自动避障式葡萄藤防寒土清土机研制

针对目前葡萄藤防寒土清土机自动化程度低、清土不彻底和易伤藤等问题,该研究基于多体动力学软件RecurDyn和离散元软件EDEM耦合仿真的方法,面向中国北方砂壤土地区葡萄园内的葡萄藤防寒土清除,提出采用柔性刷子与橡胶组合的清土作业部件,并设计了一种自动避障式葡萄藤防寒土清土机,主要由机架、避障摆动机构、避障信号采集机构、控制器、清土部件、挡土板、传动部件和限深轮等部分组成,在机具前进作业过程中,通过触杆感知自动避开水泥柱,并将葡萄藤上覆盖的防寒土清除干净。采用耦合仿真试验,模拟整机避障清土的作业过程,以机具前进速度、避障油缸速度、清土部件转速和触杆转动角度阈值为试验因素,以土壤清除率为试验指标,进行四因素二次回归正交旋转中心组合模拟试验,采用Design-Expert软件对试验数据进行回归显著性分析,确定了对试验结果影响显著的因素,以土壤清除率最大为优化目标,获得了机具的最佳作业参数组合:机具前进速度0.43 m/s、避障油缸速度60 mm/s、清土部件转速550 r/min、触杆转动角度阈值10°,此时仿真优化的土壤清除率为54.65%。加工物理样机并进行田间验证试验,得到田间试验的土壤清除率为59.73%,与仿真试验的土壤清除率相对误差约为8.50%,田间试验结果与仿真优化结果基本一致,满足自动避障式葡萄藤防寒土清土作业要求。研究结果可为触土机具避障机构的整体设计及优化提供理论依据和技术支撑。

Development of automatic obstacle-avoiding grapevine cold-proof soil cleaners

Abstract: Aiming at the problems of grapevine cold-proof cleaning in sandy loam soil areas of northern China in spring, such as for example, the degree of mechanization is low, the soil is not clean thoroughly, and the grape trees are easy to be damaged, this paper proposed a cold-proof soil cleaning parts with flexible brushes and rubber, and designed an automatic obstacle-avoiding grapevine cold-proof soil cleaner based on the coupled simulation method of multi-body dynamics software RecurDyn and discrete element software EDEM. The machine was mainly composed of frame, obstacle-avoiding swing mechanism, obstacle-avoiding signal acquisition mechanism, controller, soil cleaning parts, soil retaining plate, transmission mechanism and depth wheel. The structural parameters of the key components were determined based on the analysis of the working principle of the machine. The stroke of the obstacle-avoiding cylinder was 200 mm, the obstacle-avoiding cylinder bore was 40 mm, and the turning diameter of the soil cleaning parts was 550 mm. In order to reduce the amount of simulation calculations and improve simulation efficiency, the model was simplified and imported into the multi-body dynamics software RecurDyn. Using the discrete element software EDEM to model the soil particles and a ridge with an isosceles trapezoidal cross section was obtained. Based on coupling simulation tests of RecurDyn and EDEM, the automatic obstacle-avoiding process and the soil cleaning effects of the machine were simulated. The operating parameters of the machine were set in RecurDyn software, and the process and effect of soil cleaning were simulated in EDEM software. Taking the forward speed of the machine, the velocity of the obstacle-avoiding cylinder, the rotation speed of the soil cleaning parts and the threshold value of rotation angle of the touch rod as the test factors, the soil cleaning rate was the test index, the four-factor quadratic regression orthogonal rotation center combination simulation test were carried out. Design-Expert software was used to analyze the regression significance of the test data. The results showed that the four test factors all had a significant effect on the test index. Among the interaction factors, only the rotation speed of the soil cleaning parts and the threshold value of the rotation angle of the touch rod had a significant impact on the soil cleaning rate, while the other interaction factors had no significant impact. Among the quadratic factors, the square of velocity of obstacle-avoiding cylinder had a significant effect on soil cleaning rate, while the rest factors had no significant effect. Taking the maximum soil cleaning rate as the optimization goal, the optimal operating parameters of the machine was obtained: the forward speed of the machine was 0.43 m/s, the velocity of the obstacle-avoiding cylinder was 60 mm/s, the rotation speed of the soil cleaning parts was 550 r/min, and the threshold value of the rotation angle of the touch rod was 10 °, at this time, the theoretical soil cleaning rate was 54.65%. Based on the optimization result, the physical prototype was processed. Using the iron tubes inserted into the soil to simulate the concrete column, cold-proof soil ridges similar to that in the vineyard were generated by grapevine soil burying machine, the soil cleaning tests were carried out. The test results showed that the average value of the soil cleaning rate was 59.73%, the relative error between the test result and the simulation optimization result was 8.50%, the operation effects meet the requirements of automatic obstacle-avoiding grapevine cold-proof soil cleaning. The research results can provide theoretical basis and technical support for the overall design and optimization of obstacle-avoiding mechanism of earth-touching machines and tools.