Design and performance evaluation of a rigid-flexible coupling end-effector for tomato picking robots

Tomato picking is a time-consuming and laborious work. The use of intelligent equipment of picking instead of manual picking can improve the production efficiency. The end-effector is an important element in direct contact with tomato fruit, and it is the key to realize automatic tomato harvest. This paper introduces a rigid-flexible coupling end-effector with a telescopic pneumatic sucker. The end-effector first extends the vacuum sucker of the adhesion mechanism to hold the target tomato and pull it out for a certain distance, and then grips the tomato with a clamping component. The target tomato picking operation was completed through the movement mode of spiral and pull combination. The physical characteristics of tomato and the mechanical characteristics of fruit stem were investigated, aiming at providing a solid theoretical basis for the design and mechanical analysis of end-effector. Then, the stability of suction and pulling force in the process of holding and pulling tomato were analyzed, so as to clarify the specifications of suction and picking parts. Finally, a composite force analysis of the adhesion mechanism and the holding mechanism was undertaken to achieve the mechanical design goal of the tomato adhesion and picking movement process. The picking performance test of the end-effector showed that the picking time of single fruit was about 5.4s and the success rate of picking could reach 88%. This study provides sufficient theoretical basis for the development of tomato picking robot and the design of end-effector.