The Research And Application Of The North-seeker's Transposition Control Algorithm

The north-seeker is using the gyroscope to measure the horizontal component of the earth rotation rate in order to obtain the information on the angle to the north, and at the same time measure the tilt angle of the base using accelerometer, through analyzing the two above information, the angle between the north-seeker's reference axis and the true north is gained. However, in the north-seeker there are many error sources, which directly affect the precision of the north-seeker. The transposition error producing by its mechanism is a more important source, which affects largely the results of the north-seeker.Aiming at the above, this thesis expounds in isolation the working principle of the north-seeker's indexing mechanism and the precision demand for transposition system on the basis of introducing the north-seeker and north-seeking scheme.Through the comparative analysis of the transposition control algorithm and combining the advantages of the FPGA chip of EPF10K50RI240 of Altera Company, this thesis takes solid-axes photoelectric encoder of the ZSP5.208 series as the position detecting circuit of transposition control system and achieves its precision demand.This thesis provides the general design scheme of the transposition control system, and respectively expounds its hardware circuit design and the software implementation of the FPGA control system. In designing the hardware circuit, the driving circuit of the stepper motor and the position detecting circuit of transposition system reached analysis. In the software implementation of the FPGA control system, the software selects the fuzzy-PID control algorithm to control the positioning accuracy of the transposition control system and chooses the lift frequency control algorithm to control its stationarity. Besides, this software communicates the upper computer through the serial communication circuit and achieves the normal operation of the whole system. On the basis of EDA software platform, the software uses the top-down design method and conducts synthesis, optimization, placement and routing, simulation test, and so on.Relying on the cooperation project demands of the R&D institution in Chongqing, this thesis tests and verifies the north-seeker after completing the overall design. The transposition precision testing of the north-seeker is mainly demarcated in the large biax rate turntable, and it measures the repeatability in the process of transposition and its working performance in high or low temperature test environment. Through the analysis of test data, it shows that the repeatability of the transposition system and the precision of the north-seeker in high or low temperature test environment can meet the accuracy requirement of the system.