联合收割机稻麦收获边界激光在线识别系统设计与试验

针对联合收割机收获边界在线识别问题,利用激光无损探测技术,开发了联合收割机收获边界在线识别系统。首先介绍了系统组成、激光传感器选型及工作原理,将传感器输出数据极坐标转换为直角坐标,建立稻麦轮廓特征数学模型。由于收获过程会产生大量的灰尘,会对激光探测距离及信号反射产生影响。通过与作物特征阈值比较,对受灰尘影响的错误数据进行有效识别与剔除。采用移动平均数字滤波算法,消除系统测量噪声。通过信号阶跃变化模式识别算法,实现了收获边界的在线检测,准确推算出联合收割机作业割幅,并进行了田间试验研究。试验结果表明,该系统可实现在线监测,收获边界测量误差不大于12 cm,可为联合收割机智能监控系统的实际应用提供参考。

Design and experiment of harvest boundary online recognition system for rice and wheat combine harvester based on laser detection

Abstract: At present, the combine harvester is developing towards the direction of large scale and high speed. It is more and more difficult to recognize the harvest boundary only by people''s eyesight, which is to ensure the consistency of cutting when combine harvester operates. When the harvester works in the field, it usually works in full cutting conditions, which requires the driver has high driving skills, and the whole tracking operations keep for a long time; the labour intensity of the driver and the dust of field work make it difficult to rely on the naked eye to obtain accurate boundary. Combine harvester yield monitoring system is according to the need of harvest cutting and actual speed for real-time calculation of harvest area at home and abroad, and combine harvester yield measuring system mainly relies on the operator''s input of harvesting information manually, but the actual harvest is difficult to ensure the full harvest. In the detection of combine harvester''s feeding quantity, cut width, density, and speed of operation are needed to measure for the straw obtaining. The automatic driving system of combine harvester can automatically track driving according to the harvest boundary. Therefore, the on-line detection of harvest boundary is important for intelligent monitoring system of combine harvester. Aiming at the problem of on-line recognition of harvesting boundary of combine harvester, an on-line recognition system for harvesting boundary of combine harvester was developed by laser non-destructive detection technology. Firstly, the composition of the system, and the selection and working principle of the laser sensor were introduced, and the polar coordinate of the sensor output data is converted to the right angle coordinate. The laser sensor is a 1D (one-dimensional) scanning laser rangefinder supplied by the SICK company. It uses an infra-red laser beam and it works on the principle of light propagation time measurement. A short luminous impulse is emitted. The luminous ray is then deviated by a revolving mirror and thus covers a half-plane. When the ray meets an obstacle, retro diffused light is collected by the detector. The distance from the sensor to the object is then calculated from the time interval between the emission and the reception of the impulse. As the harvest process will produce a lot of dust, it will have a laser detection distance and signal reflection. The laser ray from the sensor is retro diffused when it meets suspended particles of dust. In consequence, the measured distance is shorter than that separating the top of the vegetation from the rangefinder. Through the comparison with crop characteristic threshold, the error data affected by dust are effectively identified and eliminated. Using moving average digital filtering algorithm, system measurement noise is eliminated. Through the signal step change pattern recognition algorithm, the on-line detection of the harvest boundary is realized, and the cutting amplitude of the combine harvester is calculated accurately. The test results show that the system can realize on-line monitoring, and the measurement error is not more than 12 cm, which can provide reference for the practical application of intelligent monitoring system of combine harvester.