Kinematic design of new robot end-effectors for harvesting using deployable scissor mechanisms
Yanqin Zhao, Yan Jin, Yinglun Jian, Wen Zhao, Xiaoling Zhong
Abstract
Due to the escalating labour cost, manually harvesting of crops like apples, tomatoes and peppers, has become increasingly arduous and unsustainable. Automated harvesting employing contemporary robotic systems has emerged as a promising solution. However, a significant challenge in commercializing robot harvesting systems lies in developing effective robot end-effectors. This challenge is primarily attributed to factors such as high manufacturing costs, low picking efficiency, limited versatility, risks of fruit damage due to excessive gripping force, etc. To address these challenges, this paper proposes innovative end-effectors based on deployable mechanisms utilizing scissor mechanisms. A deployable scissor mechanism, distinguished by its expandability and foldability, can be compactly opened, and closed as an enclosable container to harvest one or multiple fruits simultaneously. Eight novel types of robot end-effector designs, each with one degree of freedom, are introduced for the first time for fruit harvesting based on deployable scissor mechanisms. These proposed end-effectors enable both direct and stem-holding separations for fruit prehension, offering two approaching orientations. Meanwhile, the proposed end-effectors can harvest different kinds of fruits of different sizes. To validate the concept, a prototype based on one of the proposed end-effector designs is manufactured by 3D printing to demonstrate its manufacturability and mobility. Simulations for automated harvesting are conducted, and harvesting efficiency analyses reveal that the robot harvesting system employing the proposed end-effector can enhance efficiency by 40% compared to the traditional approach. These newly designed end-effectors can also be applied in extended tasks such as picking sea cucumbers.