Design and Validation of a Rotational End-Effector with a Stalk-Bending and Separation Mechanism for Apple Harvesting

Traditional gripping end-effectors often damage fruit due to structural complexity and uneven force distribution.To overcome these limitations, this study proposes a rotational end-effector that safely separates the stalk from the branch through a bending action.First, the design scheme and operating principle were established based on harvesting requirements.A rotational harvesting strategy was then formulated using statistical data, notably an average stalk length of 21.98 ± 4.33 mm.Subsequently, a composite mechanical model was developed, which enabled the derivation of critical conditions for stalk separation through theoretical analysis.Next, finite element simulations were conducted to assess the bending effects and stress distribution, confirming the end-effectorꞌs capability to protect the appleꞌs surface.Finally, the endeffector was integrated into a harvesting robot and underwent extensive field experiments.Key parameters such as motor torque, motor speed, and opening width were optimized using response surface methodology (RSM).Under conditions of a 31.43 rpm motor speed, 6.22 N•m motor torque, and a 34.16 mm opening width, the theoretical harvesting success rate reached 90.17%, while the actual success rate was 89%, demonstrating a negligible discrepancy.These results indicate that the rotational endeffector effectively preserves apple quality and holds promising prospects for practical application.