基于晶振偏移补偿的机械振动WSN同步累积误差抑制方法

Synchronous accumulated error suppression method based on the crystal offset compensation for mechanical vibration wireless sensor networks

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.