基于微波多普勒法的施肥质量流量检测系统研究

为了实现施肥量的精确检测,本文构建了基于微波多普勒雷达以及振动干扰抑制方法的肥料质量流量检测系统。由多普勒信号经过快速傅里叶变换处理获得肥料颗粒速度和浓度。定义速度和浓度乘积为传感器输出值,并使用最小二乘法建立传感器输出值和肥料质量流量的线性回归模型。通过对信号的统计规律进行分析,将功率谱的5倍平均值用作区分振动干扰和流量信号的阈值。在实验平台上,使用2种复合肥进行了检测,实验结果表明,肥料质量流量最大检测值可达2629.9g/min,检测相对误差不大于5％。此外,将检测系统安装在施肥机上,在水泥路上使用第3种复合肥进行了测试,由于振动影响,检测系统最大检测误差达到21.57%。使用提出的振动干扰抑制方法进行处理后,肥料质量流量检测范围在1429.1~2976.9g/min之间,相对误差不大于10.04％。因此,结合振动抑制方法,微波多普勒法的质量流量检测系统能够精确检测实验平台上和施肥机上不同肥料的质量流量。

Mass Flow Measurement System of Granular Fertilizer Based on Microwave Doppler Method

In order to achieve accurate measurement of fertilizer mass flow, a mass flow measurement system based on microwave Doppler method with a method for suppressing vibration interference was proposed. The velocity and concentration of the fertilizer particles were obtained from the Doppler signal of the granular fertilize, which was processed by using the fast Fourier transform, and the product of the velocity and concentration was defined as the sensor output value. Then, a linear regression model of the sensor output value and fertilizer mass flow was established by using the least squares method. By analyzing the statistical law of the signal, the five times mean value of power spectral density was used as the threshold to distinguish interference and signal. The fertilizer mass flow was changed by changing the rotating velocity of the fertilizing shaft. For laboratory environment, the mass flow of two types of fertilizers was measured. The experimental results showed that for two types of fertilizers, the max measurement value of the system can reach 2629.9g/min, and the relative errors of the microwave method were not more than 5%. In addition, the measurement system was installed on the fertilizing machine. An experiment was carried out by using the third type of fertilizer on the cement road beside the farmland. The analysis showed that the interference caused by vibration made the relative errors of measurement larger. The maximum relative error reached 21.57%. In order to improve the measurement accuracy, the proposed vibration interference suppression method was used. After the interference suppression, the fertilizer mass flow measurement range was between 1429.1g/min and 2976.9g/min, and the relative error was not more than 10.04%. The constructed system can accurately detect the mass flow of different fertilizers in the laboratory and under fertilizing machine conditions.