Objective  To achieve low-cost agricultural machinery field positioning for small and medium-size farmland in southern China, so as to reduce labor intensity for machine operator, and improve the working efficiency of agricultural machinery.

Method  This system utilized ultra wide band (UWB) technology to accomplish real-time positioning of operating machinery, and the precise three-dimensional coordinates of the positioning labels were calculated using the localization algorithm. The position correction algorithm was then used to correct the field positioning error resulted from the body tilt of working machinery. A path planning algorithm based on AB line was designed to plan the operation path and calculate the operation deviation in a real-time manner. This system provided real-time driving assistance information for agricultural machinery operators through the visual human-computer interaction interface.

Result  In the paddy field environment, the average lateral deviations were less than 7 cm when agricultural machinery traveled along the planned path at speeds of 0.5, 1.0 and 1.5 m/s, respectively. When the travel speed was above 1.0 m/s, the average lateral deviation, the average standard deviation and the maximum lateral deviation were reduced by 52.79%, 49.82% and 50.04% respectively, based on the position correction algorithm. When the agricultural machinery equipped with the auxiliary navigation system was tested in the field transplanting experiment, the average lateral deviation between each operating trajectory and its fitting line was 5.90 cm and the average standard deviation was 3.64 cm. The average lateral deviation between each operating trajectory and its planned path was 6.98 cm and the average standard deviation was 4.95 cm.

Conclusion  The auxiliary navigation system has high positioning accuracy and good stability, as well as low-cost and strong universality, which can address the requirements of agricultural machinery field operation for small and medium-size farmland in southern China. The research results can provide a valuable reference for precise positioning of agricultural machinery in the field.