Research On Digital Design Of Strap-down Flexible Gyroscope North Seeker And Decoupling

As inertia navigation unit is mobile, secret, free of electromagnetism interference and topographic condition,it occupies a important place in military navigation meters. Strap-down flexible gyroscope north seeker provides direction and position, navigation data for the military vehicle.Because control signals of north seeker are numerous and complex in time sequence, we use embedded controller, which is composed of DSP and FPGA, as the calculation and control unit for the north seeker. F2812 DSP chip made by TI Company, has short instruction cycle, great On-chip Flash ROM, multiple special function modules and it is responsible for the calculation and control functions. XCS-20XL FPGA chip made by XILINX Company, is responsible for the frequency division and some control functions.Digital rebalance loop is the control and measurement loop of the gyroscope. Gyro signals, which have been preprocessed, are sent to a special 16-bit A/D converter, and then DSP reads and deals with the converted data to calculate the corresponding moment data. Under Strap-down status, the moment coils of gyro should pass high current to meet the rebalance demand. We design H bridge moment circuit composed of MOS tubes, and compile the moment control program in FPGA. Base on these preparations, we carry out moment circuit linearity experiment and gyroscope room temperature drift experiment.Four positions north seeking algorithm has the advantages of eliminating gyro drift and obtaining latitude information. DSP control program is the core part of north seeker design, and the control and servo function are implemented in the interrupt service routine. The experiment of north seeker single position repeatability and full circular north seeking achieve satisfying results.Because of flexible gyro's inherent structure characteristic, the input and output signals of the X-axis and Y-axis are coupling. In order to improve north seeking precision and obtain more accurate navigation data, we should use decoupling control on flexible gyro. Diagonal matrix decoupling method is used both on rotor deflection coupling and output current coupling. Due to the lead time of military project, we only make formula derivation on decoupling, applying it to the design of Strap-down north seeker is the major step for the further research.