Towards a Bioinspired Soft Robotic Gripper for Gentle Manipulation of Mushrooms

Soft Robotics showed great potential in applications where safety and compliance are key factors for the interaction of the robot with delicate objects and the environment. Mushroom harvesting nowadays is mainly performed by human harvesters and requires both dexterity and a gentle touch to preserve the quality of fresh products. Indeed, improper contact may lead to blemishes on the mushroom surface representing a loss for the market. The inherent mechanical compliance of soft grippers is a major advantage for gripping delicate produce, as the soft robotic structure can passively conform around the object to distribute its contact load, however clear specifications on the maximum forces that can be exerted are crucial for the design. This work presents a soft finger-based pneumatic gripper inspired by human hand capabilities in the manipulation of white buttom mushrooms, with the final aim of integrating into a robotic platform to automate the mushroom picking process. Bruising analysis on fresh mushrooms has been performed to evaluate the range of normal force that can be exerted without causing damage to the fresh products. The results show that mushroom cell walls can tolerate normal forces up to 7 N without breaking and exhibiting bruises. This value is significantly higher than the average normal force exerted by the expert harvester (2-3N) and it should be considered as the upper limit of the normal force which can be exerted by the gripper. These preliminary results pave the way to integrate the proposed soft gripper into mushroom shelves as the first step towards the automatizing of the harvesting process.