Analysis of an underactuated robotic finger with variable pinch and closure grasp stiffness

This paper presents an innovative design concept for an underactuated robotic finger which can perform adaptable closure and pinch grasping. The mechanically simple design combines an underactuated spring-loaded enclosing mechanism with a Variable Stiffness Actuator, which can be used to regulate the mechanical stiffness and interaction forces of the finger during grasping. This highly desirable property can enable the finger to be used as an adaptable and versatile gripper that can interact with its environment with minimal control effort. The design of the proposed underactuated robotic finger is presented and its main features are discussed. The interplay between the finger mechanism and its variably compliant actuation is analyzed for different grasps and load conditions, before the finger's properties are experimentally validated and the pinch and enveloping grasp capabilities demonstrated.