Proprioceptive Origami Manipulator

TL;DR

The paper addresses the challenge of achieving proprioception and closed-loop control in tendon-driven continuum origami robots without sacrificing flexibility. It introduces a proprioceptive origami manipulator in which three conductive-thread tendons serve both as actuators and resistive sensors, with resistance changes read through a Wheatstone bridge and mapped to tendon lengths using a polynomial calibration. A Piecewise Constant Curvature (PCC) forward kinematic framework integrates these tendon-length estimates to reconstruct the end-effector pose, and the approach is validated against external motion capture. The design enhancements—including flat facets between folds to boost stiffness—and the embedded sensing enable autonomous, feedback-enabled operation in complex environments, while future work targets inverse kinematics, multi-module expansion, and exteroceptive sensing.

Abstract

Origami offers a versatile framework for designing morphable structures and soft robots by exploiting the geometry of folds. Tubular origami structures can act as continuum manipulators that balance flexibility and strength. However, precise control of such manipulators often requires reliance on vision-based systems that limit their application in complex and cluttered environments. Here, we propose a proprioceptive tendon-driven origami manipulator without compromising its flexibility. Using conductive threads as actuating tendons, we multiplex them with proprioceptive sensing capabilities. The change in the active length of the tendons is reflected in their effective resistance, which can be measured with a simple circuit. We correlated the change in the resistance to the lengths of the tendons. We input this information into a forward kinematic model to reconstruct the manipulator configuration and end-effector position. This platform provides a foundation for the closed-loop control of continuum origami manipulators while preserving their inherent flexibility.

Figures (5)

• Figure 1: A. The continuum origami manipulator with integrated proprioceptive sensing. Variations in the conductive thread's active length alter its effective resistance, which is measured via a Wheatstone bridge to infer the actuator shape. B. Fold pattern of the origami manipulator. C. The workflow for reconstructing the end effector position from sensor readings.
• Figure 2: Omnidirectional movements of the continuum origami manipulator when different combinations of three tendons are pulled. All active tendons, highlighted in yellow on top-view schematics, are pulled to the same length.
• Figure 3: A. Characterization of the axial deformation of the origami body. B. Characterization of the bending deformation of the origami body. C. Characterization of the bending angle for each tendon. D. Characterization of conductive thread under cyclic loading. The inset shows the thread strength under tensile test.
• Figure 4: A. Characterization of the resistance of the conductive thread. B. Top: Profile of the cyclic force applied to the thread using a tensile testing machine. Bottom: Corresponding resistance measurements over multiple cycles. C. Normalized resistance variation of each tendon as a function of the contraction of each edge of the origami manipulator. D. Top: Profile of cyclic motor activation. Bottom: Repeatability of sensor measurements for Tendon 2 under cyclic motor activation.
• Figure 5: A. Reconstructing tendon length during cyclic bending with increasing amplitude. Left: measured resistance, Right: tracked vs constructed length. B. Reconstruction of a closed path using the resistance sensor readings paired with the forward kinematic model.