Mechanically-Inflatable Bio-Inspired Locomotion for Robotic Pipeline Inspection

Abstract

Pipelines, vital for fluid transport, pose an important yet challenging inspection task, particularly in small, flexible biological systems, that robots have yet to master. In this study, we explored the development of an innovative robot inspired by the ovipositor of parasitic wasps to navigate and inspect pipelines. The robot features a flexible locomotion system that adapts to different tube sizes and shapes through a mechanical inflation technique. The flexible locomotion system employs a reciprocating motion, in which groups of three sliders extend and retract in a cyclic fashion. In a proof-of-principle experiment, the robot locomotion efficiency demonstrated positive linear correlation (r=0.6434) with the diameter ratio (ratio of robot diameter to tube diameter). The robot showcased a remarkable ability to traverse tubes of different sizes, shapes and payloads with an average of (70%) locomotion efficiency across all testing conditions, at varying diameter ratios (0.7-1.5). Furthermore, the mechanical inflation mechanism displayed substantial load-carrying capacity, producing considerable holding force of (13 N), equivalent to carrying a payload of approximately (5.8 Kg) inclusive the robot weight. This novel soft robotic system shows promise for inspection and navigation within tubular confined spaces, particularly in scenarios requiring adaptability to different tube shapes, sizes, and load-carrying capacities. This novel design serves as a foundation for a new class of pipeline inspection robots that exhibit versatility across various pipeline environments, potentially including biological systems.

Figures (6)

• Figure 1: The working principle of the robot proposed herein is inspired by how a parasitic wasp uses its ovipositor to inject its eggs into a host medium. (a) illustration of the parasitic wasp, adapted from esther. (b) prototype of the ovipositor-inspired robot proposed herein.
• Figure 2: Illustration of the working principle of the wasp-inspired locomotion (a) the hypothesized motion sequence of the valves that the parasitic wasp uses to transport its eggs along its ovipositor, adapted from esther; the valves retract sequentially, with one valve retracting and the other two remaining stationary, while the egg stays in place due to the higher friction of the stationary pair (step1-3). Once all the valves have been retracted, the wasp extends the entire valve assembly simultaneously, resulting in a displacement of the egg (step4). (b) the motion sequence of the ovipositor-inspired robot; a total of nine sliders are organized into three distinct groups, each consisting of three sliders. These groups operate in a coordinated, yet independent manner. The motion sequence initiates by advancing the first group of sliders forward, while the other two groups remain stationary. This pattern is then repeated with the other two groups until all groups have advanced into the forward position (step1-3). Subsequently, all three groups are pulled simultaneously, harnessing the cumulative friction force to propel the robot body forward, assuming the cumulative friction force surpasses the body inertial force (step4) (refer to the supplementary material video.1-2 for a demonstration of the motion sequence).
• Figure 3: Illustration of the robot locomotion system. (a) shows the locomotion system in its default (deflated) configuration. (b) shows the system in its inflated configuration. (c) shows the exploded view of the design featuring the main components of the system; the flexible sliders (a single slider is displayed for clarity), mechanical inflators and their associated actuation and structural support components (wires, sliders and rings).
• Figure 4: Illustration of the mechanical inflation mechanism (with a single inflator for clarity). The mechanical inflators are mounted to a stationary end and a movable end. By sliding the movable end along the axis of the robot, the inflator undergoes an elastic deformation, resulting in radial mechanical inflation (refer to the supplementary material video.3 for a demonstration of the mechanical inflation mechanism).
• Figure 5: Illustration of the experimental setups. (a) shows the experimental setup used to characterize the efficiency of the locomotion system in different conditions (refer to the supplementary material video.4 for a demonstration of the proof-of-concept experiment). (b) shows the experimental setup used to characterize the holding force of the mechanical inflation system (refer to the supplementary material video.5 for a demonstration of the mechanical inflation characterization experiment).