A Novel Linear Model Based on Code Approximation for GNSS/INS Ultra-Tight Integration System

• Published in: Sensors (Basel, Switzerland) Switzerland), 2020-06, Vol.20 (11), p.3192
• Main Authors: Yan, Zhe, Chen, Xiyuan, Tang, Xinhua
• Format: Article
• Language: English
• Subjects: Accuracy; Algorithms; code deviation; GNSS/INS; Inertial navigation; Jacobi matrix method; Jacobian matrix; Navigation systems; nonlinear measurement; ultra-tight integration; Velocity
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s20113192

The superiority of a global navigation satellite system (GNSS)/inertial navigation system (INS) ultra-tight integration navigation system has been widely verified. For those systems with centralized structure based on coherent-accumulation measurements (I/Q), the conversion from I/Q signals to navigation information is implemented by an observation equation. As a result, the model is highly complex and nonlinear, exerting essential influence on system performance. Based on the analysis of previous studies, a novel model and its linearization method are proposed, aiming at the integrity, stability and implicit nonlinear factors. Unlike the one-order precision in the common Jacobian matrix, two-order components are partly reserved in this model, which makes it possible for higher positioning accuracy and better convergence. For the positioning errors caused by ignoring code-loop deviation, a method to approximate code-phase is proposed without introducing new measurements. Consequently, the effect of code error can be significantly reduced, especially when the tracking loops are unstable. In the end, using real-sampled satellite signals, semi-physical experiments are carried out and the effectiveness and superiority of new methods are proved.