Research On Navigation Control Method Of Tractor Based On RTK-BDS And DR

As an important part of precision agriculture,the tractor automatic navigation technology has been widely used in automatic transplanting,seeding,fertilizing,spraying,weeding and harvesting,which can effectively reduce the labor intensity of the driver,guarantee the operation quality,improve the operation efficiency and reduce the production cost.The key technologies of automatic navigation control for tractor include positioning method,path tracking control method decision algorithm and automatic steering control method.In this paper,the John Deal 5-754 tractor was used as the test platform,RTK-BDS and DR were used for positioning,the path tracking control decision algorithms and automatic steering control algorithms were studied.(1)Aiming at the problem that the precision of RTK-BDS was greatly reduced when the satellite signal was bad,a method of integrated navigation based on RTK-BDS and DR was studied,the RTK-BDS was replaced by DR for a short time when the RTK-BDS satellite signal was not good,which reduced the influence of environmental factors on the positioning accuracy.The EKF filtering method based on tractor kinematics model was studied,which could effectively eliminate the noise of each positioning sensor.(2)According to the requirements of the tractor steering actuator,the tractor steering circuit was modified,and the electro-hydraulic steering system was designed,the speed and direction control of tractor front wheel steering hydraulic cylinder was realized.The closed loop of tractor automatic steering was designed,and the closed loop control of front wheel steering angle was realized.In order to study the dynamic response performance of the tractor automatic steering system,a mathematical model of the electro-hydraulic steering system was established,which was stable by the Routh stability criterion.(3)The fuzzy PID automatic steering control algorithm was studied.The algorithm established the fuzzy control rules between the steering angle deviation,the deviation change rate and three control parameters of PID,which optimized the control parameters of PID under different input of the steering angle deviation.The dynamic response tests and field antomatic steering tests based on the PID control algorithm and the fuzzy PID control algorithm were performed respectively.The results show that the fuzzy PID control algorithm reduced the system overshoot,shorten the transition time,which had a better control effect.(4)Based on the kinematic model and the pure tracking method,a new model of the tractor was obtained.Based on the new model and path tracking strategy,the fuzzy adaptive control decision algorithm was studied,this method dynamically adjusted the fuzzy control rules to optimize the visibility distance so that optimized target steering angle was obtained.Field experiments showed that the algorithm had good path tracking effect.(5)In order to verify the tractor navigation control method based on RTK-BDS and DR,the navigation path of the tractor was planned and the automatic navigation experiment was carried out in the field.The test results showed when the speed of the tractor was 1.80km/h-4.90km/h,the straight tracking error was less than 0.2m and head turn error was less than 0.49m for the adaptive fuzzy path tracking control decision algorithm,the optimal control effect was obtained when the speed of the tractor was 2.70km/h,and the line tracking error is less than 0.07m at this time;When the speed of the tractor speed was 2.70km/h and the visibility distance was 2m,3m,4m or 5m,the straight tracking error was less than 0.25m and head turn error was less than 0.61m,the linear tracking accuracy of this algorithm was lower than the adaptive fuzzy path tracking control method under the same speed.