Abstract
Earthworm-like robots have received great attention due to their prominent locomotion abilities in various environments. In this research, by exploiting the extraordinary three-dimensional (3D) deformability of the Yoshimura-origami structure, the state of the art of earthworm-like robots is significantly advanced by enhancing the locomotion capability from 2D to 3D. Specifically, by introducing into the virtual creases, kinematics of the non-rigid-foldable Yoshimura-ori structure is systematically analyzed. In addition to exhibiting large axial deformation, the Yoshimura-ori structure could also bend toward different directions, which, therefore, significantly expands the reachable workspace and makes it possible for the robot to perform turning and rising motions. Based on prototypes made of PETE film, mechanical properties of the Yoshimura-ori structure are also evaluated experimentally, which provides useful guidelines for robot design. With the Yoshimura-ori structure as the skeleton of the robot, a hybrid actuation mechanism consisting of SMA springs, pneumatic balloons, and electromagnets is then proposed and embedded into the robot: the SMA springs are used to bend the origami segments for turning and rising motion, the pneumatic balloons are employed for extending and contracting the origami segments, and the electromagnets serve as anchoring devices. Learning from the earthworm’s locomotion mechanism--retrograde peristalsis wave, locomotion gaits are designed for controlling the robot. Experimental tests indicate that the robot could achieve effective rectilinear, turning, and rising locomotion, thus demonstrating the unique 3D locomotion capability.
Highlights
In recent years, earthworm-like locomotion robots have received great attention due to their excellent mobility in narrow space and unstructured environments, enabling many potential applications such as pipe cleaning (Tanise et al, 2017; Fang et al, 2014; Adams et al, 2018), gastrointestinal examination (Wang et al, 2008; Rodríguez et al, 2006), and battlefield surveillance (Fields et al, 2009)
Yoshimura Based Earthworm-like Robot consists of a large number of independent working segments separated by septa (Edwards and Bohlen, 1996); 2) each segment possesses circular and longitudinal muscles that work antagonistically to each other (Alexander, 2013), giving rise to interrelated radial and axial deformations of the segment; 3) the bulk of segments have bristle-like setae that can help to anchor parts of the body to the working media during movement (Edwards and Bohlen, 1996)
Based on the model of a single Yoshimura-ori layer, we investigate the reachable workspace of the Yoshimura-ori structure without considering the effect of gravity
Summary
Earthworm-like locomotion robots have received great attention due to their excellent mobility in narrow space and unstructured environments, enabling many potential applications such as pipe cleaning (Tanise et al, 2017; Fang et al, 2014; Adams et al, 2018), gastrointestinal examination (Wang et al, 2008; Rodríguez et al, 2006), and battlefield surveillance (Fields et al, 2009). A rigid robot segment can be manufactured and assembled relatively ; it could adapt to various types of actuators (e.g., shape memory alloys (SMA) (Kim et al, 2006) and servomotors (Fang et al, 2014; Kim et al, 2006)), while its deformability is often limited For the latter, the robot body is always made up of continuously deformable elements (e.g. coupled cables (Daltorio et al, 2013; Kandhari et al, 2018)) or soft/extensible materials (e.g. rubber and silicone (Harigaya et al, 2013; Calderón et al, 2019)). To advance the state of the art, a new type of Yoshimura-ori-based earthworm-like robot with unique 3D spatial locomotion capability is developed This is because the Yoshimura-ori structure possesses excellent axial and bending deformability, which can be exploited to break through the current limitations in achieving turning and rising motions in earthworm-like robots. Experimental tests indicate that the robot could perform effective rectilinear, turning, and rising locomotion, successfully expanding the locomotion ability from 2D to 3D
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