Authors

Abstract

The accuracy of curved path-tracking for headland turning of transplanters is crucial to maintaining the row spacing precision required for rice planting. To address this issue, a method based on H-infinity state feedback control is proposed. In this method, the requirement of robustness is transformed into linear matrix inequalities (LMIs) to optimize the gain coefficients of the control law. The simulation test show that this method outperforms the Linear Quadratic Regulator (LQR) when facing uncertain parameters (longitudinal speed and cornering stiffness) and path curvature disturbance. In addition, the field test results show that when the transplanter tracks a 1/4 circular arc path with a radius of 2 meters, the mean value of the absolute lateral error and the absolute heading angle error using this controller are 0.029 m and 3.69°, respectively. The maximum absolute lateral error is 0.072 m, and 64% of the absolute lateral error are less than 0.04 m, meeting practical requirements. Compared with the LQR controller with feed forward control, the mean value of the absolute lateral error is reduced by 36%. This method meets the accuracy and robustness requirements for unmanned rice transplanter turning at the headland.

Abstract in Chinese

水稻插秧机地头转向时的曲线路径跟踪效果影响着水稻插秧机每行作业前期水稻插植的行距精度。为了提高无人插秧机曲线路径跟踪的鲁棒性，保证水田复杂环境下插秧机地头转向的精度，提出了一种基于H无穷状态反馈控制的插秧机曲线路径跟踪控制器设计方法。该方法将控制器对于不确定参数（纵向速度、轮胎侧偏刚度）和扰动项（路径曲率扰动）的鲁棒性需求转化为线性矩阵不等式（Linear Matrix Inequality，LMI）的形式，并以此为约束求解最优控制律增益系数,实现控制器对于不确定参数和扰动项的鲁棒性。仿真试验结果表明，该方法在系统存在不确定参数和扰动项时，相较线性二次调节器（Linear Quadratic Regulator，LQR）具有更好的路径跟踪效果。田间试验结果表明，插秧机在跟踪半径为2m的1/4圆弧路径时，该控制器控制下的曲线路径跟踪的横向偏差绝对值均值和航向角偏差绝对值均值分别为0.029m、3.69°，横向偏差绝对值的最大值为0.072m，绝对值小于0.04m的横向偏差占64%，满足实际需求。相较于前馈LQR控制器，横向偏差绝对值均值降低36%。该方法满足插秧机地头转向时曲线路径跟踪的精度与鲁棒性需求。