Improved INS/VNS integrated navigation measurement model for lunar rover

The INS/VNS integrated navigation is an important autonomous navigation method for lunar rovers. Traditional INS/VNS integrated navigation methods which utilize the relative motion differences between the inertial and the vision as measurements, usually make an approximation between the inertial attitude errors and the misalignment angle to simplify the relative rotation measurement model. However, the approximation error can exceed the misalignment angle when the head is large, which cannot be ignored. To solve this problem, a new measurement error analysis method was presented which can avoid the approximation in traditional method, and build the corresponding improved measurement model. The known inertial attitude which contains error utilized to get more accurate error expression of relative inertial rotation quaternion, and reduce the forecast error of relative rotation difference between the inertial and the vision. Both of the Moon-based simulation and the Earth-based experiment demonstrate that the presented method is effective and can achieve higher accuracies of positions and attitudes than the traditional one, in which the position accuracy has improved 68% from 0.456% to 0.143% in the Earth-based experiment.