The Development Of Miniaturization Navigation CPU Board Based On The Technology Of DSP And CPLD Applied In Laser Gyro Strapdown Inertial Navigation Systems

At present, Strapdown Inertial Navigation Systems (SDINS) based on Ring Laser Gyros (RLG) are used more and more widely. In certain tactical applications, the SDINS must be small and compact enough. So not only the Inertial Measurement Unit (IMU) but also the signal processor circuit must be miniature. Now, the size of three-axis RLG can be less than Φ80 × 100mm, however the old navigation CPU board is too large. In order to adapt to miniature applications, a miniaturization navigation CPU board based on the technology of DSP and CPLD is developed in this paper.The main work in this paper including:(1) Realizing the miniaturization signal processing circuit. The size of the miniaturizationCPU board designed and manufactured in this paper is 78 × 85mm~2.(2) Depend on the theory of RLG's signal processor, the count circuit, the phase-demodulation circuit, the frequency multiplication circuit and the control circuit have been designed with CPLD.(3) The clock matching has been designed between CPLD and DSP. In CPLD, separate clocks are provided for both the counter and the storage register. The counter clock is provided by crystal oscillator, and the storage clock is controlled by DSP unit. The DSP sends out a storage pulse before reading the data of counter. Then, the storage clock of CPLD will never conflict with the reading clock of DSP.(4) After compiling and debugging the DSP, it is proved that the A/D converter function, the serial communication function and the I/O function can work properly.(5) A FIR(finite impulse response) low pass digital filter is designed based on DSP. It accomplishes the functions of sampling the signal of Mechanically Dithered Ring Laser Gyroscopes (MDRLG) and eliminating the dither and the high frequency noise.In the end, the experiments and test results show that the miniaturization CPU board can work in gear and that the count function of the signal of accelerometers ,the functions of phase-demodulation, frequency multiplication and the count of the signal of MDRLG have been accomplished .At the same time, it can be prepared for the future development, because thisdesign only occupies a few resources of DSP.