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

Research on the Integrated Navigation Technology of SINS with Couple Odometers for Land Vehicles Autonomous and accurate acquisition of the position and azimuth of the vehicle is critical to the combat effectiveness of landfighting vehicles. The integrated navigation system, consisting of a strapdown inertial navigation system (SINS) and odometer (OD), is commonly applied in vehicles. In the SINSOD integrated system, the odometer is installed around the vehiclexe2x80x99s wheel, while SINS is usually installed on the base of the vehicle. The distance along SINS and OD would cause a velocity difference when the vehicle maneuvers, which may lead to a significant influence on the integration positioning accuracy. Furthermore, SINS navigation errors, especially azimuth error, would diverge over time due to gyro drifts and accelerometer biases. The azimuth error would cause the divergence of deadreckoning positioning errors with the distance that the vehicle drives. To solve these problems, an integrated positioning and orientation method based on the configuration of SINS and couple odometers was proposed in this paper. The proposed method designed a high precision integrated navigation algorithm, which compensated the lever arm effect to eliminate the velocity difference between SINS and odometers. At the same time, by using the measured information of couple odometers, azimuth reference was calculated and used as an external measurement to suppress SINS azimuth errorxe2x80x99s divergence over time, thus could further improve the navigation precision of the integrated system, especially the orientation accuracy. The performance of the proposed method was verified by simulations. The results demonstrated that SINS2ODs integrated system could achieve a positioning accuracy of 0.01% D (total mileage) and orientation accuracy of xc2xb130xe2x80xb3 by using SINS with 0.01xc2xb0h FiberOptic Gyroscope (FOGs) and 50 xc2xb5g accelerometers.