小型山地履带拖拉机爬坡越障性能分析与试验

小型山地履带拖拉机(简称山地拖拉机)在田间行驶时,常遇到台阶、砖头、石块、田埂等障碍,严重影响其通过性及稳定性,进而引发侧滑甚至倾翻等安全问题。为此,选取最难跨越的台阶作为研究对象,对山地拖拉机爬坡越障性能进行研究。首先,对山地拖拉机爬坡时跨越台阶的运动过程进行分析,得到求解最大越障高度的计算公式;然后,基于多体动力学分析软件Recur Dyn进行了正交和单因素变量仿真试验,仿真结果表明:越障速度、坡度角和拖拉机质心位置均显著影响山地拖拉机的最大越障高度,增大越障速度和质心-支重轮距、减小坡度角和质心高度均可提高山地拖拉机的爬坡越障性能;最后,基于自主设计的山地拖拉机进行了爬坡越障田间试验。结果表明,在速度1.6 km/h、坡度角为0°～15°工况下,试验结果与理论计算及仿真试验结果基本一致,理论计算与仿真试验的最大相对误差分别为5.17%、6.47%;在坡度角大于15°工况下,理论计算与仿真试验最小相对误差分别为13.25%、19.21%。说明所得到的山地拖拉机最大越障高度计算公式及仿真模型在坡度角为0°～15°时有效。

Analysis and Test of Obstacle Negotiation Performance of Small Hillside Crawler Tractor during Climbing Process

The small hillside crawler tractors (abbreviated as SHCT) often encounter obstacles such as steps, masonry, and ridges when driving in the field, which seriously affects the passability and driving stability, and may even cause safety problems such as side slip and overturn. In order to solve this problem, the movement process of the SHCT climbing over the step was analyzed, and the mathematical model of the maximum obstacle clearance height was established. Its value was used as the evaluation index of the obstacle negotiation performance of the SHCT. Then, orthogonal and single variable simulation tests were carried out by using RecurDyn. The results indicated that the slope angle, the tractor speed and the centroid position significantly affected the maximum obstacle clearance height;and increasing the tractor speed and decreasing both the slope angle and the center height can improve the obstacle negotiation performance. Finally, a test using a self-developed 18HP SHCT for the obstacle negotiation performance was conducted. The test results showed that when the speed was 1.6km/h and the slope angle was less than 15°, the test results were basically consistent with the theoretical calculation and the simulation results. The most relative errors of the theoretical calculation and simulation were 5.17% and 6.47%, respectively;while the slope angle was larger than 15°, the minimum relative errors were 13.25% and 19.21%, respectively. The results showed that the mathematical model and simulation model of the SHCT were both effective when the slope angle was small. It could provide a theoretical reference for the safety analysis for obstacle negotiation, structural improvements and farmland using of the SHCT on the slopes less than 15°.