Adaptive Compensation Hxe2x88x9e Filter with Convergence Criterion for SINSxe2x80x99 Transfer Alignment Transfer alignment under the unknown external environment is a challenging problem in strapdown inertial navigation system (SINS). To suppress the filtering divergence when conducting transfer alignment, an adaptive compensation Hxe2x88x9e filter is proposed. This paper analyzes the cause of filtering divergence carefully and accordingly makes the corresponding adjustment and optimization. With the change of the unknown external environment, the robustness factor of the proposed filtering method can be dynamically adjusted. To solve the problem that the transfer alignment time is mainly determined according to experiences, the convergence criterion of the proposed filtering method is studied. The convergence criterion is based on the principles of mathematical statistics, and can automatically determine the convergence time of the filter. The aerial transfer alignment experiment illustrates that by using the convergence criterion, the alignment time can be effectively shortened and the response speed can be effectively improved.

A New InFlight Alignment Method with an Application to the LowCost SINSGPS Integrated Navigation System The optimizationbased alignment (OBA) methods, which are implemented by the optimal attitude estimation using vector observationsxe2x80x94also called doublevectorsxe2x80x94have proven to be effective at solving the inflight alignment (IFA) problem. However, the traditional OBA methods are not applicable for the lowcost strapdown inertial navigation system (SINS) since the error of doublevectors will be accumulated over time due to the substantial drift of microelectronic mechanical system (MEMS) gyroscope. Moreover, the existing optimal estimation method is subject to a large computation burden, which results in a low alignment speed. To address these issues, in this article we propose a new fast IFA method based on modified doublevectors construction and the gradient descent method. To be specific, the modified construction method is implemented by reducing the integration interval and identifying the gyroscope bias during the construction procedure, which improves the accuracy of doublevectors and IFA; the gradient descent scheme is adopted to estimate the optimal attitude of alignment without complex matrix operation, which results in the improvement of alignment speed. The effect of different sizes of minibatch on the performance of the gradient descent method is also discussed. Extensive simulations and vehicle experiments demonstrate that the proposed method has better accuracy and faster alignment speed than the related traditional methods for the lowcost SINSglobal positioning system (GPS) integrated navigation system