Global Positioning System Reference
In-Depth Information
Fig. 11. Maximum errors for altitude and 2D position for the seven outages in second
trajectory.
the maximum positional error for the seven GPS outages equal to 7.64 meters while the case
without updates has 68.29 meters of error.
When comparing KF with RISS and velocity updates to KF with full IMU and velocity updates
the advantage of RISS can be seen especially in the altitude component. The former has an
average of the maximum positional error for the seven GPS outages equal to 7.64 meters while
the latter shows an error of 11.44 meters. The former has an average of the maximum altitude
error for the seven GPS outages equal to 3.68 meters while the latter shows an error of 19.53
meters.
These results together demonstrate that the 3-D localization solution using KF for RISS/GPS
integration and employing velocity updates using wheel encoders outperforms all the other
compared solutions. Furthermore this solution provides very good results when compared to
the MEMS-based INS/GPS integration results in the literature.
5. Conclusion and future work
This chapter presented an outdoor 3-D localization solution for mobile robots using low-cost
MEMS-based sensors, wheel encoders and GPS. A reduced inertial sensor system was used
for both decreasing the cost and improving the performance. The integration was achieved
using a loosely-coupled KF. In this work, a predictive error model for KF was developed
for estimating the errors in positions, velocities and attitude provided by RISS mechanization.
Using this error model inside the KF gives good results during GPS outages that outperformed
the full IMU results. Furthermore, when this KF is used with measurement updates using
forward velocity from encoders together with pitch and azimuth estimates (during GPS
outages) it provides better results and outperforms all the compared solutions.
The positioning solutions in this work were tested with two real trajectories with seven
simulated GPS outages whose duration was 60 seconds in the first trajectory and 150 seconds
in the second trajectory. The proposed solutions were discussed and compared with each
solution also compared against a reference solution. Considering the maximum error in
horizontal positioning in the first trajectory, the KF with RISS and velocity updates during
GPS outages achieved an average improvement of approximately 97.6% over KF with full
IMU without any updates during outages, of approximately 61.8% over KF with full IMU
Search WWH ::
Custom Search