Non-Contact, Drone-Based Technology for Movement Assessment
Based on its R&D experience, Skipper NDT decided in 2019 to address pipeline geolocation and strain assessment using UAS. This effort has provided a 2.2-kg and a 160-cm wide embedded system that can be easily mounted on any UAS (Figure 1). The main components of the system are:
- Four three-component fluxgate magnetometers
- Real-time Global Navigation Satellite System GNSS receiver with a centimetric-level accuracy
- Tactical grade inertial measurement unit (IMU)
- Telemetric sensors measuring the distance between the magnetometers and the ground (or canopy)
- Proprietary electronic card for data acquisition, digitalization, and synchronization.
The system relies on two primary sensors (magnetometers and GNSS) for the acquisition of magnetic data. Of these, the fluxgate magnetometers are particularly crucial, as they can measure the three components of the magnetic field at a sample frequency of 1000 Hz with a mass of 112 g per sensor. In comparison to scalar magnetometers, fluxgate magnetometers possess sensors that are overall lighter and more resilient, with a sampling frequency that is ten to a hundred times higher, making them more suited to the constraints of UAS. One notable advantage of fluxgate sensors is that they can capture the 3-D components of the magnetic field, making it possible to compensate for the magnetic effect of the embedded equipment and UAS. As a result, the system can be adapted to different vectors without the need for custom characterization. However, it is important to note that these fluxgate magnetometers are not absolute instruments and may contain errors related to offsets, sensitivity, and angle (non-orthogonality), which is compensated for through a proprietary calibration protocol.
