Real-Time Navigation System for Ultra-Tight Integration of GNSS and Multi-Sensors

Global Navigation Satellite Systems (GNSS) plays an important role in today's positioning, navigation and guidance systems and has been widely used in various applications. GNSS receivers, according to their application areas, can be classified as high precision receivers or high sensitivity receivers. High precision receivers can provide centimeter-level positioning accuracy using carrier phase measurements but with lower acquisition and tracking sensitivity. In comparison to high precision receivers, high sensitivity receivers offer improved sensitivity with certain compromises of positioning accuracy. It is noted that even high sensitivity GNSS receivers would suffer degraded performance or completely fail to operate in urban canyon or indoor environments where GNSS signals are severely attenuated, jammed, reflected, or blocked. Given the limitations of GNSS-only navigation systems, inertial sensors, barometers, magnetometers, and various sensors can be integrated with GNSS receivers to provide a continuous, always-available, and reliable navigation solution. This paper presents a real-time ultra-tightly coupled GNSS and multi-sensor integrated navigation system. The proposed system uses ultra-tight integration with a low cost micro-electro-mechanical-systems (MEMS) inertial measurement unit (IMU), and optional barometer, magnetometer and odometer. The proposed navigation system is able to provide reliable navigation solution even in challenging GNSS environments. The prototype system is implemented on a FPGA/ARM based hardware platform, which can be used either as a: (i) tethered navigator for machine or vehicles; or (ii) portable navigator. A novel aspect of the presented work is the utilization of ultra-tight integration for GNSS and multi-sensor integration instead of loose or tight ones. Furthermore, unlike previous works of the ultra-tight system using post-processing or simulation, real-time results from the proposed system are presented and analyzed. The performance of the ultra-tight integrated system has been verified on real-life road tests. The results have been examined to verify the suitability and satisfactory performance of the solution, even in deep urban canyon environments.