双孢菇柔性仿形采摘末端执行器设计与试验

为解决现有夹持式采摘机械手对双孢菇造成的机械损伤高、采摘损失大等问题,基于颗粒阻塞原理设计了一种双孢菇柔性仿形采摘末端执行器。首先根据双孢菇菇盖外形参数设计柔性仿形吸盘的结构,通过预试验分析末端执行器的关键参数;选定了吸盘材料和颗粒填充物的种类,通过有限元仿真验证柔性仿形吸盘的仿形能力和吸附效果,并得到柔性仿形吸盘最优的开口直径。为明确吸附负压、双孢菇直径、柔性膜厚度、颗粒直径等因素对吸附力的影响,对所试制的末端执行器进行了拉脱力试验,结果表明拉脱力与吸附负压、双孢菇直径、颗粒直径均呈线性关系,与柔性膜厚度呈非线性关系。当末端执行器中柔性膜厚度为9mm、颗粒直径为20目的石英时仿形效果最好,并与标准真空吸盘开展了对比试验,试验结果表明同等吸附力柔性仿形吸盘所需负压更低。针对尺寸范围为25~50mm的双孢菇进行了采摘试验,柔性仿形吸盘的采摘成功率为98.5%,并对采后双孢菇进行了损伤检测,柔性仿形吸盘的采摘损伤率为2.5%。结果表明,所设计的柔性仿形采摘末端执行器具备适应性强、抓取稳定、损伤率低等优点,能够满足双孢菇自动化采摘需求。

Design and Experiment of Flexible Profiling Picking End-effector for Agaricus bisporus

In order to solve the problems of high mechanical damage and large picking loss of the existing picking equipment in the automatic picking process of Agaricus bisporus, a flexible profiling picking end-effector was designed based on the principle of particle blocking. The mechanical structure of the end-effector was composed of a flexible profiling sucker and a transmission part. The flexible profiling sucker used the fluid like characteristics of the particles in the flexible membrane to profile the Agaricus bisporus with different sizes and ovalities, thereby increasing the effective contact area between the sucker and the Agaricus bisporus, improving the stability of the suction and reducing the fruit damage rate. The structural design of the end-effector was carried out according to the growth characteristics of Agaricus bisporus. The key parameters of the end-effector were determined by pre-experiment and simulation analysis. The materials of each component were selected and the prototype was trial produced. The finite element simulation was carried out for the flexible profiling sucker. The optimal opening size of the sucker was determined by finite element simulation, and the stress of the sucker was obtained. The control system and pneumatic circuit were designed for the picking logic of Agaricus bisporus. In order to clarify the influence of suction negative pressure, Agaricus bisporus diameter, flexible film thickness, particle diameter and other factors on the suction force, the pulling force test was carried out on the end-effector. The results showed that the pulling force had a linear relationship with the suction negative pressure, the diameter of Agaricus bisporus and the particle diameter, and it had a nonlinear relationship with the thickness of the flexible film. When the flexible film thickness of the end-effector was 9mm and the particle diameter was 20 mesh quartz, the suction cup holding effect was the best, and a comparative test was carried out with the ordinary silicone suction cup. The test results showed that the same suction force flexible profiling suction cup required lower negative pressure. The picking test of Agaricus bisporus with a size range of 25~50mm was carried out. The picking success rate of the flexible profiling sucker was 98.5%, and the damage detection of the postharvest Agaricus bisporus was carried out. The picking damage rate of the flexible profiling sucker was 2.5%. It had the advantages of strong adaptability, stable grasping and low damage rate, which can meet the needs of automatic picking.