基于最优力位综合度的拖拉机耕深控制系统设计与试验

Design and Test of Tractor Tillage Depth Control System Based on Optimal Draft-position Comprehensive Degree

摘要:

针对拖拉机电液悬挂力位综合耕深控制过程中，人工设定力位综合度难以适应土壤条件复杂多变的作业环境问题，提出了一种基于最优力位综合度的耕深控制方法。搭建了拖拉机电液悬挂力位综合耕深控制与加载系统试验平台并采用系统辨识方法进行系统建模。针对系统等效传递函数参数不确定问题，设计了一种全局滑模控制算法，并引入反正切函数以降低系统抖振。设计全因子样本试验，采用折衷规划法建立综合作业评价指标，得到不同工况下的期望力位综合度并基于粒子群优化的最小二乘支持向量机（PSO-LSSVM）建立最优力位综合度模型。利用搭建的控制系统试验平台对控制系统效果进行了验证。结果表明，本文算法上升时间为1.06s且无明显抖振；相比于固定力位综合度为0.5的耕深控制方法，本文方法在目标耕深140、220mm的耕深偏差率分别减小19.5%和13.9%，耕深均匀性提高16.6%和11.2%。该方法可以根据土壤比阻和耕深实现力位综合度的自适应调节，面对复杂田间作业环境适应性更强，为耕深控制方法研究提供了参考。

Abstract:

Aiming at the problem that the artificial setting of comprehensive coefficient is difficult to adapt to the complex and changeable working environment of soil conditions in the process of tractor electro-hydraulic suspension tillage depth control, a tillage depth control method based on optimal draft-position comprehensive coefficient was proposed. Firstly, the test platform of tractor electro-hydraulic suspension draft-position integrated tillage depth control and loading system was built and the system was modeled by system identification method. Then aiming at the problem of uncertain parameters of the equivalent transfer function of the system, a global sliding mode control algorithm was designed, and an arc-tangent function was introduced to reduce the chattering of the system. The full factor sample test was designed, and the comprehensive operation evaluation index was established by compromise programming method. The expected draft-position comprehensive coefficient under different working conditions was obtained, and the optimal draft-position comprehensive model was established based on the least squares support vector machine optimized by particle swarm optimization algorithm (PSO-LSSVM). Finally, the effect of the control system was verified by using the built control system test platform. The results showed that the proposed algorithm achieved a rise time of 1.06s without noticeable chattering. Compared with the fixed weight-depth control method with a comprehensive coefficient of 0.5, the proposed method reduced the depth deviation rate by 19.5% and 13.9% at target depths of 140mm and 220mm, respectively, while improving depth uniformity by 16.6% and 11.2%. This method can realize the adaptive adjustment of the comprehensive coefficient according to the soil specific resistance and tillage depth, and was more adaptable to the complex field operation environment, which provided a reference for the research of tillage depth control method.