Tractor path tracking control based on binocular vision

In the process of field operation management, determining how to accurately realize crop row identification and path tracking control is an essential part of tractor automatic navigation. According to the linear operation in the process of cotton field management, the tractor path tracking control system was designed based on binocular vision and the pure pursuit model. A new crop row detection method based on the Census transform and the PID control algorithm with dead zone were used. First, the upper computer software was developed by C++ with the functions of parameter setting and image acquisition and processing. Second, an automatic steering controller was developed based on microprocessor MC9S12XS128 of Freescale. The control program was developed based on modular design using CodeWarrior during development of the PID-based automatic steering control strategy. Finally, a field experiment platform of tractor path tracking control was built, and field experiments under the actual cotton were conducted. The optimal visibility distance was determined by several previous experiments. When the tractor tracks the path with the optimal visibility distance in the growth environment of actual cotton crops, the mean absolute deviation of course angle was 0.95°, and the standard deviation was 1.26°; the mean absolute deviation of lateral position was 4.00 cm, and the standard deviation was 4.97 cm; the mean absolute deviation of front wheel angle was 2.99°, and the standard deviation was 3.67°. The experimental results show that (1) the crop row detection method based on Census transform can identify the crop line and plan the navigation path well, and (2) the tractor path tracking control system based on binocular vision has good stability and high control precision; thus, the control system can realize the automatic path tracking control of cotton line operation and meets the agricultural requirements of cotton field operation management.