Weighted-Least-Square Method for GPS Positioning Using Genetic-Algorithms-Optimized Fuzzy Controller
Date Issued
2005
Date
2005
Author(s)
Lin, Che-Chung
DOI
en-US
Abstract
The positioning accuracy of the GPS receiver is essential to users. During positioning, several factors are related to positioning accuracy. NDSV (Normalized Dilution of Precision Slackness Value) proposed here is derived from DOP (Dilution of Precision) and represents the relationship of geometric error to a single satellite. There are tradeoffs among NDSV, SNR and elevation angle to positioning error. If the number of observed satellites is above four, the WLS (Weighted-Least-Square) method which considers three factors (NDSV, SNR, elevation angle) to determine the weighting of the measurement of each satellite through fuzzy controller is applied to enhance the positioning accuracy.
However, the fuzzy controller is difficult to be optimized through trial-and-error method. To solve this problem, we proposed a new approach to design fuzzy controller in three stages (membership functions (mfs), the number of mfs, rules) via GAs (Genetic Algorithms) without violating the common design antecedent of mfs. At the same time, the number of mfs is optimized and optimally reduced through fitness function design.
The optimized fuzzy controller can be used to determine position and velocity through WLS method simultaneously. Furthermore, we can include the more precise estimated position and velocity from WLS into Kalman filter as measurement to further improve positioning accuracy.
The numerical results show that the positioning using WLS method is improved in comparison with LS method. The Kalman filter which includes the estimated position and velocity from WLS as measurements can further improved the positioning accuracy in comparison with including the estimated position and velocity from LS. Due to its performance and simplified structure, the trained fuzzy controller may be potentially used on a low-cost GPS receiver.
Subjects
全球定位系統
權重最小平方法
遺傳演算法
最佳化
模糊控制器
GPS
Weighted-Least-Square Method
Genetic Algorithms
Optimization
Fuzzy controller
Type
thesis
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