Research On GPS-based Attitude Determination System

Global Position System(GPS) is not only well known for determination of vehicle position, velocity in real-time and all-weather conditions, but also processing the differential carrier-wave phase received by multi-antennas installed on the same vehicle and layout in a proper array to resolve the attitude of vehicle in real-time. Multi-antenna attitude determination of GPS is without accumulated error, aiming, and is all-weather, low-power navigation system which is beyond using precise mechanical technology, therefore, it is gradually replacing the traditional measurement way by using GPS more and more in space survey, aviation, shipping and other fields.In this paper, GPS attitude determination technology was researched in the aspect of attitude determination theory, baseline resolution, ambiguity resolve algorithm, and a pint-sized, low-power, strongly scalable attitude determination system was designed which is distinguished with classical ones that has accumulated error, which was merged with the characteristic of ARM embedded system. Main work which was included in the paper is made up of the following parts:1, An ARM based embedded attitude determination system scheme was put forward based on the research of domestic development status and abroad with great efforts, and deeply analysis of the features of attitude determination system based on GPS.2, Attitude determination theory based on GPS was researched. Under the premise of transformation of several common coordinate system was cleared, baseline resolve algorithm and Ambiguity Resolution On The Fly(AROF or OTF) algorithm was analyzed. Furthermore, optimized Ambiguity Function Method(AFM) based on assuming integer double-differential was researched, the attitude resolution in the algorithm by using assuming ambiguity was done concisely by direct method rather than ever before, and it was greatly reduced of the ambiguity's searching range because of geometric constraint being used of in the algorithm. Thus, the ambiguity could be resolved rapidly and the real-time resolution of baseline by using the direct analytical method could be implemented based on that. The algorithm greatly reduced the time of computing and improved the reliability compared with the traditional AFM.3, An embedded attitude determination platform based on ARM was designed, which was composed with the CPU AT91SAM9261 as core, SDRAM, FLASH, RS422 converter chips and so on. The schematic diagram and PCB layout was designed, signal integrity simulation and hardware debugging was accomplished, bootloader was improved and transplanted, attitude determination software was implemented.4, The experiment was carried out by using Crescent HC12A and other two types of GPS OEM boards combined with ARM embedded system to compose the attitude determination system. The results indicate that: The precision of yaw, pitch and roll angle achieves 0.6°(1σ) without accumulated error under the baseline was 1 meter. The detailed analysis of the main performance index in the experiment was taken, and the research direction of improving system performance further was discussed.It is totally contained in the paper that of 45 figures, 1 table and 30 references.