A navigation method for IMU/odometer fusion based on horizontal attitude constraints

The current inertial measurement unit (IMU) and odometry fusion navigation algorithms often incorporate non-holonomic constraints (NHC) to obtain three-dimensional velocity in the navigation frame. However, due to the integral nature of the dead reckoning algorithm, the attitude errors of the IMU accumulate over time, causing the velocity transformation results to fail to accurately reflect the three-dimensional velocity in the navigation frame. Based on the fact that during a vehicle's horizontal and uniform motion, the vertical acceleration is consistent with gravitational acceleration, this paper proposes an IMU/odometry fusion navigation algorithm based on horizontal attitude constraints (HAC). Building on non-holonomic constraints, this algorithm determines the motion state of the vehicle through accelerometer output and zeroes out the pitch and roll angles during horizontal and uniform motion. Verified through two sets of real-world vehicle test data, this algorithm improves horizontal positioning accuracy by approximately 63% and 70%, and vertical positioning accuracy by 98% and 97%, compared with the traditional NHC IMU/odometer fusion algorithm.