Velocity updating based on two auxiliary frames

Abstract

The conventional velocity updating algorithms are sufficient for the low and medium-accuracy strapdown INS. However, the accuracy of conventional algorithms is not sufficient for a high-accuracy strapdown INS and the high-dynamic environment. To solve this issue, a new velocity updating algorithm is proposed in this paper. It employs two auxiliary frames to reduce the rate of change in direction of the specific force and angular rate vectors. The first slewing frame slews at a constant rate about a fixed axis in the vehicle frame and the second slewing frame slews at a constant rate about a fixed axis in the first slewing frame. With the proper choice of slew rates, the angular rate and specific force vectors of the second slewing frame changes direction more slowly than that of the vehicle frame. Integrating of the transformed specific force vector in the second slewing frame and then translating it to the navigation frame could determine the updated velocity. The velocity updating algorithm presented in this paper does not involve sculling correction. Simulation and trial results demonstrated that this algorithm has a higher accuracy than the conventional algorithms. This algorithm plays an important role in the high-dynamic environment and a high-accuracy strapdown INS.