Design, Modeling and Validation of a Tendon-Driven Soft Continuum Robot for Planar Motion Based on Variable Stiffness Structures

Linda Weisheit,Welf-Guntram Drossel,Viktor Brandt,Wilhelm R Wockenfus

doi:10.1109/lra.2022.3149031

Linda Weisheit, Welf-Guntram Drossel + Show 2 more

Open Access

https://doi.org/10.1109/lra.2022.3149031

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Abstract

Robotic structures based on variable stiffness enable high-performance and flexible motion systems that are inherently safe and thus allow safe Human-Robot Collaboration. This letter presents the design of a robotic structure based on variable stiffness. A robotic manipulator is developed using three variable stiff segments based on particle jamming with a backbone architecture and two tendons for an underactuated motion control of the whole structure. By switching the structural stiffness, the manipulator is able to perform complex planar motion with only one pair of tendons, reducing the number of actuators required. A kinematic modeling approach for the calculation of the forward kinematics of this soft continuum structure is presented, and the validation on the real system is explained. The kinematic simulation is performed with a multibody simulation model (MBS) using rigid body elements in combination with rotational springs. The validation of the model is carried out with visual measurements of the real system using defined target shapes. Simulation and experimental results are discussed and compared also with a common constant curvature model. The developed MBS-model demonstrates a promising modeling approach with a position error lower 3% for the calculation of the presented manipulator under gravity.

Highlights

Multi-segmented soft continuum robots, unlike conventional rigid-link robots, are characterized by a continuous deformation, compliant structures and high dexterity and flexibility
The Modeling and Validation of the Tendondriven Soft Continuum Robotic Motion Concept was done as part of the cooperation project “BioiC - Bioinspired soft robotic systems for cognitive production” which is being carried out by the University of Naples Federico II and the Fraunhofer Institute for Machine Tools and Forming Technology
Using the example of a 3-segment robot arm, it was shown that by using this structure, combined with only two tendon actuators, various shapes can be realized by planar deformation

Summary

Introduction

Multi-segmented soft continuum robots, unlike conventional rigid-link robots, are characterized by a continuous deformation, compliant structures and high dexterity and flexibility. These features make them suitable for human-robot collaboration (HRC) or minimal invasive surgeries (MIS). To combine the advantages of flexible and inherently safe soft robots in terms of HRC and stiffer continuum robots for a better load bearing capability, many studies have been conducted on building variable stiffness robotic structures [3, 4].

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