Research On The Receiver Autonomous Integrity Monitoring Of Multi-Constellation And Multi-Fault

With the continuous improvement of America’s GPS and Russia’s GLONASS, the all-around construction of EU’s GALILEO system and China’s BeiDou Navigation Satellite System (BDS/COMPASS), the Global Navigation Satellite System (GNSS) develops rapidly. The increasing emphasis is attached to multi-constellation navigation technology in the world. And the technology will become the mainstream in the future. Under multi-constellation joint navigation, the occurrence of satellite fault and multi-satellite fault will increase, and it affects aviation safety. So, integrity, an issue closely linked to safety, is users’major concern. Receiver autonomous integrity monitoring (RAIM) is one of the common integrity monitoring technologies. It can detect and identify satellite faults by using the redundant observed values of the receiver. Without assistance of external devices and with the advantages of low cost, fast detection speed and easy implementation, it is applied extensively. So, it is of relatively great scientific and practical significance to study multi-constellation and multi-fault RAIM.At present, multi-constellation navigation technology is a hot research spot at home and abroad. However, the systematical studies on multi-constellation and multi-fault RAIM are rarely few. So, it is the subject of the paper. The main content includes:1. The principle of RAIM algorithm and factors influencing its performance are analyzed. On that basis, the general process of multi-constellation RAIM is created. Traditional RAIM is applied to the multi-constellation navigation system. The performances between multi-constellation RAIM and single-constellation RAIM are compared through simulation from 4 aspects:number of visible satellites, GDOP, availability, fault detection and identification.2. The deficiency of traditional RAIM algorithm in identifying double-fault is analyzed, and double-satellite RAIM algorithm which is based on fault characteristic-plane is studied. Then, double-satellite RAIM algorithm is improved by QR decomposition. Finally, the performance of the algorithm is verified through simulation.3. Since traditional RAIM cannot detect tiny slow-varying deviation, two multi-epoch accumulation methods (TVP-TAIM algorithm and incoherent accumulation method) dealing with tiny slow-varying deviations under GPS single constellation are studied in depth. The multi-epoch accumulation method is applied to multi-constellation cases and further applied to the cases of medium deviation and gross deviation. Simulation verification shows multi-constellation multi-epoch accumulation method can greatly enhance the detection rate of pseudo range derivation whether in tiny deviation, medium deviation or gross deviation. The greater the number of accumulated epochs is and the smaller the detectable pseudo range derivation is, the higher the detection rate will be.4. On the basis of multi-constellation multi-epoch accumulation RAIM algorithm, a new method to detect and identify multi-constellation double-fault——multi-epoch accumulation double-fault method is proposed. It can detect double-fault at tiny, medium and gross deviations. Simulation comparison indicates that the greater the number of accumulated epochs is, the higher the rate of double-satellite fault identification will be. Meanwhile, the sensitivity and robustness of fault identification rate will also be higher.