Fig. 1. System framework

Fig. 2. Factor graph for tightly coupled integration of IMU and LiDAR

Fig. 3. Time-space threshold key frame selection strategy

Fig. 4. Local map construction method

Fig. 5. Simulation trajectories comparison of three algorithms. (a) Global trajectory; (b) starting trajectory; (c) corner trajectory; (d) straight trajectory

Fig. 6. z-axis trajectory of three algorithms

Fig. 7. Robot platform

Fig. 8. Trajectories comparison of two algorithms. (a) Global trajectory; (b) starting trajectory; (c) corner trajectory; (d) straight trajectory

Fig. 9. z-axis error of two algorithms without corner smoothing

Fig. 10. z-axis error of two algorithms with corner smoothing