Phase Modulation-Based SINS Damping Method for Autonomous Vehicles

Compared with many other types of navigation systems, the greatest advantage of strapdown inertial navigation system (SINS) is entirely self-contained. It can work autonomously without any external aids. Therefore, improving the navigation accuracy of SINS in pure inertial state is of great significance especially for autonomous vehicles. Traditional damping methods of inertial navigation system (INS) for Schuler error suppressing were mainly based on a second-order or third-order damping network. However the traditional methods work fine only when the external speed information is available. If there is an error in the external speed or lack of external information, traditional methods will produce some errors in navigation outputs. So some problems still exist to be tackled down. For the purpose of solving the problems of traditional methods, a completely autonomous damping method called phase modulation-based SINS damping method (PMD for short) is proposed in this paper. Two calculation loops are established for damping of SINS. Using virtual extended inertial data, phase difference of the two loops is constructed based on the analysis of the error characteristics of SINS. By averaging the outputs of the two loops, the Schuler oscillation errors in attitude, velocity, and position are mostly suppressed. Both of the two loops keep in pure inertial state, and no external aid is required in PMD. Simulation and field experiments demonstrate the validity of the proposed method.