In the last decade, inertial sensor technology has become growingly appealing for tracking applications, thanks to the decrease of production cost and improvement in performance. In navigation applications where position information is required, an Inertial Measurement Unit (IMU) is typically combined with GNSS (Global Navigation Satellite System) information. So far, GNSS/INS solutions (where INS stands for Inertial Navigation System) have typically been designed as devices having an integrated GNSS receiver (e.g., XSENS MTi-G-710) or as devices accepting data from a GNSS receiver external to the device by means of electro-mechanical interfaces. However, both approaches typically limit the range of employable GNSS receivers and/or antennas and, consequently, might negatively affect integration capabilities, final application design, cost, and performance. Recently, Xsens designed and released a miniature motion-tracking module with an SMD (Surface Mounting Device) form factor of 12.1×12.1 mm and with support for multiple external GNSS receivers, offering the smallest SMD-based GNSS/INS module running advanced embedded sensor fusion algorithms. The proposed design uses permanent electrical connections to both solder the device to the application platform and gather the external GNSS signals. This solution enables a seamless and robust integration of the device by taking advantage of the existing GNSS infrastructure, eliminates the need for additional dedicated electro-mechanical interfaces, and preserves the signal communication integrity between the device and the host system. The hardware consists of a 3-axis gyroscope, a 3-axis accelerometer, a 3-axis magnetometer, a high-accuracy crystal, and a low-power Micro Controller Unit (MCU). In addition to external GNSS, the device is also able to accept other aiding sensor inputs (e.g., barometers) to further improve the performance of the final solution. The device power consumption lower than 100 mW and its limited weight make it ideal for low-level integration with emerging application platforms such as drones, UAV's (Unmanned Aerial Vehicle), UGV's (Unmanned Ground Vehicle), and in fields like smart farming, unmanned control, Internet of (Moving) Things, and robotics. The performance are evaluated in a typical application scenario of relevance. Estimated 3D position, velocity, and orientation have been compared against those derived using a GPS/L1/L2/GLONASS multi-GNSS multi-frequency receiver used in combination with a tactical grade fiber optic gyros (FOG) during a car-driving scenario. The results showed RMS errors lower than 1 deg and 2 deg respectively for roll/pitch and heading angles, lower than 2 m for position, and lower than 0.2 m/s for velocity.
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