单侧制动式转向履带底盘自主行走局部路径规划方法

Local Path Planning Method in Automatic Walking of Single-side Brake Steering Track Chassis

摘要:

针对点动控制的单侧制动式转向履带底盘在自主行走中控制精度低、转向切换频繁的问题，提出了一种基于单侧制动转向履带底盘的三切线局部路径动态规划算法，根据履带底盘转向制动力矩不可控特性，设计了“转向-直行-转向”的局部路径规划方式。三切线局部路径动态规划算法由1条直线与2条圆弧相切组成，第1段圆弧与车辆行驶方向相切，车辆沿圆弧转向逐步偏向目标航线；第2段直线与两段圆弧相切，车辆沿直线行驶逐步靠近目标航线；第3段圆弧与目标航线相切，车辆沿圆弧转向逐步与目标航向一致。车辆通过历史移动的横向偏差和航向偏差采用加权递推平均滤波计算转弯半径，判断当前所处阶段进行调整。田间自动直线行驶试验结果表明：在横向偏差0.25m、航向偏差为0°的起始状态下，以行驶速度0.4m/s前进，在该算法下行驶的横向偏差绝对值均值和横向偏差标准差分别为0.085、0.104m，分别比bang-bang算法增加23.19%、19.54%，航向偏差绝对值均值和航向偏差标准差分别为3.31°、3.74°，分别比bang-bang算法减少25.95%、25.64%，总转向控制次数为9次，比bang-bang算法减少43.75%。三切线局部路径动态规划算法适用于单侧制动式转向履带底盘，具有更高的路径跟踪精度和较低的控制频率，满足田间作业需求。

Abstract:

Aiming at the problems of low control accuracy and frequent steering switching of single-side braking steering track chassis in automatic walking, a three-tangent local path dynamic planning algorithm based on single-side braking steering track chassis was proposed. According to the uncontrollable characteristics of steering braking torque of track chassis, a local path planning method of “steering-straight-steering” was designed. The three-tangent local path dynamic planning algorithm was composed of a straight line and two arcs, the first arc was tangent to the vehicle direction, and the vehicle gradually turned to the target route along the arc. The second straight line was tangent to the two arcs, and the vehicle gradually approached the target route along the straight line. The third section of the arc was tangent to the target course, and the vehicle turned gradually to the target course along the arc. The turning radius of the vehicle was calculated by weighted recursive average filtering through the lateral deviation and heading deviation of the historical movement, and the current stage was judged for adjustment. The results of field automatic straight line driving test showed that in the initial state with a lateral deviation of 0.25m and a heading deviation of 0°, the driving speed of 0.4m/s was advanced. The mean value and standard deviation of the absolute transverse deviation of the algorithm were 0.085m and 0.104m, respectively, which were 23.19% and 19.54% higher than that of the bang-bang algorithm, respectively. The mean value and standard deviation of the absolute course deviation were 3.31°and 3.74°, respectively, which were 25.95% and 25.64% less than that of the bang-bang algorithm, respectively. The total steering control times were 9 times, which was 43.75% less than that of the bang-bang algorithm. The results showed that the three-tangent local path dynamic planning algorithm was suitable for single-side braking steering track chassis, with higher path tracking accuracy and lower control frequency, and can meet the needs of field operations.