DESIGN AND SIMULATION OF AN UNDERACTUATED END-EFFECTOR FOR LOW-DAMAGE SWEET PEPPER HARVESTING

This paper presents the design of a linkage-based underactuated end-effector for sweet pepper harvesting. The end-effector employs a single motor to drive a spring differential system, enabling two three-phalanx fingers to sequentially and adaptively envelop the fruit in a proximal-middle-distal order, coupled with a pneumatic cutting mechanism for peduncle separation. Biomechanical tests on sweet peppers established a safe grasping force threshold range of 0.72 N to 33.56 N. The phalanx dimensions were optimized using a genetic algorithm, ensuring the workspace covers the fruit diameter range of 70–103 mm. Static analysis determined that the push rod inclination angle should be maintained between 5°–10° to avoid dead points. ADAMS simulations verified the effectiveness of the enveloping sequence, with a peak contact force of 15.89 N remaining within non-destructive range. Prototype tests demonstrated that at a rotational speed of 90 r/min, the harvesting success rate reached 89.34%, the single-fruit harvesting time was 21.70 s, and the damage rate was 0%, confirming the effectiveness and feasibility of the proposed mechanism for low-damage sweet pepper harvesting.