A Novel Design for a Compliant Mechanism Based Variable Stiffness Grasper Through Structure Modulation

Robots utilize graspers for interacting with an environment. Conventional robotic graspers have difficulty conforming to objects of varied shape and exerting varying grasping forces. Variable stiffness soft robotic graspers provide these features but face issues such as slow response time, the requirement of external power packs for operation and low variation of stiffness. A variable stiffness compliant robotic grasper that is simple in design and operation would improve end effectors used in assistive robotics and prostheses for handling a wide array of objects. In this paper, we present the design of a novel variable stiffness compliant robotic grasper that can change its stiffness through structural transformations. Current designs utilizing structural transformations do not provide shape conformance while grasping objects. We propose a design for a soft robotic grasper using the concept of stability of truss structures. This design is capable of partially conforming to the surface of an object being grasped and can rapidly vary its stiffness utilizing compliant rotating elements embedded in the grasper jaws. The grasper behavior is modeled using finite element analysis (FEA) and validated experimentally. Our results demonstrate that structural transformation of flexible elements is a potential solution for achieving variable stiffness in a grasper.