一种适用于光纤捷联罗经寻北的新算法

New north finding algorithm for strapdown compass based on FOG

舰船的摇摆使陀螺仪无法测出地球自转角速度(Ω),进而光纤捷联罗经系统无法根据陀螺仪和加速度计的输出直接计算出载体航向.针对这一问题,提出了一种寻北新算法.该算法以"固定"的参考系——惯性坐标系为参考基准,建立了过渡惯性坐标系和初始时刻捷联惯组惯性坐标系,利用加速度计敏感重力加速度在惯性坐标系中的投影计算出Ω的空间指向,得到地理真北.光纤捷联罗经系统寻北算法的实现分解为3个步骤:建立初始时刻捷联惯组惯性坐标系,利用加速度计获得稳定的水平坐标系;根据捷联惯组坐标系与初始时刻捷联惯组惯性坐标系的转换,将加速度计信息投影到初始时刻捷联惯组惯性坐标系,采用空间圆拟合法求出Ω的空间指向;将平行于Ω的矢量向水平面投影得到地理真北.仿真结果表明:载体晃动环境下的寻北精度达到了0.23°(1σ).

The ship rolling prevents a gyroscope from reliably measuring the angular velocity of the earth＇s rotation（Ω）.Consequently,the strapdown compass system based on fiber optic gyroscopes（FOG） cannot compute the heading of the carrier based on the outputs of gyroscopes and the accelerometers.To address this issue,a new north finding algorithm was proposed.By taking the inertial frame as the reference coordinate frame,this algorithm established the transitional inertial frame and the initial-time strapdown compass body inertial frame.The direction of vector Ω was then calculated according to the projection of the accelerometer sensitive to grivity in the initial-time body inertial frame.And this in turn recovers the true north of geographic direction.The proposed north finding algorithm consists of three steps.It established the initial-time body inertial frame.Then it obtained a stable level frame via the initial-time body frame and the outputs of gyroscope and accelerometer.By projecting the output of accelerometer from the strapdown compass body frame to the initial-time body inertial frame,the direction of vector Ω was calculated by the space circle fitting method.Then the true north was recovered by projecting the vector parallel with Ω from the initial-time body inertial frame to the stable level frame.The simulation result shows that the error of azimuth can be reduced to as low as 0.23°（1σ）.