| SINS/GPS integrated navigation system realizes benefits including low cost,high accuracy and high real time by combining the advantages of SINS and GPS.Thus it has been widely used in various ground vehicles,ships and aircrafts.The attitude precision of SINS/GPS is closely related to the maneuvering of carrier,yaw will diverge slowly under static condition,especially for low-cost applications.Therefore,the magnetometer usually needs to be adopted as the attitude measurement.However,the magnetometer requires frequent calibration.And it is susceptible to interference,which causes navigation errors.Based on the above mentioned considerations,the Dual-Antenna GPS/SINS integrated navigation system is designed and implemented by applying the Dual-Antenna GPS as the attitude determination system in this article.Dual-Antenna GPS attitude determination technology is based on the principle of carrier phase relative positioning.The double difference observation equation is built by handling the carrier phase with double difference method,which eliminates most errors.High-precision coordinate of baseline vector can be obtained to acquire the attitude by solving this equation.Integer Ambiguity resolution algorithm is the key to resolve attitude by GPS.On the basis of the fixed-length baseline and the requirement of quick calculation of the Integer Ambiguity,an Integer Ambiguity resolution algorithm according to the QR-decomposition is proposed,which is applicable when the baseline is short and can greatly reduce the search space of the Integer Ambiguity.Aiming at the application of low-cost and multi-sensors,an integrated navigation algorithm which combines the advantages of centralized filters and federal filters is proposed in this article.The navigation parameters are directly chosen as the state variables and the state equation is obtained through linearizing the attitude,velocity and position update equations to avoid modeling and computing the inertial navigation system errors.In order to make full use of measurement data of different update frequency,time update and measurement update are executed at different frequencies,and the IMU data update frequency is considered as the foundation of the one-step prediction of state and its covariance;in addition,measurement update is conducted once the corresponding measurement arrives.This method also benefits the extension of measurement,and the computational complexity is further reduced by the application of sequential fusion.In this article,the correctness and effectiveness of the proposed algorithm are proved by completing the overall system design and verifying the static and dynamic performance of Dual-Antenna GPS attitude determination module as well as the performance of the integrated navigation system through designed experiments. |
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