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.