Statistical sensor fusion of ultra wide band ranging and real time kinematic satellite navigation

Real Time Kinematic (RTK) Global Positioning System (GPS) uses carrier phase measurement from GPS signal and it has a high accuracy but has integer ambiguity resolution problem which causes cycle slips and requires good satellite visibility as well. RTK was originally developed for applications such as surveying; in our case the target application is the tracking and the control of a robot hexacopter. The main issue in RTK is the determination of the number of cycles, called integer ambiguity, between the receiver and each satellite. Once the ambiguity is solved, it remains constant as long as the receiver maintains a phase lock on the satellite signals. However, the hexacopter maneuvers or the satellite visibility obstructions can cause the loss of phase lock, and the integer ambiguity needs to be solved again which result in degradation of RTK GPS positioning. This paper presents fusion of Ultra-Wide Band (UWB) and RTK GPS positions through loosely coupled approach in Kalman filter to overcome this issue. Measurement results show that the fusion of UWB and RTK GPS positioning solutions have better performance compared to stand-alone RTK GPS solution.