电力线信道噪声干扰是影响电力线通信(power line communication,PLC)的主要因素,为了研究电力线信道噪声的统计特性,以采集的场测噪声数据为依据,在时域和频域分析了低压电力线信道的噪声特性,并以此为基础,利用统计的方法建立了窄带...电力线信道噪声干扰是影响电力线通信(power line communication,PLC)的主要因素,为了研究电力线信道噪声的统计特性,以采集的场测噪声数据为依据,在时域和频域分析了低压电力线信道的噪声特性,并以此为基础,利用统计的方法建立了窄带噪声和脉冲噪声模型。通过实测噪声的统计特性对所建噪声模型进行优化,对电力线信道噪声的统计特性进行了计算和仿真。结果表明,所建立的电力线信道噪声模型与采集的实际噪声相比,时域波形几乎一致,而在频域上误差小于8.51%,从而验证了所建立模型的有效性。展开更多
Now the internal combustion engine mini-tiller has become the main and indispensable agricultural machinery in vast hilly and mountainous areas of Southwest China.However,its intense vibration may pose a big threat to...Now the internal combustion engine mini-tiller has become the main and indispensable agricultural machinery in vast hilly and mountainous areas of Southwest China.However,its intense vibration may pose a big threat to operators.As a countermeasure to the tiller vibration,a new type of electric mini-tiller powered with a group of lithium battery and a brushless DC motor was developed.The vibration signals at the handle of the tiller were tested under 6 conditions as follows:the tiller was under states of static and working in the field,at slow,medium and rapid speed,respectively.The signals were processed by means of the time domain eigenvalue analysis and the frequency spectrum analysis.The results show that with the electric motor rated speed increased from 95 to 140 r/min under static conditions,the RMS values increased 122.54%,and with the forward speed increased from 0.30 to 0.80 m/s under working conditions,the RMS values increased 201.78%.When the tiller was working,the first order vibration frequencies were 25.99 Hz,26.99 Hz and 28.99 Hz at slow,medium and rapid speed respectively,all not within 37.50-65.00 Hz,the sensitive range of human hands to the vibration frequency.In addition,according to the results of hand transmitted vibration analysis,it can be found that compared with operating the internal combustion engine mini-tiller under the same working condition,the onset of vibration-induced white finger can be delayed for 3.70 years to 10.20 years by operation of the new electric tiller.展开更多
文摘电力线信道噪声干扰是影响电力线通信(power line communication,PLC)的主要因素,为了研究电力线信道噪声的统计特性,以采集的场测噪声数据为依据,在时域和频域分析了低压电力线信道的噪声特性,并以此为基础,利用统计的方法建立了窄带噪声和脉冲噪声模型。通过实测噪声的统计特性对所建噪声模型进行优化,对电力线信道噪声的统计特性进行了计算和仿真。结果表明,所建立的电力线信道噪声模型与采集的实际噪声相比,时域波形几乎一致,而在频域上误差小于8.51%,从而验证了所建立模型的有效性。
基金supported by the Special Projects of Generic Key Technology Innovation in Chongqing's Major Industries(csct2015zdcy-ztzx80003)the Scientific Research Innovation Projects for Graduate Student of Chongqing(CYB17071).
文摘Now the internal combustion engine mini-tiller has become the main and indispensable agricultural machinery in vast hilly and mountainous areas of Southwest China.However,its intense vibration may pose a big threat to operators.As a countermeasure to the tiller vibration,a new type of electric mini-tiller powered with a group of lithium battery and a brushless DC motor was developed.The vibration signals at the handle of the tiller were tested under 6 conditions as follows:the tiller was under states of static and working in the field,at slow,medium and rapid speed,respectively.The signals were processed by means of the time domain eigenvalue analysis and the frequency spectrum analysis.The results show that with the electric motor rated speed increased from 95 to 140 r/min under static conditions,the RMS values increased 122.54%,and with the forward speed increased from 0.30 to 0.80 m/s under working conditions,the RMS values increased 201.78%.When the tiller was working,the first order vibration frequencies were 25.99 Hz,26.99 Hz and 28.99 Hz at slow,medium and rapid speed respectively,all not within 37.50-65.00 Hz,the sensitive range of human hands to the vibration frequency.In addition,according to the results of hand transmitted vibration analysis,it can be found that compared with operating the internal combustion engine mini-tiller under the same working condition,the onset of vibration-induced white finger can be delayed for 3.70 years to 10.20 years by operation of the new electric tiller.
