A Reconfigurable Variable Stiffness Manipulator by a Sliding Layer Mechanism

Inherent compliance plays an enabling role in soft robots, which rely on it to mechanically conform to the environment. However, it also limits the payload of the robots. Various variable stiffness approaches have been adopted to limit compliance and provide structural stability, but most of them can only achieve stiffening of discrete fixed regions which means compliance cannot be precisely adjusted for different needs. This paper offers an approach to enhance the payload with finely adjusted compliance for different needs. We have developed a manipulator that incorporates a novel variable stiffness mechanism and a sliding layer mechanism. The variable stiffness mechanism can achieve a 6.4 stiffness changing ratio with a miniaturized size (10mm diameter for the testing prototype) through interlocking jamming layers with a honeycomb core. The sliding layer mechanism can actively shift the position of the stiffening regions through sliding of jamming layers. A model to predict the robot shape is derived with verifications via an experiment. The stiffening capacity of the variable stiffness mechanism is also empirically evaluated. A case study of a potential application in laparoscopic surgeries is showcased. The payload of the manipulator is investigated, and the prototype shows up to 57.8 percentage decrease of the vertical deflection due to an external load after reconfigurations.