东方红X-804拖拉机的DGPS自动导航控制系统

该文在东方红X-804拖拉机上开发了基于RTK-DGPS的自动导航控制系统。系统主要包括RTK-DGPS接收机、导航控制器、转向操纵控制器、电控液压转向装置和转向轮偏角检测传感器。其中转向操纵控制器、转向轮偏角检测传感器和电控液压转向装置构成转向轮偏角的闭环控制回路，该回路可根据导航控制器提供的期望转向轮偏角实现偏转角的随动控制。将拖拉机运动学模型和转向操纵控制模型相结合，建立了拖拉机直线跟踪的导航控制传递函数模型，模型的输入是横向跟踪误差，输出是期望的转向轮偏角。设计了基于PID算法的导航控制器，仿真分析了系统稳定性和动态响应性能，确定了PID控制参数的较佳取值。针对东方红X-804拖拉机转弯半径大的特点，采用跨行地头转向控制方式，提出了具体的控制流程及算法。田间试验结果表明：采用所设计的DGPS自动导航控制系统，在拖拉机行进速度为0.8 m/s时，直线跟踪的最大误差小于0.15 m，平均跟踪误差小于0.03 m，所提出的跨行地头转向控制方法对试验拖拉机具有良好的适用性。

Design of DGPS navigation control system for Dongfanghong X-804 tractor

Navigation control system based on RTK-DGPS for Dongfanghong X-804 tractor was developed. The system includes RTK-DGPS receiver, navigation controller, steering controller, electrohydraulic steering actuator and encoder sensor for the steering angle testing. The closed control loop of the steering angle is composed of steering controller, electrohydraulic steering actuator and encoder sensor. The closed loop can realize the servo control of the steering angle according to the control command from navigation controller. The control transfer function model was developed for straight trajectory tracking based on tractor kinematics model and the steering control system. The input of the transfer function is lateral tracking error and the output is commanded steering angle from navigation controller. The navigation controller was developed using PID algorithm. The stability and the responding capability of the control system were discussed and analyzed, and the control parameters were optimized. According to the characteristics of high turning radius of the tractor, a headland turning mode through spanning lines was used in the navigation control system for the tractor. The field tests showed that the maximum offset error was less than 0.15 m and the average offset error was less than 0.03 m for straight trajectory tracking at the traveling speeds of 0.8 m/s. The field tests indicated that the proposed headland turning control method is appropriated to Dongfanghong X-804 tractor.