基于晶振偏移补偿的机械振动WSN同步累积误差抑制方法
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摘要
针对采用连续高频采样时钟模数转换器(ADC)的机械振动无线传感器网络(WSN)节点存在同步累积误差的问题,提出了一种基于晶振偏移补偿的同步累积误差抑制方法。基于连续高频采样时钟ADC的WSN节点,分析了同步累积误差产生原因;采用周期性信标中的帧起始界定符(SFD)信号作为同步信息,通过定时器1捕获的SFD信号间隔与参考SFD信号间隔差值确定晶振偏移补偿值,根据采样时钟与采样频率关系计算定时器2补偿后计数溢出值,由定时器2输出连续精准的高频采样时钟,消除节点间采样间隔差异,抑制同步累积误差。实验结果表明:连续采集40 s,节点间最大同步误差为0.64μs;连续采集同一信号源25 s,节点间无明显相位误差,验证了该晶振偏移补偿方法抑制机械振动无线传感器网络同步累积误差的有效性。
Aiming at the synchronous accumulated error at the nodes of mechanical vibration wireless sensor networks which adopt continuous high frequency sampling clock analog-to-digital converter(ADC), a synchronous accumulated error suppression method based on crystal offset compensation was proposed. The reason of synchronous accumulated error was analyzed. The start of frame delimiter(SFD) signal in the periodic beacon was used as the synchronization information. First, the compensation value of the crystal oscillator offset was determined according to the difference between the SFD signal interval captured by the timer 1 and the reference SFD signal interval. Then, according to the relationship between the sampling clock and the sampling frequency, the count overflow value after the compensation of the timer 2 was calculated. Finally, a continuously accurate high-frequency sampling clock was output by the timer 2, which eliminates the difference of sampling intervals between nodes and suppresses the synchronous accumulated error. The experimental results show that the maximum synchronization error between nodes when is 0.64 μs in 40 s continuous acquisition and there is no significant phase error between nodes when sampling the same signal source in 25 s continuous acquisition. The results indicate that the method based on crystal offset compensation can suppress effectively the synchronous accumulated error of the mechanical vibration wireless sensor networks.
Aiming at the synchronous accumulated error at the nodes of mechanical vibration wireless sensor networks which adopt continuous high frequency sampling clock analog-to-digital converter(ADC), a synchronous accumulated error suppression method based on crystal offset compensation was proposed. The reason of synchronous accumulated error was analyzed. The start of frame delimiter(SFD) signal in the periodic beacon was used as the synchronization information. First, the compensation value of the crystal oscillator offset was determined according to the difference between the SFD signal interval captured by the timer 1 and the reference SFD signal interval. Then, according to the relationship between the sampling clock and the sampling frequency, the count overflow value after the compensation of the timer 2 was calculated. Finally, a continuously accurate high-frequency sampling clock was output by the timer 2, which eliminates the difference of sampling intervals between nodes and suppresses the synchronous accumulated error. The experimental results show that the maximum synchronization error between nodes when is 0.64 μs in 40 s continuous acquisition and there is no significant phase error between nodes when sampling the same signal source in 25 s continuous acquisition. The results indicate that the method based on crystal offset compensation can suppress effectively the synchronous accumulated error of the mechanical vibration wireless sensor networks.
引文
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[4]施毅,张巍,孙可,等.地铁列车振动环境响应的无线传感器网络快速评定[J].振动与冲击,2017,36(2):229-234.SHI Yi,ZHANG Wei,SUN Ke,et al.Fast assessment of ambient responses induced by subway train vibration using wireless sensor networks[J].Journal of Vibration&Shock,2017,36(2):229-234.
[5]ARAUJO A,GARCIA-PALACIOS J,BLESA J,et al.Wireless measurement system for structural health monitoring with high time-synchronization accuracy[J].IEEETransactions on Instrumentation&Measurement,2012,61(3):801-810.
[6]程利军,张英堂,李志宁,等.基于时频分析及阶比跟踪的曲轴轴承故障诊断研究[J].振动与冲击,2012,31(19):73-78.CHENG Lijun,ZHANG Yingtang,LI Zhining,et al.Fault diagnose of an engine’s main bearing based on timefrequency analysis and order tracking[J].Journal of Vibration&Shock,2012,31(19):73-78.
[7]MOHANTY S,GUPTA K K,RAJU K S.Vibration feature extraction and analysis of industrial ball mill using MEMSaccelerometer sensor and synchronized data analysis technique[J].Procedia Computer Science,2015,58:217-224.
[8]裴勇,汤宝平,邓蕾,等.基于信标时序补偿的机械振动无线传感器网络同步触发方法[J].振动与冲击,2014,33(3):57-62.PEI Yong,TANG Baoping,DENG Lei,et al.A WSNmechanical vibration synchronous acquisition trigger protocol based on beacon timing compensation[J].Journal of Vibration&Shock,2014,33(3):57-62.
[9]WU Y C,CHAUDHARI Q,SERPEDIN E.Clock synchronization of wireless sensor networks[J].IEEE Signal Processing Magazine,2011,28(1):124-138.
[10]王洋,袁慎芳,董晨华,等.一种无线传感器网络分布式连续数据采集系统的同步方法[J].东南大学学报(自然科学版),2011,41(1):25-30.WANG Yang,YUAN Shenfang,DONG Chenhua,et al.Synchronous method of wireless sensor network for distributed continuous data acquisition system[J].Journal of Southeast University,2011,41(1):25-30.
[11]黄庆卿,汤宝平,邓蕾,等.机械振动无线传感器网络跨层步采集方法[J].仪器仪表学报,2014,35(5):1143-1148.HUANG Qingqing,TANG Baoping,DENG Lei,et al.Synchronous acquisition method based on cross-layer design for machine vibration wireless sensor networks[J].Chinese Journal of Scientific Instrument,2014,35(5):1143-1148.
[12]HUANG Q Q,TANG B P,DENG L.Development of high synchronous acquisition accuracy wireless sensor network for machine vibration monitoring[J].Measurement,2015,66:35-44.
[13]XIAO X,TANG B P,DENG L.High accuracy synchronous acquisition algorithm of multi-hop sensor networks for machine vibration monitoring[J].Measurement,2017,102:10-19.
[14]曾贵伟,汤宝平,邓蕾,等.机械振动无线传感器网络节点高精度数据采集方法[J].振动与冲击,2016,35(16):59-63.ZENG Guiwei,TANG Baoping,DENG Lei,et al.A high precision method for mechanical vibration data acquisition based on wireless sensor networks node[J].Journal of Vibration&Shock,2016,35(16):59-63.