The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensi...The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）. A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator （LO） in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio （SNR） has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement.展开更多
A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation(GPCM),which is suitable for the area where the work condition i...A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation(GPCM),which is suitable for the area where the work condition is poor and a large flow rate is required.It is difficult to control the GPCM system because the system is discrete.With consideration of the stability and speediness of the GPCM position servo control system,a control strategy is developed through the theoretical and ex-perimental analyses.The control strategy integrates the merits of Bang-Bang control,PID control and fuzzy control.With this hybrid control strategy,the electro hydraulic control system has good per-formances,and the servo control is carried out with GPCM through on-off valves.展开更多
The history of the development of Chinese telemetry is introduced in the paper. The new telemetry ground station and the new onboard space telemetry system, with the idea of systematic design and the specification, ar...The history of the development of Chinese telemetry is introduced in the paper. The new telemetry ground station and the new onboard space telemetry system, with the idea of systematic design and the specification, are described.展开更多
Brillouin optical time domain reflectometry(BOTDR)inherently involves a trade-off between sensing range and spatial resolution,particularly in long-distance applications.This paper presents an image-deconvoluted rando...Brillouin optical time domain reflectometry(BOTDR)inherently involves a trade-off between sensing range and spatial resolution,particularly in long-distance applications.This paper presents an image-deconvoluted random coding BOTDR approach to simultaneously enhance both sensing range and spatial resolution.In this method,a series of pulses modulated with random codes is employed to extend the sensing range,while the Richardson-Lucy image deconvolution algorithm is applied to refine spatial resolution.The decoding principle for random pulse detection BOTDR is systematically described,and the corresponding point spread function(PSF)is constructed.Numerical simulations are conducted to optimize coding parameters,achieving a simulated spatial resolution of 1 m over a 100 km sensing fiber.The proposed method is experimentally implemented and thoroughly evaluated.The experiment results demonstrate that,without any hardware modifications,the combination of 256-bit random coding with 1oo ns single-code width and image deconvolution extends the sensing range of BOTDR to 100.4 km with a root-mean-square error(RMSE)below 2 MHz,while achieving an actual spatial resolution of 2 m at the fiber end.These findings indicate that the proposed approach can significantly improve both the sensing range and spatial resolution in BOTDR sensing systems.展开更多
基金supported by the National High Technology Research and Development Program of China(Grant No.2012AA041203)the National Natural Science Foundation of China(Grant Nos.61377062 and 31201377)+1 种基金the Program of Shanghai Excellent Technical Leaders,China(Grant No.13XD1425400)the Doctorial Fund of Zhengzhou University of Light Industry,China(Grant No.2013BSJJ012)
文摘The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry （BOTDR）, where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）. A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator （LO） in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio （SNR） has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement.
文摘A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation(GPCM),which is suitable for the area where the work condition is poor and a large flow rate is required.It is difficult to control the GPCM system because the system is discrete.With consideration of the stability and speediness of the GPCM position servo control system,a control strategy is developed through the theoretical and ex-perimental analyses.The control strategy integrates the merits of Bang-Bang control,PID control and fuzzy control.With this hybrid control strategy,the electro hydraulic control system has good per-formances,and the servo control is carried out with GPCM through on-off valves.
文摘The history of the development of Chinese telemetry is introduced in the paper. The new telemetry ground station and the new onboard space telemetry system, with the idea of systematic design and the specification, are described.
基金Fundamental Research Program of Shanxi Province (202303021221032, 202403021222292)Key Research and Development (RD) Projects of Shanxi Province (202302150101003)。
文摘Brillouin optical time domain reflectometry(BOTDR)inherently involves a trade-off between sensing range and spatial resolution,particularly in long-distance applications.This paper presents an image-deconvoluted random coding BOTDR approach to simultaneously enhance both sensing range and spatial resolution.In this method,a series of pulses modulated with random codes is employed to extend the sensing range,while the Richardson-Lucy image deconvolution algorithm is applied to refine spatial resolution.The decoding principle for random pulse detection BOTDR is systematically described,and the corresponding point spread function(PSF)is constructed.Numerical simulations are conducted to optimize coding parameters,achieving a simulated spatial resolution of 1 m over a 100 km sensing fiber.The proposed method is experimentally implemented and thoroughly evaluated.The experiment results demonstrate that,without any hardware modifications,the combination of 256-bit random coding with 1oo ns single-code width and image deconvolution extends the sensing range of BOTDR to 100.4 km with a root-mean-square error(RMSE)below 2 MHz,while achieving an actual spatial resolution of 2 m at the fiber end.These findings indicate that the proposed approach can significantly improve both the sensing range and spatial resolution in BOTDR sensing systems.
