Legless soft robots capable of rapid, continuous, and steered jumping

Rui Chen,Jun Luo,Huayan Pu,Zean Yuan,Yu Sun,Long Bai,Liming Xin,Xinyu Zhu,Fuqiang Liu,Jianglong Guo,Li Wen,Yan Peng

doi:10.1038/s41467-021-27265-w

Abstract

Jumping is an important locomotion function to extend navigation range, overcome obstacles, and adapt to unstructured environments. In that sense, continuous jumping and direction adjustability can be essential properties for terrestrial robots with multimodal locomotion. However, only few soft jumping robots can achieve rapid continuous jumping and controlled turning locomotion for obstacle crossing. Here, we present an electrohydrostatically driven tethered legless soft jumping robot capable of rapid, continuous, and steered jumping based on a soft electrohydrostatic bending actuator. This 1.1 g and 6.5 cm tethered soft jumping robot is able to achieve a jumping height of 7.68 body heights and a continuous forward jumping speed of 6.01 body lengths per second. Combining two actuator units, it can achieve rapid turning with a speed of 138.4° per second. The robots are also demonstrated to be capable of skipping across a multitude of obstacles. This work provides a foundation for the application of electrohydrostatic actuation in soft robots for agile and fast multimodal locomotion.

Highlights

Jumping is an important locomotion function to extend navigation range, overcome obstacles, and adapt to unstructured environments
In order to use the anisotropic liquid flow to achieve forward jumping caused by unbalanced energy, we heat-sealed a HASEL like actuator into a semicircular separated HASEL (SCS-HASEL) actuator composed of two semicircular liquid pouches based on the zipping mechanism[43] and it showed better jumping performance (Supplementary Fig. 1b)
The dielectric liquid in the rear semicircular pouch of the SCS-HASEL actuator was replaced with an equal volume of air and the covered electrodes of the rear semicircular pouch were removed so that the dielectric liquid can flow anisotropically relative to the entire actuator

Summary

Introduction

Jumping is an important locomotion function to extend navigation range, overcome obstacles, and adapt to unstructured environments. The stacked quadrant donut HASELs presented by Mitchell et al.[40] can achieve continuous vertical jumping by rapidly changing internal liquid distribution with a JH of about 1.67 body heights This electrohydraulic actuation method, which can generate the energy required for jumping in a very short time without the need for a complicated energy-storing process, is a potential solution for rapid obstacle-crossing robots. The jumping caused by the partial expansion of the liquid pouch can only keep the partial actuator off the ground and the backflow of the dielectric liquid relies solely on gravity, making it slow to return to the original state after landing (Supplementary Fig. 1a) It is still challenging for HASEL jumpers to (1) achieve enhanced single-jump performance without stacking, (2) achieve rapid restoration, and (3) generate forward jumping and steered jumping. We show that LSJR’s rapid continuous jumping locomotion can cross various obstacles, including slopes, wires, single steps, continuous steps, ring obstacles, gravel mounds, and cubes of different shapes, some of which are larger than the robot

Methods

Results

Conclusion