A Soft Robotic Hand Based on Bellows Actuators for Dishwashing Automation

Automation in the food services industry is not as developed as in the automotive and electrical industries. This may be because (1) the tasks involve high-speed operations in unstructured environments and (2) the lack of effective robotic end-effectors. In this letter, we focus on the automation of dishwashing operations and propose a robotic hand capable of withdrawing and grasping a dish plate from a pile, even when there is water or oil left on the plate in a post-meal scenario. The robotic hand consists of withdrawing and grasping mechanisms. Each mechanism is actuated by two bellows actuators. Soft pads with special groove patterns were fabricated and used to provide sufficient friction when they come into contact with the plate. A theoretical analysis of the withdrawing and grasping operations was performed, and an analytical model of the bellows actuator was established by considering both the pressure thrust force and the elastic force. Bellows actuators were designed based on the analysis and fabricated using both 3D printing and casting methods. Characterization of bellows actuator was performed to validate the analytical model, and agreement was found on the thrust force, but discrepancy occurred in the elastic force due to the complex structure and deformation mode of bellows. Finally, handling experiments on different plates were conducted and results demonstrated that the proposed robotic hand can successfully withdraw and grasp a plate from a pile.