Velocity/Position Integration Formula (I): Application to In-flight Coarse Alignment
This addresses the difficulty of in-flight alignment for airborne navigation systems, offering a practical solution without prior attitude information, though it appears incremental as it builds on existing alignment techniques.
The paper tackles the problem of in-flight coarse alignment for airborne INS/GPS systems by proposing an optimization-based approach using GPS position/velocity inputs, achieving initial heading accuracy up to one degree in ten seconds in simulations and flight tests.
The in-flight alignment is a critical stage for airborne INS/GPS applications. The alignment task is usually carried out by the Kalman filtering technique that necessitates a good initial attitude to obtain satisfying performance. Due to the airborne dynamics, the in-flight alignment is much difficult than alignment on the ground. This paper proposes an optimization-based coarse alignment approach using GPS position/velocity as input, founded on the newly-derived velocity/position integration formulae. Simulation and flight test results show that, with the GPS lever arm well handled, it is potentially able to yield the initial heading up to one degree accuracy in ten seconds. It can serve as a nice coarse in-flight alignment without any prior attitude information for the subsequent fine Kalman alignment. The approach can also be applied to other applications that require aligning the INS on the run.