Leaf Pruning End-Effector for Adaptive Positioning at the Branch–Stem Junction of Tomato Plants

Abstract

To address the needs of mechanized tomato leaf pruning, this paper presents the design of an end-effector capable of adaptive positioning at the base of the branch. This design effectively prevents infection at the cut sites of a residual branch and protects the rest of the plant from damage. The design objectives for the pruning actuator were established through the measurement of key parameters related to the morphology and mechanical properties of the lateral branch. Based on this foundation, we developed an innovative gripper featuring a spiral guide groove, enabling simultaneous axial traction and radial cutting of the branch. This design ensures that the branch–stem junction conforms to the cutting blade under shear stress, achieving the required adaptive positioning. By analyzing the mechanical properties of the lateral branch, we modeled the actuator’s traction and cutting forces to determine the key geometric parameters of the spiral fingers and the necessary driving torque. We validated the actuator’s operational effectiveness through discrete element simulation and practical application tests. The experimental results indicate that when removing the branch, a traction force of 32.5 N and a cutting force of 66.3 N are generated. Harvesting effectiveness tests conducted in the tomato field achieved a success rate of 85%. This research offers technical support for the development of handheld pruning devices and pruning robots.

Keywords

• agriculture robot
• tomato leaf pruning
• end-effector
• mechanism design
• discrete element
• field test