The Research Of SINS Velocity Algorithm Based On The Virtual Slewing Coordinate System

As a crucial part of the strapdown inertial navigation algorithm, strapdown inertial navigation system’s velocity algorithm gives the vehicle’s velocity on each axis of the platform coordinate system (the navigation coordinate system), and is the input of position algorithm for further calculation of vehicle position. And it involves in angular rate’s calculation to ensure the updating accuracy of the mathematics platform. Today, the velocity algorithm of strapdown inertial navigation system mainly is the sculling compensation algorithm, but the algorithm has two shortcomings have not been given: Optimization of sculling algorithm is done in the typical sculling environment, and this kind of environment do not have a complete applicability, then it will lose its optimality under the realistic environment; When designing the existing velocity algorithm they thought that IMU (inertial measurement units) and preprocessing filter’s transfer function were ideal, and the signal input which be used is the movement parameters of carrier without considering the influence of the no-ideal of IMU and preprocessing filter transfer function on the engineering’s velocity algorithm.This paper will break out the design idea of existing algorithm, and constructs the virtual slewing coordinate system. The virtual slewing frame follows the angular rate and force of body frame in the inertial space, and overall consider the force vector integral term on the coordinate system. Because the force vector is connected with the coordinate system, its projection on virtual slewing frame will be constant; The slewing rate of virtual slewing coordinate system relative to the reference frame is far less than the body coordinate system.Namely comparing the coordinate system and the existing algorithm, the direction cosine matrix’s commutative error will decrease sharply. Firstly, we will design a velocity algorithm based on the constant slewing coordinate system in a typical single slewing environment. Due to the angular rate be constant, we expect that it can realize the no error velocity of the algorithm; then base on the typical single slewing environment, we will design a time-varying slewing motion environment, including time-varying single slewing and double slewing movement environment, they not only consider the angular rate’s and force vector’s rotation,time-varying single slewing motion environment also think its slewing angular rate size be changed over time, the double slewing motion environment given its change direction. The two kinds of time-varying slewing environment can give more universal applicable test inputs than the typical slewing environment, which solve the lack of universality and algorithm optimization problem what the existing typical sculling environment has; Finally we consider the transfer function’s influence of IMU and preprocessing filter on IMU output signals,getting IMU output signals in the realistic environment, and based on this signals we will finish the design work. This work will avoid velocity error caused by ignoring the transfer function no-ideal (amplitude frequency and phase frequency characteristics). After the completion of the above three researches, we will do the mathematical simulation in the corresponding input environment,comparing with the existing algorithm’s velocity accuracy,and demonstrate velocity accuracy, optimality and universality of the algorithms which this paper designed,Above all, the research worked on this paper will solve the problems of the existing algorithm,and form a set of higher accuracy,optimality and more universal applicability strapdown velocity algorithm, then effectively improve the performance of SINS.