Numerical and experimental study of an algorithm of attitude for a strap-down inertial system

Two numerical algorithms are presented here: the integration of the Poisson equation of attitude and the calculation of the angles from the elements of the matrix of attitude. The method here suggested lies in the use of a fast algorithm of Wilcox type in which the errors of commutation are eliminated by the use of a numerical artifice implemented in a data acquisition card: information on the angular velocity is given on only one channel among the three channels of the chart (the two other channels are put at zero) during a step of calculation. The numerical simulations are performed and validated by use of the Wilcox integration method which implies errors of commutation, with various orders of truncation, and by the integration method with an algorithm with two rates of calculation. By use of a strap-down inertial system and the Matlab software, real time experimental tests are carried out to calculate the best alternatives of the algorithm of integration resulted from the numerical simulations.