Hybrid Soft Robots Incorporating Soft and Stiff Elements

Soft robots are inherently compliant and have a solid potential for realizing human-friendly and safe robots. However, despite continued research highlighting the potential of soft robots, they remain primarily confined to laboratory settings. Inspired by spider monkeys' tails, this paper proposes a hybrid soft robot (HSR) design. We detail the design objectives and methodology to improve the controllable stiffness range and achieve independent stiffness and shape control. We extend the curve-parametric approach to obtain a kinematic model of the proposed HSR. We experimentally demonstrate that the proposed HSR has about a 100% stiffness range increase than a previous soft robot design with identical physical dimensions. In addition, we empirically map HSR's bending shape-pressure-stiffness and present an application example - a soft robotic gripper - to demonstrate the decoupled nature of stiffness and shape variations. Experimental results show that the proposed HSR can be successfully used in applications where independent stiffness and shape control is desired.