Design, analysis, and testing of a variable-stiffness soft grabbing robot coupling particle jamming and layer jamming

Variable-stiffness soft robots feature high flexibility in motion and high stiffness in task execution, so they are in wide demand. A coupled variable stiffening method and actuator structures based on layer jamming and particle jamming were developed. The influences of different coupled modes of particles and layers on variable stiffening were evaluated, and coupled variable-stiffness soft actuators were designed. Then, the finite element method was used to simulate the multi-airbag driving structure and variable-stiffness mechanical models were established for three coupled structures to optimize parameters influencing the stiffness. Furthermore, the prototypes of the coupled variable-stiffness soft actuators were prepared, and the test platform was built to estimate the bending performance and variable stiffening capacity. Finally, a soft grabbing robot was prepared using the coupled variable-stiffness soft actuator and application tests were performed. The theoretical analysis and test results show that the soft grabbing robot can grab objects in diverse shapes and the maximum mass of objects that can be grasped is 1.25 kg, which verifies the variable stiffening capacity of the coupled soft actuator. The research provides new theoretical and technological support for the design and application of variable-stiffness soft robots.