摘要
针对当前拖拉机自动导航曲线跟踪控制精度不能满足生产需要的问题,该研究提出一种基于前轮转角前馈补偿策略的变曲度路径跟踪控制方法。综合考虑农机作业速度和目标路径曲度对前视距离的影响,通过调整前视区域和计算预瞄点,动态调整前视距离和前轮转角前馈量,在追踪预瞄点的过程中,利用农机与目标路径偏差设计变曲度路径跟踪模糊控制器,通过实时调整拖拉机前轮转角补偿量减小稳态误差。以DF2204无级变速拖拉机为试验平台,设计并研发了自动导航系统,开展21组变曲度路径跟踪控制试验。试验结果表明,拖拉机以1.0、1.5、2.0和3.0 m/s速度行驶时的平均绝对误差的平均值分别为2.7、2.7、3.3和4.0 cm,均方根误差的平均值分别为3.4、3.7、4.6和5.0 cm,满足农业生产需求。所提方法可有效提高农机曲线路径跟踪精度,减少漏耕,提高农田利用率。
The current control accuracy of automatic navigation curve tracking in tractors cannot fully meet the production needs in modern agriculture.In this study,a tracking control system of variable curvature path was presented as the front wheel angle feedforward compensation.Firstly,a comprehensive evaluation was made on the influence of agricultural machinery operating speed and reference path curvature on the foresight distance.The lookahead area was then altered to compute the preview point,in order to realize the dynamic adjustment of the lookahead distance and the feedforward amount of the front wheel angle.Furthermore,the lookahead distance posed a significant effect on the speed of the vehicle.Specifically,the vehicle often traveled at a lower speed on the rugged and curved reference path,when the tractor was working on the field mechanized road or irregular fields.However,the lookahead distance was typically expressed as a linear function that related to the speed of the vehicle.The inaccurate tracking of the reference path was normally obtained due to the weak coupling,if only the speed of the vehicle without considering the curvature of the driving road on the lookahead distance.Therefore,the varying lookahead distance was proposed to depend on the curvature of the path.Meanwhile,the varying curve length of the preview point in the lookahead area was relative to the starting point of the lookahead area depending on the curvature of the reference path.Secondly,the steady-state error was often observed in the driving process of the agricultural machinery,because the pure pursuit algorithm failed to consider the deviation between the current pose and the reference path of the agricultural machinery,when tracking the preview point.An improved controller with the fuzzy control algorithm was designed to realize the compensation of the front wheel angle of agricultural machinery.Specifically,the lateral error and heading error of the agricultural machinery were used as the inputs of the fuzzy controller,and the compensation amount of the front wheel angle was used as the output.The sum of the feedforward and compensation amount of the front wheel angle were used as the control amount of the front wheel angle of the vehicle.This control amount considered the lateral error and heading error of the current position of the vehicle,together with the influence of the forward reference path on the steering of the agricultural machinery.The tracking accuracy was then greatly improved in the agricultural machinery.Taking the DF2204 continuously variable transmission tractor as the test platform,an automatic navigation system was developed to verify the practicability of the path tracking algorithm.21 sets of variable curvature path tracking experiments were carried out in Beijing Miyun Experimental Field.The results indicate that the average absolute errors were 2.7,2.7,3.3,and 4.0 cm,and the average root errors were 3.4,3.7,4.6,and 5.0 cm,respectively,when the tractor moved at 1.0,1.5,2.0,and 3.0 m/s.The tracking control approach of variable curvature path in the autonomous navigation can be expected to effectively increase the tracking accuracy of agricultural machinery curve paths and the utilization rate of farmland.
作者
吴才聪
吴思贤
文龙
陈智博
杨卫中
翟卫欣
Wu Caicong;Wu Sixian;Wen Long;Chen Zhibo;Yang Weizhong;Zhai Weixin(College of Information and Electrical,China Agricultural University,Beijing 100083,China;Key Laboratory of Agricultural Machinery Monitoring and Big Data Applications,Ministry of Agriculture and Rural Affairs,Beijing 100083,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2022年第21期1-7,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家重点研发计划项目(2021YFB3901302)。
关键词
拖拉机
自动导航
路径跟踪
变曲度
前视距离
模糊控制
tractors
automatic navigation
path tracking
variable curvature
lookahead distance
fuzzy control
