In situations where robots work alongside humans, they must be capable of responding flexibly to unexpected external forces. To address this challenge, researchers have conducted numerous studies on soft robotics. However, most of the soft hands studied so far are powered by pneumatic pressure and can only exert pressure up to a several hundred kPa, resulting in low output. To solve this problem, we have developed a hydraulic soft hand in our previous research. In this paper, we derive the relationship between driving pressure, bending angle, and grasping force of a soft hand with a reservoir to evaluate the effect of a rubber sheet reservoir. Additionally, we experimentally show that the soft hand provides grasping flexibility when angle control is applied using the model proposed in this paper.

In this study, we develop a hydraulically-driven soft robotic hand for handling heavy vegetables in a vegetable factory and report its experimental validations. The working population in agriculture is decreasing worldwide, creating a lot of demands for the robotic automation in harvest and trans-portation of agricultural produces. In particular, a vegetable factory deals with large and heavy vegetables, e.g., cabbages, with 2–3 kg weight and 20–30 cm diameter. A soft robot hand is suitable for handling a food or vegetable; however, most of existing soft robot hands cannot generate necessary output because they are usually actuated by the air-pressure. Therefore, we employ the hydraulic actuation for our soft hand to generate 1 or 2 MPa pressure. Using the developed soft hand, we report experimental validations including basic control performance evaluation and grasping experiments assuming a vegetable factory environment.