Design and Experimental Study of an Automatic Seedling Picking and Feeding Device for a Strawberry Bare-Root Seedling Transplanter

The automated transplanting of bare-root strawberry seedlings faces challenges, including a high reliance on manual feeding and a lack of adaptable equipment. Moreover, existing picking mechanisms are typically limited to plug seedlings rather than multi-stem crops. To overcome these limitations, this study proposes an automatic seedling picking and feeding system synergizing an intermittent conveying device and a manipulator. First, the physical and mechanical properties of bare-root strawberry seedlings were measured. Through radial stem compression tests, a non-destructive clamping safety threshold bounded by a bio-yield point of 28 N was determined. Secondly, an intermittent conveying device based on variable-span V-shaped supports was designed. Furthermore, based on the clamping safety threshold and spatial kinematic modeling, a seedling picking end-effector was developed. This end-effector adopts a “gather first, clamp later” operation strategy to guarantee grasping accuracy and ensure reliability by preventing seedling detachment during transportation. Finally, a system test bench was built to conduct a three-factor, three-level orthogonal experiment to investigate the effects of seedling picking frequency, gripping position, and clamping gap on operation quality. At a seedling pick-up frequency of 20 plants/min, gripping position of 25 mm, and gripping gap of 5 mm, the system reached 98% success rate in picking and feeding, validating its stability and providing core equipment and theoretical support for fully automatic strawberry transplanters.