Modeling, control, and stiffness regulation of layer jamming-based continuum robots

TL;DR

This paper introduces a dynamic, control-oriented model for layer jamming-based continuum robots using port-Hamiltonian formulation, enabling real-time regulation of shape and stiffness with stability guarantees.

Contribution

It presents the first port-Hamiltonian dynamical model for LJ-based continuum robots and a passivity-based control method for simultaneous shape and stiffness regulation.

Findings

Model accurately predicts dynamic behavior of LJ robots

Control approach achieves stable decoupled regulation

Experimental results confirm theoretical stability and effectiveness

Abstract

Continuum robots with variable compliance have gained significant attention due to their adaptability in unstructured environments. Among various stiffness modulation techniques, layer jamming (LJ) provides a simple yet effective approach for achieving tunable stiffness. However, most existing LJ-based continuum robot models rely on static or quasi-static approximations, lacking a rigorous control-oriented dynamical formulation. Consequently, they are unsuitable for real-time control tasks requiring simultaneous regulation of configuration and stiffness and fail to capture the full dynamic behavior of LJ-based continuum robots. To address this gap, this paper proposes a port-Hamiltonian formulation for LJ-based continuum robots, formally characterizing the two key phenomena -- shape locking and tunable stiffness -- within a unified energy-based framework. Based on this model, we develop a passivity-based control approach that enables decoupled regulation of stiffness and configuration with provable stability guarantees. We validate the proposed framework through comprehensive experiments on the OctRobot-I continuum robotic platform. The results demonstrate consistency between theoretical predictions and empirical data, highlighting the feasibility of our approach for real-world implementation.