Session: 06-06: Bioinspired Structures

Paper Number: 111235

111235 - Hybrid Soft-Rigid Joint With Inherent Sensing and Actuation Capabilities Based on Rolled Dielectric Elastomers 

Modern robotics development strives to achieve a save human robot collaboration, which eliminates the danger for humans working hand in hand with robotic systems. Therefore, hard, and soft robotic systems exist with individual properties. The rigid nature of hard robots enables a straight forward kinematic coupling and thus allow for robust trajectory planning in controlled environments [1]. If however the robot works in an unpredictable surrounding with impact from many directions and inconvenient motions, hybrid soft-rigid robots come with an advantage due to their better impulse distribution throughout the tension networks [2]. Their joints just like in the human body and more specific the musculoskeletal system consisting of bones, cartilage, ligaments, tendons and connective tissues for example can be mimicked by tensegrity structures using compression and tension elements. [3]

Traditionally, the tension structures are built by passive wires unable to give information about the state of the system or to exite an actuation from within. Using dielectric elastomers (DE) to distribute tension forces both can be achieved within the structure itself. The sensing as well as actuation properties of DEs can be implemented into the system to induce movement and give feedback. Its flexibility allows the design of different shapes such like membrane actuators as the most often used shape. Their large deformation capabilities of over 100% linear strain enable different tensegrity structures like rod or cable based DE-tensegrities. [4]

Membrane-based DEs usually come with a 30-50 µm thick silicone and therefore result in a low stiffness system. Stacking of membranes can compensate for that but comes with higher challenges for the manufacturing and assembling process as well as generates and covers a bigger surface over the structure to work. In order to integrate slim DEs that can not only be used as actuators and sensors but also assume the role of passive tension elements the membrane is being rolled up to be used as a stiffer, centrical elastomer beam, which is called a rolled dielectric elastomer (RDE).

This work concentrates on the building and testing of a tensegrity joint based on a table concept with inherent sensors and actuators within the tension elements. These smart elements are being characterized and their feasibility as tensegrity tension structures with a focus on the sensory properties are investigated. Further first actuation tests are being conducted and allow a detailed outlook on the next development steps towards a universal sensing and actuating soft-rigid joint.

Literature

[1]          E. Jung, V. Ly, A. Buderi, E. Appleton, and M. Teodorescu, “Design and Selection of Muscle Excitation Patterns for Modeling a Lower Extremity Joint Inspired Tensegrity,” Proc. - 3rd IEEE Int. Conf. Robot. Comput. IRC 2019, no. March, pp. 282–287, 2019.

[2]          S. Lessard, J. Bruce, E. Jung, M. Teodorescu, V. Sunspiral, and A. Agogino, “A lightweight, multi-axis compliant tensegrity joint,” Proc. - IEEE Int. Conf. Robot. Autom., vol. 2016-June, pp. 630–635, 2016.

[3]          X. Xie, D. Xiong, and J. Z. Wen, “A wrist-inspired suspended tubercle-type tensegrity joint with variable stiffness capacity,” Bioinspiration and Biomimetics, vol. 18, no. 1, 2023.

[4]          S. Watanabe, Y. Ikemoto, and J. Shintake, “Modeling and Characterization of Tensegrity Structures Integrating Dielectric Elastomer Actuators,” Adv. Eng. Mater., 2022.

Presenting Author: Julian Neu Center for Mechatronics and Automation Technology (ZeMA) gGmbH

Presenting Author Biography: Julian Neu
Center for Mechatronics and Automation Technology (ZeMA) gGmbH