To meet the high-efficiency and low-damage harvesting requirements for white asparagus, two novel types of end-effectors were designed to selectively harvest white asparagus. One is the transverse-cut end-effector (TCEE), while the other is the clip-cut end-effector (CCEE). To select the best harvesting scheme and achieve a suitable range in driving forces, we propose a discrete element method (DEM)-based model of the end-effectors, soil and white asparagus for the comparative analysis of a harvesting process using two end-effectors. The biomechanical properties of white asparagus were measured to determine the constraints of non-damaging harvesting, after which we derived the theoretical driving forces of the two end-effectors. Combined with an analysis of DEM simulation, the driving forces of end-effectors are quantitatively described in this paper. A test bench was built to carry out field harvesting tests. Finally, after considering the comprehensive results of the simulations and field tests, we determined TCEE to be the final harvesting component. The validated experiment showed that the relative errors between the field test and the simulation, given the driving forces of penetration, shearing and clamping, were 6%, 11.9% and 18.2%, respectively. This proves that the DEM model is capable of simulating the biomechanical properties of white asparagus, and can be used to simulate the harvesting process. The optimum combination of driving force parameters for TCEE is penetration force 200N, shearing force 4.2N and clamping force 11N. Under this scheme, the harvesting process met the requirements for high efficiency and low damage, which demonstrates the effectiveness of the white asparagus robotic harvester.

中文翻译：

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基于离散元法的收获过程中末端执行器、土壤和芦笋之间的相互作用分析

为满足白芦笋的高效、低损伤收获要求，设计了两种新型末端执行器来选择性收获白芦笋。一个是横向切割末端执行器 (TCEE)，而另一个是剪辑切割末端执行器 (CCEE)。为了选择最佳收获方案并实现合适的驱动力范围，我们提出了一种基于离散元法 (DEM) 的末端执行器、土壤和白芦笋模型，用于对使用两个末端执行器的收获过程进行比较分析. 测量白芦笋的生物力学特性以确定非破坏性收获的约束，然后我们推导出两个末端执行器的理论驱动力。结合DEM模拟分析，本文定量描述了末端执行器的驱动力。建造了一个试验台来进行田间收获试验。最后，在综合考虑模拟和现场测试的结果后，我们确定 TCEE 是最终的收获组件。经验证的实验表明，在给定穿透力、剪切力和夹紧力的情况下，现场测试和模拟之间的相对误差分别为 6%、11.9% 和 18.2%。这证明DEM模型能够模拟白芦笋的生物力学特性，可以用来模拟收获过程。TCEE 驱动力参数的最佳组合是穿透力 200N、剪切力 4.2N 和夹紧力 11N。在这个方案下，