Design And Test Of Laser Guidance System For Field Machinery

When drivers control tractors conducting field work, walking tracks are hard to keep straight, which affects field operations, such as soil preparation, seeding, spraying, harvesting. So drivers use the row marker-assisted unit typically. However, the grooves which drew by the marker are wide and fuzzy, easy to bring the cumulative error. The row marker has been unable to meet the requirements of agricultural mechanization and agronomy. Based on laser technology and electro-optical detection technology, a laser guidance system was designed consisting of a laser emitting device and a laser receiving device. The laser emitter emitted red laser, which was received by the laser receiver installed on the tractor and converted into electric signal that was used by the LED to indicate the direction offset, assisting the driver adjusting the direction of the tractor, moving in a straight line. Therefore, completed work was as follows:The laser emitter and receiver was studied and designed. The emitter was composed of semiconductor laser and laser beam collimation compression system. The basic principle and structure of laser was researched, and on the basis of comparing different types of lasers, semiconductor laser was selected, with the laser beam collimation compression system reducing divergence angle, through the study on the characteristics of laser Gaussian beam. Laser collimator was designed with Xi’an Ling Yue Technology Co., Ltd.. On the basis of study on photoelectric detection technology, integrated laser receiving head was selected to replace photoelectric conversion and signal conditioning circuit. By receiving performance comparison of 3 different laser receiving heads, FT-099LD was selected. The design of laser receiving circuit board was completed with Altium Designer, after design and optimization of laser receiver circuit.Construction of a laser guidance system. Through modulation and leveling of the laser, the design of laser emitting device was completed. The modulated laser improved the anti-jamming capability of transmitting and receiving, as well as reduced average power consumption and extended service life. Horizontal angle of the laser beam test was carried out, which showed maximum horizontal angle was 0.51’- within 200 m, maximum deviation in vertical direction of the laser beam was 3 cm, meeting design requirements. A laser receiving device was designed. By KEIL software in C language programming, electrical signal of the laser receiver was controlled, and recognition of the position error signal was achieved with indication of LED.The influencing factors of laser propagation was researched and tested in the morning, noon, evening. The test results showed that the beam was almost no flicker within 200 m; jitter amplitude was very small; Long time stability of the laser beam pointing error was less than 0.02 mrad, which showed that the offset of the laser beam in the vertical direction was less than 4 mm within 200 m.Far-Field pattern of laser beam energy distribution was analysed and spot size adaptability was tested. The results showed laser receiver received signals in 200 m stability not appear to make two lights bright at the same time, explaining that the model and configuration of laser receiving head, peripheral circuit design was appropriate. Spot size variation did not affect system stability.Laser guidance system for road testing, in Shandong Agricultural University campus, showed that the sun light had little effect on system and when using a laser guidance system, maximum offset was 6 cm, minimum offset was 0 cm, average offset was 0.48 cm, root mean square error was 2.42 cm, and the absolute value of less than 3 cm accounted for 85%, less than 6 cm accounted for 100%. When using a row marker, maximum offset was 13 cm, minimum offset was 0.7 cm, average offset was 2.28 cm, root mean square error was 6.85 cm, and the absolute value of less than 3 cm accounted for 15%, less than 6 cm accounted for 61%. Therefore, compared with the marker, the average offset and offset extremely poor, root mean square error of the laser guidance system was smaller, and the laser guidance system improvs the linearity of the driving unit.Using the laser guidance system intelligent control using SCM including laser emitter and receiver, the unit is accurate, stable in operation and has no accumulative error, and the driving linear is improved in field work. The achievement creates favorable conditions for implementing full mechanization.