Research On Miniature High Voltage Power Supply And Dither Stripper Technology For Compact Ring Laser Gyros

Ring Laser Gyros applied in many tactical arms should have the characteristics of small size, low cost,ruggedness, fast start-up and instant reaction time. In order to fulfil these requirements,the miniature high voltage power supply and short delay signal processing circuit for three-axis ring laser gyro are studied in this dissertation. The main work is as follows:1. The miniature high voltage power supply of three-axis ring laser gyro (RLG) has been developed. The dimensions of the power supply are 4.3cm×8.0cm×1.2cm, which are less than a half of that of the single-axis RLG's high voltage power supply at present. The key techniques to minimize the volume of the high voltage power supply have been analyzed, such as selecting the topology structure of single-chip switching power supply, increasing the switching frequency of the power supply, adopting high integrated power supply chip, providing the ignition and maintenance high voltage to the gyro with a single transformer and choosing the proper current control mode and the discharge status parameter.2. High reliability discharge of the three-axis ring laser gyro has been achieved. The sequence between current stabilitating and discharge status monitoring has been controlled by adding a SPDT (single pole, double throw) switch to each current stabilitating branch of the high voltage power supply. And the discharge status monitoring has been achieved according to the voltages of the sampling resistances. Tests show that the ignition ratios of the three–axis ring laser gyro(RLG) at temperatures of -40℃, 25℃and 60℃all are up to 100% within 3.5s. And when the temperature changes from -40℃to 60℃, the current stability of each arm in the three-axis RLG is better than 1.2×10^-3 and the current difference stability of each gyro is better than 1.5×10^-4.3. By analyzing the characteristics of the gyro readout and dither feedback signal, the dither signal stripper theory based on correlation cancelling is explained in detail. Several dither stripper algorithms including Least-Square ( LS ) estimate, Least-Mean-Square(LMS)adaptive filter and Recursive Least-Square(RLS)adaptive filter have been studied separately. Analysis results show that the harmonic components and noises in dither feedback signal seriously affect the performance of the dither stripper algorithms. To improve the performance of the dither stripper algorithms, the dither feedback signal has been filtered by a band-pass filter before feeding into the dither stripper algorithms.3. Dither stripper algorithms such as the LS estimate, the LMS and the RLS have been developed in MATLAB for the purpose of stripping the dither component from the three-axis RLG readouts. Results show that the RLS and the LS estimate algorithms are good choices when effectiveness of the dither signal cancelling is considered. The standard deviation of the residual count is 0.5226″after RLS or LS estimate dither stripper, and 0.6437″after LMS dither stripper. But the LMS algorithm has the characteristics of easy implementation and high computation efficiency. The main error sources of the dither stripper algorithms have been proposed. And the quantization error of the RLG is significant for dither stripper algorithms. It has been presented that the quantization error after dither stripper can be removed by a low pass filter with a lower order.5. The hardware design of dither stripper has been successfully developed by making use of a 32-bit floating point Digital Signal Processor(DSP),a Complex Programmable Logic Device(CPLD)and an Analog-to-Digital Converter(ADC). And the software coding of the LMS plus low-order low pass FIR filter, the Cascaded Integrator Comb (CIC) low pass filter and the high-order low pass FIR filter have been implemented. The performance of the system has been tested in a three-axis RLG. Results show that the bias stability and the repeatability of the three-axis RLG obtained by the LMS plus 35-order low pass FIR filter are similar with that of the 79-order low pass FIR filter, however, the delay time can be reduced from 4.875ms to 2.125ms.The 3-order CIC low pass filter with the delay values of 60, 65 and 70 in the comb section can achieve the best performance regarding the bias stability and the repeatability, while it suffers from the longest delay of 12ms.6. The dither stripper performance of the 50-type Mechanical Dithered Ring Laser Gyro (MDRLG) has been tested on a rate table with a process including constant speed and acceleration. The test results show that the MDRLG can implement real-time angular rate measure by using of the LMS dither stripper algorithm. And the standard deviation of the angular rate in 1ms output is better than 0.2°/s. Frequency spectrums of the gyro readout and the dither feedback signal of the 50-type MDRLG before and behind vibration have been analyzed. And gyro count in 1s demodulated by means of LMS plus 15-order low pass FIR filter, CIC low pass filter and 45-order low pass FIR filter have been tested. Results show that there exist high frequency components in dither feedback signal. But it does not affect the dither stripper performance because the feedback signal has been filtered by a band-pass filter before feeding into the LMS algorithm. And there are low frequency vibration components in the gyro readout. That makes the standard deviation of the gyro count increased.The gyro average counts demodulated by the aforementioned three methods are almost identical.