基于领航-跟随结构的大型喷灌机协同导航控制方法

针对传统圆形喷灌机、平移喷灌机存在的作业区域单一、对地块适应性差的问题，结合喷灌机圆平一体协同导航作业需求，该研究提出了一种基于领航-跟随结构的大型喷灌机协同导航控制方法。在喷灌机运动学模型的基础上，结合链式控制理论和多塔车比例积分(PI，Proportion Integration)级联控制结构，设计了主塔车路径跟踪控制律和子塔车协同跟随控制律。通过Matlab/Simulink 仿真验证了控制方法的可靠性，并以自行研制的喷灌机为载体进行田间验证试验。田间试验结果表明，平移作业模式时，主塔车平均横向偏差小于2.5 cm，主塔车航向偏差小于0.51°，子塔车平均同步偏差小于4 cm；圆形作业模式时，子塔车平均同步偏差小于5 cm。该研究提出的协同导航控制方法和参数适用于平移和圆形2种作业模式，且速度适应性较好，控制精度满足大型喷灌机协同导航喷灌作业需求，解决了传统喷灌机作业模式单一的问题，且为非规则田块的喷灌机导航控制提供技术支撑。

Collaborative navigation control method for large-scale sprinkler irrigation machine based on leader-followers structure

Abstract: A center pivot and lateral moving system in an irrigation machine has been commonly used as an energy source to move the water from the source onto the plant in precision agriculture. However, the operation of the sprinkler can also be confined to the single operation area and has low adaptability to the plot in the center pivot and lateral moving system. It is necessary to fully meet the requirements of center-lateral cooperative navigation of sprinklers during automatic operations in large scale production. In this study, an improved cooperative navigation control system was proposed using the leader-followers structure for the large-scale center pivot and lateral moving. A kinematic model was also established for the multi-tower truck of the sprinkler using the differential equations of the main and node-towers. Two motions were decomposed in a multi-tower of the sprinkler: the path tracking motion of the main tower truck, and the cascade coordinated follow-up motion of the node-towers. Specifically, the main tower controlled the leader to walk along the navigation path in the multi-tower vehicle cooperative navigation control process. The control performance of the leader was closely related to the given motion speed, navigation path curvature, lateral and heading deviation. Moreover, the path tracking system of the main tower car was designed using the chain control theory. Alternatively, the cooperative following control of the node-tower included path tracking, formation keeping, and synchronous walking control. A Proportional Integral (PI) cascade control structure was utilized to design the cooperative following control of node-towers in the multi-tower vehicles. Furthermore, the control speed of each driving wheel in the multi-tower cooperative navigation was obtained in the two modes of lateral moving and center pivot. Nevertheless, there was a response delay between the control speed of the driving wheel and the actual walking speed, when the driving wheels of each tower of the sprinkler were walking in the field. The speed range and rate of the driving wheels were limited to the ultimate performance of the collaborative navigation control system of the multi-tower truck of the sprinkler. As such, a speed transfer model was firstly constructed for the driving wheel of the sprinkler irrigation machine using Matlab/Simulink platform. The actual walking characteristics of the driving wheel were then simulated to evaluate the performance of the collaborative navigation controller. A simulation model of a cooperative navigation controller was also constructed, including the motion module of the sprinkler, the navigation path planning module, and the cooperative navigation control module. The control performance of the cooperative navigation controller was simulated and verified in both lateral moving and center pivot modes, as well as the reliability of the control system. The field test was carried out at the Xuchang Experimental Base in Henan Province, China. The self-developed sprinkler was set as the carrier. In the lateral moving mode, the average lateral and heading deviation of the main tower car were less than 2.5cm and 0.51°, respectively. The average synchronization deviations of the sub-tower cars were less than 4 and 5cm in the lateral moving and center pivot mode, respectively. Consequently, the collaborative navigation control system and parameters can be much more suitable for both lateral moving and center pivot modes. The better speed adaptability and the higher control accuracy can fully meet the needs of the large-scale circular and horizontal sprinklers for collaborative navigation and sprinkling operations.