Research On Techniques Of Transfer Alignment Using Micro Strapdown Inertial Navigation System

Transfer alignment is the key technology of micro strapdown inertial navigation system (MSINS) implemented in precision guided weapons. According to the key problems occurred in in-flight transfer alignment of MSINS, detailed theoretical analysis, simulation and tests were carried out based on the world-wide research achievements in related fields.This dissertation proposed a MINS transfer alignment model, which introduced the random constant bias of gyros and accelerometers as the filtering state parameter to estimate. The velocity & attitude matching, the velocity matching and the attitude matching methods were compared, while the first method showed the optimal estimation performances. An improved adaptive Kalman filter was also proposed to mitigate the impact of observation noise variation. The novel filter stabilized the filter process, and improved the filtering quality.The Markov stochastic models of aircraft wing flexure deformation were studied based on analysis of inertial measurement data from a flight test. The wing flexure’s main frequency range (5~10 Hz) was close to the filter frequency of the transfer alignment, thus the wing flexure could not be estimated effectively by the transfer alignment filter with a wing flexure Markov model. Three methods to mitigate the estimation precision reduction caused by wing flexure were put forward, including suboptimal Kalman filter method, prepositive lowpass filter method and velocity & double-integration of angular rate matching method, all of which had been validated through Monte Carlo simulation.A PWCS (Piece-Wise Constant System) observability reverse analysis method as well as an observability-degree analysis method based on PWCS models were developed. The observability and the observability-degree of velocity & attitude matching and the velocity matching were analyzed by the novel methods. The comparison showed that velocity & attitude matching had a higher degree of observability, lower aircraft maneuver requirement and faster filter convergence. Moreover, only the attitude modification was required to converge the filter during the velocity & attitude matching alignment.With the simulation of a guided bomb trajectory, the relationship between the guided bomb total position error and the error sources was analyzed, and the applicable transfer alignment requirements for micro-machined inertial navigation systems were proposed. It was suggested the specific maneuver for transfer alignment should be replaced by ordinary maneuvers, and the alignment precision should be maintained. The new maneuver schemes could enhance the combat efficiency and the survival capability of aircrafts. The transfer alignment simulation of climbing, sliding and turning maneuvers proved the feasibility. To keep the alignment precision after transfer alignment, the whole-track transfer alignment method and the attitude matching tracking method were developed. The two novel methods were both validated through simulation.Vehicle tests were carried out to evaluate the transfer alignment methods proposed in the dissertation. Under the test vehicle maneuver condition, the transfer alignment results satisfied the alignment requirements for guided bomb with micro inertial navigation system.