基于FIR滤波和抖动剥除相结合的激光陀螺无延时测量方法

A non-delay measurement method for RLG based on the combination of FIR filtering and dither stripping

对于雷达天线伺服跟踪这种高动态应用环境,传统的有限脉冲响应(Finite impulse response,FIR)低通滤波抖动解调引入的时间延迟会导致较大的跟踪误差。为了解决时间延迟问题,文中提出一种FIR滤波与抖动剥除相结合的测量方法,FIR实现具有时延的精确解调,抖动剥除对FIR延迟时间段进行精确补偿。抖动剥除基于相关抵消原理,通过Kalman滤波对陀螺抖动剥除增益因子进行动态跟踪,并对时延前后的抖动量进行实时计算。文中对无延时测量方法进行了激光陀螺实验测试,测试结果表明:该测量方法能够对FIR时延时间段的抖动量进行精确计算,抖动剥除精度优于0.5″,实现了陀螺无延迟测量。FIR滤波和抖动剥除相结合兼顾了激光陀螺的高精度和实时性,具有很好的应用前景。

Objective The most often used technique to lessen the lock-in effect of a ring laser gyroscope(RLG)is mechanical dithering.However,the RLG output will maintain the dither rate which must be demodulated to obtain the true body rate.The integer period sampling method,high-frequency sampling filtering method,and dither stripping method are commonly used in RLG demodulation.For high dynamic tracking applications,since the sampling frequency is low,the integer period sampling method cannot meet the requirement of high bandwidth.Thus,the high-frequency sampling filtering method is applied.Due to the characteristic of a finite impulse response(FIR)filter,the high-frequency sampling filtering method inevitably introduces a time delay,which will result in significant tracking errors.Based on the correlation of signals,the dither stripping method can remove the dither signal in real-time through the correlation cancellation algorithm.In order to solve the problem that the time delay affects the accuracy of tracking in a highly dynamic environment,this paper proposes a demodulation scheme that combines FIR filtering with dither stripping.The dither stripping method is employed in the delay period of the FIR filtering so that the RLG demodulation can be zero-latency.Methods Aiming at the case that the RLG fitted on a radar antenna concurrently rotates,a non-delay measurement method based on the combination of FIR low-pass filtering and dither stripping is creatively proposed.To avoid the accumulation of stripping errors of angular increment during the time delay period,the dither stripping is directly carried out in the angle output of RLG.The angle output of RLG after bandpass filtering is taken as the dither feedback signal and the low-frequency angular acceleration is regarded as a random walk process.Based on the correlation between the dithering feedback signal and the dithering bias signal,the gain factor of dither stripping is dynamically tracked through Kalman filtering,and the amount of dither before and after delay is calculated in real-time.Results and Discussions The RLG experiment is conducted to verify the effectiveness of the proposed nondelay measurement method.The test results reveal that the dither stripping gain factor can be tracked through the Kalman filtering in real-time(Fig.3),and the dither stripping error varies within one pulse.The method can eliminate the dither component in a FIR filter delay period of 10 ms,where cumulative angle increment error is less than two pulses(Fig.4)and stripping in the angle output can effectively limit the accumulation errors(Fig.5).Compared to the 80-order FIR filter,the dither stripping accuracy has a negligible residual error of about one pulse,corresponding to 0.466′′,which achieves accurate demodulation without latency.Conclusions In order to achieve high accuracy of RLG demodulation in a highly dynamic environment,a nondelay measurement method is proposed in this paper.The combination of FIR filtering and dither stripping gives consideration to the characteristics of high-bandwidth and real-time performance,which eliminates the negative effect of time delay introduced by FIR filtering.The experiment results indicate that the accuracy of the proposed dither stripping method is better than 0.5″during the delay period of 10 ms,which achieves zero-latency measurement.This paper provides a new demodulation scheme for RLGs applied in fast-tracking scenarios.