环鄱阳湖区水田微耕机仿生步行轮设计及轮壤模型研究

Mini-tiller, with characteristics of small scale, lightweight, easy handling, etc., is suitable for operations in upland and water field of small area in hilly regions, and there are wide application prospects for these tillers in China. However, the study of walking wheels faces challenges in theory, method and technology in deep mud paddy field due to limitations in the environment, quality, strength and structure. On the base of analyses about the motion characteristic, buffaloes are selected as biological prototypes according to similarity theory. The walking wheel was designed using the extracting characteristic parameters, which decided stronger passing ability and smaller resistance of prototypes. The performance of walking wheels are simulated by finite element method (FEM), multi-body system dynamics and discrete element method (DEM), and the structure and material of the bionic wheel was optimized by Optistruct and ModeFrontier. According to tire dynamics theory, the project analyzed rolling mechanism of the walking wheel and established the load-deformation model, then revealed the influence of structure, material, morphology and bionic parameter on the deformation of walking wheel. Based on vehicle-terramechanics theory, the project established sinkage, motion resistance and drawbar pull mathematical model for walking wheel driving on paddy field. Finally, through Mini-tiller test, performance verification of the walking wheel was preceded and compared with steel wheel. The project can provide reference and basis for study of vehicles or robots for improving the traveling performance on soft terrain.

微耕机具有操作灵活和高性价比等优点，但受到环境、质量、强度和结构等限制，使得微耕机在深泥脚水田通过性和安全性的研究在理论和技术上存在挑战。项目在分析水田作业的畜力动物运动特征的基础上，选择耕牛作为水田步行轮仿生设计的生物原型；提取其具有高效通过能力和低阻力的特征参数，设计仿生步行轮。通过有限元法、多刚体动力学和离散元法对步行轮性能进行仿真计算，采用优化技术对其结构和材料进行优化。根据轮胎动力学理论分析步行轮的滚动机理，建立轮腿载荷模型，揭示支撑结构、材料、形貌和仿生参数对步行轮承载和变形的影响规律；根据车辆地面力学理论，结合土槽试验，建立步行轮在深泥脚水田上的沉陷、滚动阻力和推力模型。最后，通过微耕机田间试验，对模型和性能进行验证。项目研究可为提高车辆或机器人在松软土壤表面的通过性研究提供参考和依据。

微耕机具有质量轻、机型小巧、操作灵活、适应性强和高性价比等优点，是我国水田区域耕整的主要动力机械，因此开展其移动系统与水田壤相互作用机理及行走动力学特性的相关理论和技术的攻关十分必要。. 项目组采集环鄱阳湖区的水田土壤样本，测试了：粒径分布、比重、液塑限、休止角、分散度、均齐度、喷流性指数等物理参数，并进行了聚类分析，鄱阳湖中部和南部土壤在物理特性上具有一定的差异。. 测试了土槽表层水田壤的力学参数，承压参数：粘聚变形模量为1234.2 N/m^(n+1)，摩擦变形模量为104.3 N/m^(n+2)，承压指数为0.6926；剪切参数：内聚力为1887.8-2346.2 Pa，内摩擦角为10.25-11.42°；流变参数：瞬时弹性模量为7.23 N/cm和粘滞系数为127.69 N.s/cm-2；粘附参数：黏附力为1520 Pa，并建立不同含水率条件下，法向拉拔速度与土壤法向黏附力和法向压力的关系。. 设计了行星齿轮式偏心步行轮和液压伸缩式步行轮机构，并制备了液压伸缩式步行轮机构。应用仿生学原理，通过建立生物足的数字模型，完成仿生关键曲线及特征的提取，制备了仿生步行轮腿和轮足。. 土壤整备是水田壤的轮壤试验的一个重要环节，经过大量的试验和测试，整理规范了一套行之有效的土槽土壤整备流程，从基础上保证每次整备后的水田壤其土壤性质尽可能保持一致。通过轮腿水平阻力试验，发现表层水田壤中轮腿受力与轮腿入土深度成线性关系，与轮腿的水平移动速度成指数关系。通过对比常规水田轮和仿生轮的试验，仿生步行轮的驱动扭矩及挂钩牵引力均大于常规水田轮，这说明相同条件下仿生步行轮能提供更大的驱动扭矩以及挂钩牵引力。当滑转率相同时，仿生步行轮的扭矩以及挂钩牵引力跟常规叶片铁轮相比能提高约50%。. 以太沙基的半经验模型为基础，分析了11种不同轮壤理论模型，并根据水田壤土楔的破坏形式，建立了轮腿的滚动阻力模型、滑转沉陷模型、土壤推力模型和车轮扭矩预测模型，通过与试验数据的比较修正的Zeng模型和Bekker模型，其总体的预测相关系数分别为0.9288和0.9355，可为小型自走式无人水田农业作业机械牵引模型的优化提供参考。