考虑时变扰动观测的拖拉机动力换挡过程最优控制方法

Optimal Control Method for Tractor Power-shifting Process Using Time-varying Disturbance Observer

摘要:

由于拖拉机作业工况复杂，受作业环境、土壤条件及牵引载荷等影响，动力换挡过程中的随机时变扰动易引发换挡冲击，甚至造成变速箱损坏。因此，本文提出一种考虑时变扰动观测的拖拉机动力换挡过程最优控制方法。首先，分析拖拉机动力换挡过程动态特性，建立拖拉机换挡过程动力学模型。以换挡时间、滑摩功和冲击度为换挡品质评价指标，构建换挡控制系统二次型指标函数。然后，引入高阶扰动观测器估计换挡过程中的时变扰动及其各阶导数，并结合哈密尔顿函数对线性二次型调节器（Linear quadratic regulator，LQR）求得换挡过程最优控制律。最后，基于dSPACE和Matlab/Simulink搭建了拖拉机硬件在环仿真平台，开展了不同工况下的换挡过程仿真验证。结果表明，以1LL挡升1L挡为例，运输工况和犁耕工况下，本文算法换挡时间分别为0.72、0.85s，较LQR分别减少22.58%、38.4%，经HDO算法补偿后，最大冲击度分别为16.11、8.51m/s3，虽比LQR分别增加了5.29%、2.04%，换挡顿挫差异不明显，但滑摩功控制效果显著，仅为4.61、8.82kJ，比LQR分别减少38.04%、59.17%，本文方法可有效观测抑制换挡过程中的时变扰动，提高了换挡舒适性。

Abstract:

Due to the complex working conditions of tractors, which are influenced by the working environment, soil conditions, and traction loads, random time-varying disturbances during power shifting process could easily cause shifting jerk and even damage the transmission. Therefore, an optimal control method for tractor power shifting process considering time-varying disturbance observer was proposed. Firstly, the dynamic characteristics of the tractor shift process were analyzed to establish the shifting process dynamics model. The shift time, sliding friction work, and shock degree were taken as the shifting quality indicators, and a quadratic index function of the shifting control system was constructed. Then a high-order disturbance observer (HDO) was introduced to estimate the time-varying disturbances and their derivatives during the shifting process, and the linear quadratic regulator (LQR) was derived and solved for the optimal control law of the shifting process based on the Hamiltonian function. Finally, a hardware-in-the-loop simulation platform for tractors was built based on dSPACE and Matlab/Simulink to verify the shifting process performance under different operating conditions. The results showed that taking the shift from 1LL gear to 1L gear as an example, the shifting times under the transportation and plowing working conditions were 0.72s and 0.85s respectively, which were reduced by 22.58% and 38.4% compared with that of LQR. After compensation by HDO, the maximum shifting jerks were 16.11m/s3 and 8.51m/s3, respectively, which were 5.29% and 2.04% higher than that of LQR, the shifting jerk difference was not obvious, but the sliding friction work control effect was significant, being only 4.61kJ and 8.82kJ, which were reduced by 38.04% and 59.17% compared with that of LQR. The method could effectively observe and suppress the time-varying disturbances during the shifting process, and improve the shifting comfort.