Design of soft gripper with attached tactile sensor for underwater object grasping and force detection

Underwater robotic grasping and manipulation are greatly affected by high hydraulic pressure and dynamic water flow, thus necessitating precise force sensing. This paper presents a novel soft gripper with variable stiffness attached to the tactile sensor for underwater grasping and contact force sensing. The soft gripper utilizes an expansion support structure (ESS) to achieve variable stiffness, enabling robust structural stability to enhance the adaptability for diverse object grasping. A tactile sensor is designed using dual interlocked microstructures, filled with insulated pure water, and features annular compensation chambers (ACC) to resist varying hydraulic pressures. The tactile sensor was characterized by a broad force detection range and stable sensing performance in aquatic environments. After being attached to the soft gripper, four types of underwater objects were successfully grasped. The tactile sensor effectively detected both the contact area and forces, enabling precise identification of the grasped objects. The obtained results demonstrate the potential of our developed soft gripper with a tactile sensor for underwater object grasping and aquatic tactile force sensing.