequency acquisition(PFA)algorithm,the proposed algorithm optimizes the Doppler shift estimation through the look-up table method based on the FFT results to improve the acquisition accuracy of the Doppler shift with a minimal additional computing load.When the Doppler shift is within the queryable range of the table,the proposed algorithm can improve the Doppler shift estimation accuracy to 50 Hz for the BeiDou B1I signal.
文摘针对目前企业内部定期对电磁流量计进行期间核查时,核查方法自动化程度低,核查周期制定不合理的问题,通过图像识别方式采集电磁流量计的累积流量数据,采用标准表法对电磁流量计进行期间核查;通过线性维纳退化模型对电磁流量计的核查数据进行处理,智能预测电磁流量计的期间核查周期;基于该核查方法与周期预测方法研制一套可移动式核查装置,对电磁流量计进行原位核查。核查装置扩展不确定度为0.08%(k=2),满足技术指标0.15%(k=2)的要求;使用核查装置对E+H Proline Promag H 500进行核查实验,最大示值误差为0.2%,与最大允许误差±0.5%相比,满足性能指标要求;使用线性维纳退化模型对E+H Proline Promag H 500进行核查周期预测,预测核查周期的均方根误差为6.04 d。该核查方法与周期预测方法均具有良好的可靠性,可用于对电磁流量计的期间核查。
