Global positioning system (GPS) technology is well suited for attitude determination. However, in land vehicle application, low-cost single frequency GPS receivers which have low measurement quality are often used, and external factors such as multipath and low satellite visibility in the densely built-up urban environment further degrade the quality of the GPS measurements. Due to the low-quality receivers used and the challenging urban environment, the success rate of the single epoch ambiguity resolution for dynamic attitude determination is usually quite low. In this paper, a micro-electro-mechanical system (MEMS)—inertial navigation system (INS)-aided ambiguity resolution method is proposed to improve the GPS attitude determination performance, which is particularly suitable for land vehicle attitude determination. First, the INS calculated baseline vector is augmented with the GPS carrier phase and code measurements. This improves the ambiguity dilution of precision (ADOP), resulting in better quality of the unconstrained float solution. Second, the undesirable float solutions caused by large measurement errors are further filtered and replaced using the INS-aided ambiguity function method (AFM). The fixed solutions are then obtained by the constrained least squares ambiguity decorrelation (CLAMBDA) algorithm. Finally, the GPS/MEMS-INS integration is realized by the use of a Kalman filter. Theoretical analysis of the ADOP is given and experimental results demonstrate that our proposed method can significantly improve the quality of the float ambiguity solution, leading to high success rate and better accuracy of attitude determination.
GPS compasses equipped with short baselines can provide precise heading and elevation information for land vehicles. Most recent research in this area has focused on developing single-frequency, single-epoch ambiguity resolution, as the ambiguity resolution in a single epoch can guarantee total independence from carrier phase slips and lock losses. The reliability of single-frequency, single-epoch ambiguity resolution, however, are often insufficient for actual applications due to the weak baseline model. For land vehicle applications, baseline elevation can also be measured by inclinometer, which provides an important constraint that can be exploited to directly assist the ambiguity resolution process. In this study, we developed an innovative method that fully integrates MEMS-based inclinometer measurements into single-difference GPS observation equations and obtains the fixed baseline solution via weighted constrained integer least squares. We then explored the performance and effectiveness of the proposed method by building an integrated GPS/inclinometer compass system (IGICS) with low-cost GPS receivers (U-Blox LEA-6T) and a MEMS-based inclinometer (SCA-100T). Both actual static and dynamic experiments demonstrated that our method is capable of successfully fixing the set of integer ambiguities to the correct value for land vehicles equipped with very short baselines. The proposed method is also more easily implemented than the traditional augmenting scheme with rate gyros and IMU, as evidenced by a comparative experiment conducted using three approaches: (1) the new method; (2) horizontal constraint without inclinometer measurements; and (3) exploiting inclinometer measurements without imposing horizontal constraints.
POEMS syndrome is a rare clonal plasma cell disease associated with multisystem involvement. We reported a case of 48‐year‐old woman with large volume of exudative ascites with an increased level of λ‐light chain and hepatosplenomegaly. The patient was treated with thalidomide and dexamethasone and showed a good clinical response.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.