Pressure-Driven Manipulator with Variable Stiffness Structure

Abstract

The high deformability and compliance of soft robots allow safer interaction with the environment. On the other hand, these advantages bring along controllability and predictability challenges which result in loss of force and stiffness output. Such challenges should be addressed in order to improve the overall functional performance and to meet the requirements of real-scenario applications. In this paper, we present a bidirectional in-plane manipulator which consists of two unidirectional fiber-reinforced actuators (FRAs) and a hybrid soft-rigid stiffness control structure (SCS), all of them controlled by air pressure. Both controllability and predictability of the manipulator are enhanced by the hybrid soft-rigid structure. While the FRAs provide positioning and position dependent stiffness, the SCS increases the stiffness of the manipulator without position dependency. The SCS is able to increase the manipulator stiffness by 35%, 30%, and 18%, when one FRA is pressurized at 150 kPa, 75 kPa, and 0 kPa, respectively. Experiments are carried out to present the feasibility of the proposed manipulator.