An earthworm-like modular soft robot for locomotion in multi-terrain environments

Robotic locomotion in subterranean environments is still unsolved, and it requires innovative designs and strategies to overcome the challenges of burrowing and moving in unstructured conditions with high pressure and friction at depths of a few centimeters. Inspired by antagonistic muscle contractions and constant volume coelomic chambers observed in earthworms, we designed and developed a modular soft robot based on a peristaltic soft actuator (PSA). The PSA demonstrates two active configurations from a neutral state by switching the input source between positive and negative pressure. PSA generates a longitudinal force for axial penetration and a radial force for anchorage, through bidirectional deformation of the central bellows-like structure, which demonstrates its versatility and ease of control. The performance of PSA depends on the amount and type of fluid confined in an elastomer chamber, generating different forces and displacements. The assembled robot with five PSA modules enabled to perform peristaltic locomotion in different media. The role of friction was also investigated during experimental locomotion tests by attaching passive scales like earthworm setae to the ventral side of the robot. This study proposes a new method for developing a peristaltic earthworm-like soft robot and provides a better understanding of locomotion in different environments

Design and Development of Soft Earthworm Robot Driven by Fibrous Artificial Muscles

Earthworm robots have proven their viability in the fields of medicine, reconnaissance, search and rescue, and infrastructure inspection. These robots are traditionally typically hard-shelled and must be tethered to whatever drives their locomotion. For this reason, truly autonomous capabilities are not yet feasible. The goal of this thesis is to introduce a robot that not only sets the groundwork for autonomous locomotion, but also is safe for human-robot interaction. This was done by ensuring that the actuation principle utilized by the robot is safe around humans and can work in an untethered design. Artificial muscle actuation allowed for these prerequisites to be met. These artificial muscles are made of fishing line and are twisted, wrapped in conductive heating wire, and then coiled around a mandrel rod. When electrical current passes through the heating wire, the artificial muscles expand or contract, depending on how they were created. After the muscles were manufactured, experiments were done to test their functionality. Data was collected via a series of experiments to investigate the effect of various processing parameters on the performance, such as the diameter of the mandrel coiling rod, the applied dead weight, the applied current, cyclic tests, and pulse tests. After acquiring data from the artificial muscles, a prototype was designed that would incorporate the expansion and contraction artificial muscles. This prototype featured two variable friction end caps on either side that were driven via expansion muscles, and a central actuation chamber driven via an antagonistic spring and contraction artificial muscle. The prototype proved its locomotion capabilities while remaining safe for human-robot interaction. Data was collected on the prototype in two experiments – one to observe the effect of varying induced currents on axial deformation and velocity, and one to observe the effect of varying deadweights on the same metrics. The prototype was not untethered, but future research in the implementation of an on-board power source and microcontroller could prove highly feasible with this design