Benefits of Multi-Constellation/Multi-Frequency GNSS in a Tightly Coupled GNSS/IMU/Odometry Integration Algorithm

Area of Science:

• Automotive Engineering
• Geomatics Engineering
• Robotics

Background:

• Localization algorithms are crucial for automotive positioning, especially with the rise of autonomous vehicles.
• Current Global Navigation Satellite System (GNSS)/inertial measurement unit (IMU) integration often relies on single-frequency, single-constellation systems (e.g., GPS L1 C/A).
• Increasing performance demands for vehicle control necessitate enhanced localization accuracy beyond traditional GNSS capabilities.

Purpose of the Study:

• To upgrade a tightly coupled GNSS/IMU integration algorithm for multi-frequency and multi-constellation satellite navigation.
• To evaluate the performance improvements gained by incorporating new GNSS signals and odometry data.
• To assess the impact of differential code biases (DCBs) calibration for multi-constellation processing.

Main Methods:

• Developed a GNSS/IMU integration algorithm processing GPS (L1 C/A, L2C, L5) and Galileo (E1, E5a, E5b) signals.
• Utilized ionosphere-free combinations (L5-L1 C/A, E5a-E1) and backup combinations for pseudo-range measurements.
• Incorporated time-differenced carrier-phase measurements for pseudo-range-rate observations and odometry data (wheel speeds, steering angle) for aiding.

Main Results:

• The multi-frequency/multi-constellation algorithm with odometry aiding achieved a 3-D root mean square (RMS) position error of 3.6 m / 2.1 m.
• This represents an improvement over the single-frequency GPS algorithm without odometry aiding, which had an RMS error of 5.2 m / 2.9 m.
• Odometry aiding proved most beneficial in poor GNSS conditions, reducing the horizontal position error's 95% quantile from 6.2 m to 4.2 m in one dataset.

Conclusions:

• Multi-frequency and multi-constellation GNSS, combined with IMU and odometry, significantly enhances automotive localization accuracy.
• The developed algorithm effectively handles multiple GNSS signals and incorporates essential sensor fusion for robust positioning.
• Odometry aiding is a critical component for maintaining high positioning accuracy, particularly in challenging GNSS environments.