基于高斯混合模型的履带拖拉机转弯半径控制方法

Method for Controlling Turning Radius of Crawler-type Tractors Based on GMM

履带拖拉机采用差速转向,转向可控性差,影响自动导航性能,为提高履带拖拉机自动导航的性能,以液压传动控制行星差速转向履带拖拉机为研究对象,建立履带拖拉机转弯半径数学模型。构建每个控制量下转弯半径均值和方差计算方法,建立基于卡尔曼滤波和局部加权回归的转弯半径均值和方差更新方法。分别针对直线路径跟踪和掉头建立基于高斯混合模型的履带拖拉机转弯半径控制方法。采用纯跟踪算法分别以不同的初始位置偏差进行自动导航仿真试验,得到导航轨迹、位置偏差和角度偏差。以农夫NF702型履带拖拉机为平台,分别以不同车速进行导航试验,试验结果表明,在初始航向角为0,车速分别为1.0、1.5 m/s时,导航平均误差分别为-0.62 cm和0.28 cm,导航误差绝对值极值分别为10.14 cm和8.10 cm,导航误差绝对值均值分别为2.34 cm和2.57 cm,导航均方根误差分别为3.77 cm和3.99 cm。本文提出的基于高斯混合模型的履带拖拉机转弯半径控制方法可应用到液压传动控制行星差速转向履带拖拉机自动导航领域,满足实际田间作业需求。

Crawler-type tractors use differential steering,which has poor steering controllability and affects the performance of automatic navigation.In order to improve the performance of the automatic navigation of the crawler-type tractor,hydraulic transmission control planetary differential steering crawler-type tractor was taken as the research object,and the mathematical model of the turning radius of the crawler tractor was established.A calculation method for the mean and variance of the turning radius under each control variable was constructed,and a method for updating the mean and variance of the turning radius based on Kalman filter and local weighted regression was established.Based on Gaussian mixture model a tracked tractor turning radius control method was established for straight-line path tracking and turn round respectively.The pure pursuit was used to conduct automatic navigation simulation tests with different initial position deviations,and the results of navigation trajectory,position deviation and angle deviation were obtained.Using the NF702 crawler-type tractor as experiment platform,a series of simulation tests were done at different speeds.Experiment results showed that when the initial heading angle was 0,the vehicle speed was 1.0 m/s and 1.5 m/s,the average navigation error was-0.62 cm and 0.28 cm,and the absolute value of the navigation error was 10.14 cm and 8.10 cm,respectively.The mean absolute value of navigation error was 2.34 cm and 2.57 cm,respectively,and the root mean square error of navigation was 3.77 cm and 3.99 cm,respectively.The experiment results showed that the proposed turning radius control method of crawler-type tractors based on Gaussian mixture model can be applied to the field of tracked tractor automatic navigation to meet the actual field operation requirements.