Helmert variance component estimation Helmert variance component estimations 3 IMU pre‐integration 3 Inertial measurement unit pre‐integration 3 Inertial measurements units 3 Integration 3 Kalman filters 3 Mobile robots 3 Multi-state 3 Odometry 3 Positioning accuracy 3 Pre-integration 3 State constraints 3 Visual–inertial odometry 3 Wheel odometry 3 Wheels 3 mobile robot 3 visual–inertial odometry 3 wheel odometry 3