An attitude navigation system based on the GPS

الملخص EN

In this paper, the use of multi-GPS receiver to estimate the parameters of attitude (orientation) of a platform is developed.

The GPS receiver has two measurements; pseudorange and carrier phase.

The latter is highly accurate (sub centimeter-level).

Therefore, it is used to give precise attitude parameters.

But the carrier phase has one problem; an initial integer ambiguity must be resolved first. Without resolution of this integer, the carrier phase is meaningless.

Therefore, the attitude determination technique based on the carrier phase observable of the GPS involves two steps; integer ambiguity resolution and attitude estimation.

Here, two methods are used for attitude estimation; first, Single-point method that is based on the least square approach is developed using the quaternion representation.

Second, Eigenproblem algorithm that is used to minimize a quartic quaternion-based cost function.

In order to resolve the integer ambiguity, an attitude-independent algorithm is developed.

This algorithm first incorporates an instantaneous integer search to significantly reduce the search space using a geometric inequality.

Then, a batch-type loss function is used to check the remaining integers in order to determine the optimal integer.

The results show that the Single-point method is more accurate (with RMS 0.137, 0.079 and 0.197 degree in yaw, pitch and roll respectively), and it convergences exponentially to the correct solution.

The Eigenproblem may diverge when the initial quaternion is far.