Design of a Constrained Extended State Observer for Practical Implementation on an INS/GNSS Integrated Navigation System

This paper addresses the design and practical implementation of a constrained extended state observer for integration between an inertial navigation system (INS) and a global navigation satellite system (GNSS) navigation system in the presence of model uncertainties and inertial sensor errors. The use of physical constraints in the observer design can achieve an accurate and reliable model for the inertial navigation system during GNSS outages. The proposed method provides an estimate of this variable alongside the state variables of the inertial navigation system by considering the term including model uncertainties and inertial sensor errors as a new state variable. Additionally, the use of motion and environmental constraints in the proposed observer, including non-holonomic constraints and altitude constraints, improves estimation accuracy, reduces error accumulation, and increases the dynamic stability of the estimates. The performance of the proposed observer is evaluated through vehicle tests in a real-world test environment. The results indicate that the model uncertainties and inertial sensor errors in the inertial navigation system can be estimated in real-time. Thus, the designed observer can provide reliable estimates of the state variables by using GNSS information during its availability and utilizing physical constraints during GNSS outages. Furthermore, the proposed algorithm is fast due to its low computational load, making it suitable for practical implementation.