What Does Gyro Navigation System Mean?
The gyro navigation system is a guidance system used to steer a microtunnel through the sub-surface.
The gyro system uses instrumentation installed at the face of the microtunnel boring machine (MTBM) to report the pitch and directional information to the operator. The gyroscope used in the gyro navigation system is basically a device that uses the Earth's gravity to determine orientation.
It consists of a freely rotating disc mounted on a spinning axis in the center of a larger and more stable wheel. As the spinning axis turns, the freely rotating disc remains stationary to indicate central gravitational pull.
Trenchlesspedia Explains Gyro Navigation System
The gyro navigation system is best suited for drives with internal diameter (ID) 800 to 1200 mm. The system uses self-leveling, north-seeking gyrocompass to determine the horizontal position and azimuth of the MTBM.
The north-seeking gyrocompass is a directional sensor that detects absolute direction from the North pole and has shown excellent results in curved microtunneling projects.
The calculations of the gyro navigation system are based on the assumption that the MTBM will move exactly along the direction defined by its axis.
The TBM drift will influence the calculation of the system and therefore the calibration of the system must be checked every 20 to 40 meters to check the TBM drift. This helps reduce the influence of the TBM drift to a minimum by pre-setting this value for further calculations.