在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通...在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通过电感和变压器分别调节换能器电阻和电抗,实现电路的精确匹配,以提高超声换能器阻抗匹配的精度和稳定性,并给出了理想的匹配条件和匹配参数。利用匝数可调的变压器和电感制作了超声换能器的匹配电路,对20.8 k Hz的变幅杆换能器进行了阻抗匹配的实验测量,结果证明这种"电感-变压器"阻抗匹配模型在谐振频率附近具有较小的电抗变化范围、较低的电阻变化率和较高的电抗调节精度,在超声换能器的自动阻抗匹配中具有良好的应用前景。展开更多
The accurate weighting of pseudorange observations is important to improve the convergence time and positioning quality of Precise Point Positioning(PPP).Currently,the weight of a pseudorange observation is mainly det...The accurate weighting of pseudorange observations is important to improve the convergence time and positioning quality of Precise Point Positioning(PPP).Currently,the weight of a pseudorange observation is mainly determined with empirical stochastic models.However,in a complex environment,due to the inability to adapt for the dynamic changes of the user environment,the empirical stochastic models usually cannot reflect the real error level of pseudorange observations.To address this problem,a resilient adjustment method to weigh pseudorange observations is proposed,which constructs the real-time estimation and inflation model for the variance of pseudorange multipath error and measurement noise to replace the empirical stochastic model to determine the weights of pseudorange observations.A set of static and dynamic Global Positioning System(GPS)test data are used to verify the effectiveness of the proposed method.The test results indicate that the proposed real-time estimation model can provide a better representation of the pseudorange accuracy,and the positioning performance of PPP using the real-time estimation model is better than that with the empirical stochastic model.Compared with the optimal empirical stochastic model,the positioning accuracy of PPP with the real-time estimation model is improved by at least 20%,and the convergence time is reduced by at least 50%.展开更多
文摘在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通过电感和变压器分别调节换能器电阻和电抗,实现电路的精确匹配,以提高超声换能器阻抗匹配的精度和稳定性,并给出了理想的匹配条件和匹配参数。利用匝数可调的变压器和电感制作了超声换能器的匹配电路,对20.8 k Hz的变幅杆换能器进行了阻抗匹配的实验测量,结果证明这种"电感-变压器"阻抗匹配模型在谐振频率附近具有较小的电抗变化范围、较低的电阻变化率和较高的电抗调节精度,在超声换能器的自动阻抗匹配中具有良好的应用前景。
基金National Key Research and Development Program of China(Grant No.2020YFB0505804)Fundamental Research Funds for the Central Universities(Grant No.56XAA22055)+1 种基金National Natural Science Foundation of China(Grant No.41874034)Beijing Natural Science Foundation(Grant No.4202041).
文摘The accurate weighting of pseudorange observations is important to improve the convergence time and positioning quality of Precise Point Positioning(PPP).Currently,the weight of a pseudorange observation is mainly determined with empirical stochastic models.However,in a complex environment,due to the inability to adapt for the dynamic changes of the user environment,the empirical stochastic models usually cannot reflect the real error level of pseudorange observations.To address this problem,a resilient adjustment method to weigh pseudorange observations is proposed,which constructs the real-time estimation and inflation model for the variance of pseudorange multipath error and measurement noise to replace the empirical stochastic model to determine the weights of pseudorange observations.A set of static and dynamic Global Positioning System(GPS)test data are used to verify the effectiveness of the proposed method.The test results indicate that the proposed real-time estimation model can provide a better representation of the pseudorange accuracy,and the positioning performance of PPP using the real-time estimation model is better than that with the empirical stochastic model.Compared with the optimal empirical stochastic model,the positioning accuracy of PPP with the real-time estimation model is improved by at least 20%,and the convergence time is reduced by at least 50%.
