基于倾角传感器的拖拉机悬挂机组耕深自动测量方法

在拖拉机悬挂机组耕深自动控制系统中,位置测量具有重要的作用,该文提出了一种基于倾角传感器自动测量农机具耕深的方法。通过检测提升臂的水平倾角变化,由悬挂机构几何关系和倾角传感器输出特性推导出耕深值与测量电压值之间的线性关系并换算得到实际耕深。与其他传感方式相比,该方法具有封装小、集成度高、安装和维护方便、标定易操作的特点,测量综合精度为±1.4mm;虚拟终端显示装置可直观反映耕作过程中耕深控制的实时状况,为操作者提供有效的判断依据。田间试验结果表明,耕深稳定在-200mm时的标准差为8.19,低于五轮仪测量方式,测量稳定;耕深从-100mm下降到-200mm时响应时间为3.5s,少于五轮仪测量方式,动态特性更好;耕深稳定性变异系数为3.34%,满足农艺要求。论文提出的耕深测量方法、显示界面和自动控制系统对拖拉机设计具有一定的参考意义。

Measuring tillage depth for tractor implement automatic using inclinometer

Nowadays, the motion of agricultural implements in tractors is increasingly controlled by means of electronic systems. Position measurement is a fundamental factor in tractor implement tillage depth automatic control system. The methods of linkage position measuring are divided into two kinds. One is a direct measurement that is based on external-mounted devices, such as a fifth wheel meter, or sliding palm. Another is indirect measurement that uses integrated sensors, such as a potentiometer, or camshaft. A new indirect method is proposed based on the inclinometer in this paper. The inclinometer whose package size is small is mounted on the surface of each side lifting arm. The first step is to get the relations of lifting arm level angle, tillage depth and inclinometer output voltage on the basis of the three-point hitch linkage geometric and inclinometer characteristics. The calibrated data show that the relationship between the sensor voltage output value and tillage depth is approximately linear and can thus be used as an equation to get positions. Once regulated hitch linkage or soil characteristics changes it should be used to re-calibrate the system and obtain a new formula. Compared to other methods of position measurement, by this means the measurement is convenient to be integrated, installed, maintained and calibrated, and the comprehensive precision of sensor is ±1.4 mm. Meanwhile, a virtual terminal display device for tractor implements operation was designed according to the ISOBUS standard. Its interface was classified according to the tractor implements working mode, on which various operating parameters and tillage depth curve reflects the real-time tillage depth control condition during cultivating. With this, if the tillage depth curve fluctuated due to instable working conditions, the operator may adjust set value, change the mode of control and increase or decrease tractor speed in order to achieve the purpose of stable tillage depth. A system of tillage depth measurement and tractor hitch automatic control is established. In position control mode, the field tests showed that the standard deviation is 8.19 when cultivated tillage depth value is -200 mm, and the result is lower than the fifth wheel meter method. That is to say, the inclinometer measurement method is more reliable. When the tillage depth value dropped from -100mm to -200mm, the response time of system was 3.50 s, less than the fifth wheel meter method, and the dynamic characteristic of the system was better. The variation of tillage depth stability coefficient was 3.34% when the tractor implemented actual cultivating that mets the agronomic requirements of 10%. By putting forward the tillage depth measurement, display interface and automatic control system of tractor hitch linkage, this paper has certain reference significance for tractor implement design.