Time-varying gyrocompass alignment for fiber-optic-gyro inertial navigation system with large misalignment angle

Abstract. Conventionalstrapdowngyrocompassalignmentmethodsarebasedontheassumptionthatthefiber-optic-gyro inertial navigation system has a small azimuth misalignment angle. A large azimuth misalignmentangle would lead to an extension of the alignment duration. A time-varying gyrocompass alignment methodto solve this problem is provided. An appropriate parameter setting is given for the gyrocompass alignmentwith a large misalignment angle. Also, a proper protocol for a parametric switch is derived. Simulation andtrail results show that the proposed method has better alignment performance than conventional ones, asthe system has large misalignment angles. © 2014 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.53.9.095103] Keywords: fiber-optic-gyro; inertial navigation system; gyrocompass; alignment.Paper 140457 receivedMar. 21, 2014; revised manuscript received Aug. 14, 2014; accepted for publication Aug. 15, 2014; publishedonline Sep. 11, 2014. 1 IntroductionThe fiber-optic-gyro (FOG) inertial navigation system (INS)features the benefits of fiber-optic-gyro technology andtherefore shares the advantage of requiring no maintenanceand recalibration. It belongs to strapdown INS and has sub-stituted for platform INS. The initial alignment is one of thekey technologies of FOG INS, as alignment accuracy andspeed directly affect the performance of FOG INS. Inmany applications, we need to accomplish the initial align-ment with high accuracy and rapid speed.TheclassicalgyrocompassalignmentmethodproposedinRef. 1 based on thegyrocompass effect and feedback controltheories was originally used in the platform INS, and thenwas applied in the FOG INS