Design of Shiitake Mushroom Robotic Picking Grasper: Considering Stipe Compressive Stress Relaxation

Abstract

In order to realize the automatic picking of shiitake mushrooms and reduce the risk of damage to shiitake mushrooms in the picking process, this paper designed a shiitake mushroom picking grasper. First, this paper carries out mechanical tests of compression and stress relaxation on sections of shiitake mushroom stipes, and establishes the component stress relaxation equations of shiitake mushroom stipes. The compression mechanical characteristics of the entire mushroom stipe are then analyzed using finite element analysis, with a mean square error of less than 5% compared to actual results. Second, based on the actual picking experience, this paper proposes an “L”-shaped three-finger picking grasper, and analyzes the mechanical relationship between the grasper’s gripping force, twisting separation torque, and servo output torque. Furthermore, according to the mechanical constitutive model of mushroom stipes, the optimal twisting separation torque and corresponding servo motor output torque for the grasper are determined. The picking grasper designed in this paper was tested for picking mushrooms of different growth periods, and the test results show that the picking grasper designed in this paper is able to grasp and separate the mushrooms quickly and without damage.

Keywords

• mushroom picking
• picking grasper
• stress relaxation
• finite element analysis