基于仿生学的自走式木薯收获机优化设计方法研究

Cultivation of cassava in the tropical area of China is rising year by year, so cassava's harvesting mechanization has become an inevitable trend. However, cassava mechanization harvesting has shortcoming of low inflexible, hurting cassava easily and low digging complete rate comparing to the manual harvesting. In order to solve the above problem, the optimization design method combination of bionics for self-propelled cassava harvester is proposed to study. Based on thefunctional bionic method, the harvesting mechanism of self-propelled cassava harvester is studied, and a "dig loose-vibration soil-pulling cassava-separation" mechanisms is established, which can make the cassava harvester has better anthropomorphic harvesting function. On basis of soil mechanics, soil morphology, kinematic and dynamic analysis, the mechanics and mathematical model of the self-propelled cassava harvester's harvesting process is explored, which can provide a theoretical basis for mechanism parameters design. By simulating soil animals, bionic design of the digging shovel surface configuration is conducted, and the main structural parameters of bionic type digging shovel are optimized, which can make the digging shovel has good being buried performance, removing soil performance and reducing resistance performance. In order to improve the digging complete rate，reduce the cassava tuber broken rate and achieve lightweight design, the multi-objective optimization method is introduced to design self-propelled cassava harvester, and the mathematical modeling method and solving algorithm for optimization design are explored. The study of this project expands the application scope of bionics in agricultural machinery design, and provides a new idea for the tropical crop harvester's optimization design.

木薯在我国热带地区的种植量逐年攀升，收获机械化已成必然趋势。然而，木薯机械化收获相比人工收获存在灵活性差、易伤薯和挖净率低的问题。为解决上述问题，提出结合仿生学研究自走式木薯收获机优化设计方法。以功能仿生方法研究自走式木薯收获机的收获机理，建立一种"挖松-振土-拔薯-分离"机制，使木薯收获机具有更好的拟人收获功能；根据土壤形态结合土力学、运动学及动力学分析，探索自走式木薯收获机收获过程的力学和数学模型，为机构参数设计提供理论依据；模拟土壤动物对挖掘铲曲面构形进行仿生设计,对仿生型挖掘铲的主要结构参数进行优化设计，使挖掘铲具有良好的入土性、脱土性和减阻性；引入多目标优化方法对自走式木薯收获机整机进行设计，探索优化设计的数学建模方法和求解算法，提高整机挖净率、降低断薯率并实现轻量化。项目的研究拓展了仿生学在农机设计中的应用范围，为热带作物收获机械优化设计提供了新思路。

针对落后的木薯收获技术，本项目对自走式木薯收获机的关键部件进行结构设计、仿生设计、建立力学模型、进行有限元分析及优化设计方法研究、试制样机和田间试验，逐步突破木薯机械化收获技术的瓶颈问题，优化木薯收获机的性能。主要研究内容与结论如下：. 1. 针对现有挖掘铲的入土性、碎土性及脱土性差等问题，结合收获机理和土壤压缩破坏理论与粘附特性，研制了栅形铲、组合仿生挖掘铲及二阶曲面挖掘铲和振动铲组合的挖掘装置。根据土壤动力学和物理参数，挖掘铲作业与土壤关系，建立挖掘铲与土壤的受力模型。分析土壤粘附力、内聚力以及摩擦力等因素建立铲的牵引阻力模型。. 2.研究振动铲的工作原理，分析运动规律曲线，建立振动模型。对振动铲进行静力学校核和模态分析，获得振动铲的变形和应力分布，振动固有频率，为调节优化振动铲振动频率提供依据。. 3.通过建立夹持输送机构的速度模型，分析各关键运动学参数之间的相互之间的关系、拔起方向和取值大小。建立连续两株木薯夹持拔起速度模型，分析不发生干涉碰撞的条件，得出夹持输送机构倾角的取值范围和夹持速度比满足的条件，确定四个关键参数的最佳取值范围。. 4. 为了提高木薯收获机的工作性能，对原木薯收获机的机架进行静力学有限元分析和灵敏度分析，建立多目标优化设计模型，求解后得到了6组非劣解。在所得6组优化设计方案和原方案中，采用模糊物元法和熵权法进行优选，获得了最佳机架结构设计方案。优化设计后机架在质量减小4.29%的情况下，最大变形减小27.04%。. 5. 为了解决木薯收获机挖掘铲结构优化设计方案选型问题，提出了一种基于层次分析法的木薯挖掘铲多目标灰色关联决策方法。以静力学性能、抗振性、轻量化性能为目标函数构造木薯挖掘铲设计方案优选决策的数学模型，采用灰色关联分析法和层次分析法进行模型求解。将所提出的方法用于木薯收获机挖掘铲设计方案选型，获得了综合性能最优的仿生型木薯挖掘铲结构，为结构优化设计指明了目标函数。