Design of autonomous tractor traveling along the contour-line on the slope land

研制了一种用于坡面轮廓线行走的拖拉机自动引导系统。为了实现这一系统，我们完成了五个步骤。(1)首先，提出了一个神经网络车辆模型，以获得拖拉机在坡地上的操纵性与其行为之间的关系。(2)利用基于神经网络的车辆模型，构建了等高线行驶的导航规划器。(3)将最优控制理论应用于转向控制器的设计。由于轮廓线跟踪控制中的两个变量：侧向位移和航向角是重要的，因此采用遗传算法将两者的二次型代价函数最小化。(4)第四个程序涉及使用安装的转向机构、传感器和全站仪对等高线行驶进行自动驾驶拖拉机测试。研制的轮廓线跟踪拖拉机机器人导航系统总体性能良好。(5)开发了复合控制程序，实现了拖拉机在坡面上沿矩形路径行驶的控制。为此，设计了拖拉机相对于矩形路径的坐标变换系统；2)设计了转向控制器，其中沿轮廓线、上坡和下坡方向的直线运动采用反馈控制方法；矩形路径的1/4转弯采用前馈控制方法；3)将反馈和前馈控制方法相结合，引导拖拉机沿矩形路径行驶；4)在倾斜地形上成功地进行了拖拉机自动导航系统的田间试验。

An automatic tractor guidance system for the contour-line travel on sloped terrain has been developed. To actualize this system, Five procedures were done. (1) First, a neural network (NN) vehicle model was proposed to obtain relations between the steerage and behavior of tractors on sloped terrain. (2) Second, a navigation planner for contour run is constructed by the use of NN based vehicle model. (3) Third, an optimal control theory is applied to the design of a steering controller. As two variables : lateral displacement and heading angle are important for contour line tracking control, a quadratic-form cost function of the two are minimized by genetic algorithm. (4) The fourth procedure involves using an installed steering mechanism, sensors and a Total Station, in carrying out autopilot tractor tests on contour line travel. The overall performance of the developed navigation system for the contour line tracking tractor-like robot was successful. (5) Finally, to navigate the tractor along the rectangular path on sloped terrain, Compound control procedures have been developed. For this purpose the following steps were made : 1) a coordinate transformation system was designed to determine the tractor position with respect to the rectangular path ; 2) a steering controller was also designed where feedback control method was applied for the rectilinear motions along the contour lines, uphill and downhill directions ; and a feedforward control method was developed for the quarter turns of the rectangular path ; 3) finally the feedback and feedforward control methods were compounded to guide the tractor along the rectangular path ; 4) field tests on automatic tractor guidance system were successfully conducted on sloped terrain.