Variable Stiffness Linear Actuator Based on Differential Drive Fiber Jamming

Variable stiffness technologies have been widely adopted in soft robotics, also combining them with different actuation technologies and demonstrating the potential to increase the range of possible applications of soft systems, such as soft continuum manipulators. However, in most cases, the variable stiffness capabilities of these soft system are far from satisfying the application requirements. With the aim to explore new possibilities to fill this gap, in this work, we present a novel variable stiffness linear actuator (VSLA) based on the combination of composite fiber jamming and the inverse pneumatic artificial muscles working principle. The differential pressure driving approach adopted to control the VSLA decouples the actuator deformation from the variable stiffness capabilities, and this makes the VSLA a suitable candidate for the realization of new kind of continuous arms. Moreover, the VSLA novel architecture introduced in this article was analytically modeled considering the interaction among constituent elements and performances in different loading conditions have been computed. The results obtained from the experimental tests validated the model goodness in terms of assumptions made and showed remarkable variable stiffness capabilities, with a maximum jamming ratio that reaches 21.3.