Design of navigation immune controller of small crawler-type rape seeder

The middle and lower reaches of the Yangtze River are the main producing areas of winter rapeseed in China. However, due to the effects of harvesting agricultural crops, heavy soil compaction, small field, the mechanization level of rapeseed is low. The level of intelligent seeding needs to be improved. In this paper, a navigation controller for small crawler-type seeder based on immune PID was designed to solve the problem of intelligent seeding in the middle and lower reaches of the Yangtze River where the soil is sticky, the field is small. The small crawler-type rape seeder automatic navigation control system was designed. It used the small crawler-type rape seeder as the platform, and its steering system was modified by electromagnet. The high-precision BeiDou positioning module and the electronic compass was used for combined navigation to obtain the position and heading information of the crawler-type rape seeder as the input of the navigation controller. The immune PID controller was a nonlinear P controller that could adjust the proportional coefficient according to the feedback in real time. The control process was as follows. First, the plane coordinates of the start and end points of the straight path to be tracked were artificially set, and the main controller automatically calculated the distance of the target heading the start point and the end point. The weighted average algorithm was used to filter the longitude and latitude coordinates collected four times to get the current position. The controller calculated the distance deviation from the current position to the set route by the point-to-line distance formula. Taking the filtered distance deviation as an input, the target heading was calculated using the target heading correction formula distance deviation. Then, the course deviation (the deviation between the corrected target heading and the heading acquired by the electronic compass in real time) was used as an input of the immune PID controller, and the immune PID controller determined the Duty Ratio as the output u to act on the steering mechanism, achieving control of the steering of the track-type seeder. In addition, according to the characteristics of the tracked vehicle, the steering of the small crawler-type rape seeder was analyzed, and its steering model and steering angle transfer function were established. The immune PID controller was verified by Matlab simulation and experiment. Under the same parameters, the simulation showed that, compared with the conventional PID control, the immune PID control had the characteristics of fast response, small overshoot and small average tracking error. The pavement experiment showed that when the vehicle speed was 0.50 m/s, the average absolute deviation of the linear tracking of the immune PID controller was 4.2 cm, and the maximum deviation was not more than 11.9 cm. The field experiment showed that when the vehicle speed was 0.50 m/s, the average absolute deviation of the linear tracking of the immune PID controller was 5.8 cm, and the maximum deviation was not more than 15.2 cm, which was 32.6% and 18.1% higher than the conventional PID. It could better meet the requirements of the seeder navigation operation. This research provides a technical reference for the autonomous navigation of the crawler-type rape seeder.