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The rigorous requirements of modern spacecraft missions necessitate a precise attitude determination strategy. This paper mainly researches that, based on three space-borne attitude sensors: 3-axis rate gyros, 3-antenna GPS receiver and starsensor. To obtain global attitude estimation after an information fusion process, a feedback-involved Federated Kalman Filter (FKF), consisting of two subsystem Kalman filters (Gyros/GPS and Gyros/Star-sensor), is established. In these filters, the state equation is implemented according to the spacecraft’s kinematic attitude model, while the residual error models of GPS and star-sensor observed attitude are utilized, to establish two observation equations, respectively. Taking the sensors’ different update rates into account, these two subsystem filters are conducted under a variable step size state prediction method. To improve the fault tolerant capacity of the attitude determination system, this paper designs malfunction warning factors, based on the principle of χ² residual verification. Mathematical simulation indicates that the information fusion strategy overwhelms the disadvantages of each sensor, acquiring global attitude estimation with precision at a 2-arcsecs level. Although a subsystem encounters malfunction, FKF still reaches precise and stable accuracy. In this process, malfunction warning factors advice malfunctions correctly and effectively.

Pedestrian navigation system (PNS) is also known as the walker navigation system, which is mainly used to track and posit real-time position of walker, to provide walk speed and position of walker, and also be applied to military, science, sport, rescue, the blind navigation, electronic product, etc. GPS signal is unreliable and difficult to provide accurate location information in most environments such as indoor, urban streets and canyons. At this point, the autonomous navigation system based on the proposed algorithm is a good solution. This article mainly analyzes the MEMS inertial device in the actual engineering practice, the application of the low precision of MEMS inertial device used in personal navigation correction algorithm, and combines the MEMS inertial sensors and GPS receiver, satisfies the requirement of pedestrian positioning. Using the complementary filter to fuse sensor data, we can obtain information of high precision orientation.

In order to achieve the requirements of high precision and update rate satellite attitude determination, attitude determination solution based on star-sensor and gyro filtering algorithm is proposed. Quaternion model is established for satellite attitude determination, and Extended Kalman Filter is used to complete the fusion of sensor information as well as the correction of attitude error and gyro drift error. For the gyro's update rate is much higher than the star sensor’s, two multi-step-length attitude determination methods which are direct integration method and P-matrix (estimate error covariance matrix) one-step prediction method are designed, during the star-sensor’s output interval, the first method directly uses the gyro’s output to estimate the attitude quaternion, the second method predicts P-matrix (estimate error covariance matrix) additionally based on the first method. Combined with mathematical simulation and analysis, it is concluded that both multi-step-length satellite attitude determination methods can provide higher precision and update rate satellite attitude than fixed-step-length method. Considering the small difference between the estimation precisions of two multi-step-length methods, direct integration method is more applicable than P-matrix one-step prediction methods.

*† ‡ § SINS is usually in the existing GPS/SINS integrated navigation hardware-in-the-loop simulation system. However, there isn’t any literature about GPS receiver concerned with the hardware-in-the-loop simulation system. GPS still rests on mathematic simulation. Generally, GPS position result is from computer simulation, or the error model of GPS is obtained by some means and added to the normal data during the simulation. Because GPS receiver is not in the loop, the simulation condition is different from reality. The simulation fidelity is not high. The GSS6560 Multi-channel GPS/SBAS Simulator produced by Spirent Communications can be controlled remotely to receive motion data of the vehicle. It can simulate the motion of the vehicle and the signals of GPS satellites. This paper takes advantage of this characteristic of GSS6560 GPS simulator and adds GPS receiver to GPS/SINS integrated navigation hardware-in-the-loop simulation system. Experiment has been done and result shows that the simulation system works quite well and meets the requirement.