Design and Research of an Under-actuated End-effector for Fruit and Vegetable Harvesting

In this paper, a kind of compact under-actuated end-effector was designed for harvesting fruit or vegetables with a round or round-like shape and a diameter less than 90 mm. To this aim, the end-effector structure was developed with three lingers driven simultaneously by one dc motor, while the number of degrees of freedom (DOFs) of a single finger is 3. Subsequently, its working space was analyzed by kinematics simulation. In order to achieve stable crawling under different grasping postures for this end-effector, grasping mechanical models for full knuckles, double knuckles, and single knuckle were respectively established. And simulation trials were conducted to verify the stability of the grasping force of the theoretical model. In addition, the structural parameters of the end-effector were optimized so that the forces on each knuckle are similar when grasping with all knuckles. Finally, the grasping experiments were carried out, and the results show that the performance of full-knuckles grasping fruit is better than double-knuckles or single-knuckle grasping.