A Soft Robot With Variable Stiffness Multidirectional Grasping Based on a Folded Plate Mechanism and Particle Jamming

Despite good performance in grasping irregular fragile objects, soft grippers exhibiting low stiffness, and carrying capacity lack multidirectional grasping ability in the case of inclination. To address this problem, we propose a novel rigid and soft coupling variable stiffness module that employs a folded plate mechanism (FPM) to provide rigid multidirectional loading and combines it with particle jamming to achieve local variable stiffness with the characteristics of a finger grasping structure. Hence, a variable stiffness multidirectional soft grasping robot is developed to realize soft grasping and multidirectional rigid loading. The bending and stiffness control of the variable stiffness soft gripper is realized by a double-layer pneumatic driving structure with the advantages of simple control and corresponding speed. Moreover, good self-recovery is achieved with the soft outer layer since the particles can quickly return to the initial state due to partitioning of the FPM. Finally, prototype experiments verify its strong adaptability and stable multidirectional grasping ability, and experimental results show that the maximum grasping weight in each direction can be increased by more than three times with the variable stiffness.