Читать книгу Global Navigation Satellite Systems, Inertial Navigation, and Integration - Mohinder S. Grewal - Страница 135

These are momentum wheel gyroscopes whose spin axes are unconstrained, such as they are for Foucault's gimbaled gyroscope or electrostatic gyroscopes. In either case, the direction of the spin axis serves as an inertial reference – like a star. Two of these with quasi‐orthogonal spin axes provide a complete inertial reference system. The only attitude propagation required in this case is to compensate for the spin axis drifts due to bearing torques and rotor axial mass unbalance (an acceleration‐sensitive effect). The different coordinate systems involved are illustrated in Figure 3.18.

Figure 3.18 Coordinates for strapdown navigation with whole‐angle gyroscopes.

Figure 3.19 Attitude representation formats and MATLAB® transformations.