En navigation inertielle, une antenne fait généralement référence à l'appareil qui reçoit des signaux de systèmes de positionnement externes, le plus souvent des systèmes mondiaux de navigation par satellite (GNSS) , tels que GPS, GLONASS, Galileo ou BeiDou. L'antenne est cruciale pour fournir des informations de position absolue (latitude, longitude et altitude) et faciliter l' initialisation et la correction du système de navigation inertielle (INS).
Rôle de l'antenne dans la navigation inertielle :
Réception des signaux GNSS:
- The antenna receives signals from GNSS satellites that broadcast their position and time data. This allows the INS to determine the absolute position and velocity of the system, which can be used to correct or calibrate the inertial sensors (accelerometers and gyroscopes) over time.
Positioning and Navigation:
- The GNSS data provided by the antenna helps to establish the position of the device in space. This information is particularly important for determining initial position and for performing corrections to the inertial navigation system’s estimates of position and velocity over time, especially in the absence of other reference systems.
Fusion with Inertial Sensors:
- In a typical sensor fusion approach, data from the GNSS antenna and the inertial sensors (IMU) are combined using algorithms like Kalman filtering to provide accurate, continuous navigation information. The inertial sensors provide short-term accuracy, while the GNSS data corrects long-term drift.
Role in Initialization:
- During system startup or when the INS cannot obtain sufficient inertial measurements, the GNSS antenna provides vital data for initial alignment and calibration of the system, especially for the initial position and heading.
Aiding in Accuracy:
- In the case of dual-antenna systems or multiple antennas, the relative position between the antennas can be used to compute heading, roll, and pitch. This is common in applications like marine, aerospace, and land vehicle navigation, where accurate heading and attitude are required.
For example:
- Single-antenna systems rely on GNSS data alone to update the position, while
- Dual-antenna systems use two antennas placed at a fixed distance apart to calculate heading, which is then used to correct the INS.
Impact of Environmental Factors:
- The performance of the antenna can be affected by environmental factors like signal blockage, multipath interference (reflected signals), or atmospheric conditions, which may impact the quality and reliability of the GNSS data. This is particularly problematic in urban canyons or dense forests, where signals may be blocked or reflected.
Types of Antennas in Inertial Navigation:
- Patch Antennas:
- These are small, flat antennas often used in GNSS receivers for applications requiring low-profile designs. They can be used in both single- and dual-antenna configurations.
- Helical Antennas:
- Used for applications where the antenna needs to provide better signal reception in a specific direction (e.g., aircraft, marine vessels).
- Dual-Antenna Systems:
- In applications where heading and attitude need to be determined, dual-antenna systems are used. These systems measure the relative position between two antennas to calculate the heading (direction of travel), which can then be fused with inertial measurements.
- Microstrip and L1/L2 Antennas:
- These antennas can operate on specific GNSS bands (e.g., L1 for GPS) and may offer high accuracy and resistance to signal interference.
Conclusion:
In inertial navigation, the antenna is a vital component for providing absolute position data through GNSS signals, which helps to correct the accumulated errors (drift) in the inertial measurement unit (IMU). By combining the data from the antenna with the measurements from the IMU, the system can achieve higher accuracy and reliability in navigation, especially over longer periods and in environments where inertial sensors alone would experience drift.
