Abstract:Automatic transplanting of strawberry plug seedlings is difficult since both the plant and root lumps are much bigger and their arches must be kept outward when they are inserted into the soil and root. The inserting forces and extraction forces were tested, then a novel test of constrained extraction and the root lump rupture were designed and carried out. It was found that the inserting forces were related to speed, depth and moisture content, and the maximum inserting forces were 21.47N and 57.09N when the inserting depths were 50mm and 100mm, respectively. The maximum extraction force was 9.64N, while the constrained extraction forces reached 10.85N and 42.5N when the fingers sliding displacements were 20mm and 40mm, respectively, but big sliding displacement was not ideal for transplanting precisely. Based on physical and mechanical characteristics of strawberry plug seedlings got from the above tests, an endeffector for automatic transplanting was developed. The endeffector was composed of two grippers and one arch reversing mechanism. The gripper had two doubleneedle fingers and the inserting angle was fixed, which was helpful to realize large inserting depth in limited mechanism dimensions and avoid bruise and tearing of plants and root lumps, respectively. Taking reducing of gripper width and swing range of connecting rod as dual objectives, optimal mechanism parameters of the gripper were obtained by performing linear programming. The arch reversing mechanism transformed distance between seedlings form picking to placing and changed the arch orientation simultaneously with cooperated limit switches and electromagnets. The experiments showed that the successful rates of extraction and nondamage picking were above 93% and 90%, respectively, when the picking acceleration was no more than 020m/s2. Otherwise,larger picking acceleration may lead to root lumps broken and fingers slid out. It was found that the arch reversing mechanism was able to transform distance between seedlings and change the arch orientation precisely. Finally, all seedlings were inserted into prepunched holes successfully and depth and upright degree were qualified, and survival rate reached 100% after 10d of transplanting. This novel endeffector was proved to be able to satisfy the need of automatic transplanting of strawberry plug seedlings.