Soft pneumatic grippers: Topology optimization, 3D-printing and experimental validation

This paper presents a systematic topology optimization framework for designing a soft pneumatic gripper (SPG), explicitly considering the design-dependent nature of the actuating load. The load is modeled using Darcy's law with an added drainage term. A 2D soft arm unit is optimized by formulating it as a compliant mechanism design problem using the robust formulation. The problem is posed as a min-max optimization, where the output deformations of blueprint and eroded designs are considered. A volume constraint is imposed on the blueprint part, while a strain-energy constraint is enforced on the eroded part. The MMA is employed to solve the optimization problem and obtain the optimized soft unit. Finite element analysis with the Ogden material model confirms that the optimized 2D unit outperforms a conventional rectangular design under pneumatic loading. The optimized 2D unit is extruded to obtain a 3D module, and ten such units are assembled to create a soft arm. Deformation profiles of the optimized arm are analysed under different pressure loads. Four arms are 3D-printed and integrated with a supporting structure to realize the proposed SPG. The gripping performance of the SPG is demonstrated on objects with different weights, sizes, stiffness, and shapes.