Using Voice Coils to Actuate Modular Soft Robots: Wormbot, an Example

Abstract

In this study, we present a modular worm-like robot, which utilizes voice coils as a new paradigm in soft robot actuation. Drive electronics are incorporated into the actuators, providing a significant improvement in self-sufficiency when compared with existing soft robot actuation modes such as pneumatics or hydraulics. The body plan of this robot is inspired by the phylum Annelida and consists of three-dimensional printed voice coil actuators, which are connected by flexible silicone membranes. Each electromagnetic actuator engages with its neighbor to compress or extend the membrane of each segment, and the sequence in which they are actuated results in an earthworm-inspired peristaltic motion. We find that a minimum of three segments is required for locomotion, but due to our modular design, robots of any length can be quickly and easily assembled. In addition to actuation, voice coils provide audio input and output capabilities. We demonstrate transmission of data between segments by high-frequency carrier waves and, using a similar mechanism, we note that the passing of power between coupled coils in neighboring modules—or from an external power source—is also possible. Voice coils are a convenient multifunctional alternative to existing soft robot actuators. Their self-contained nature and ability to communicate with each other are ideal for modular robotics, and the additional functionality of sound input/output and power transfer will become increasingly useful as soft robots begin the transition from early proof-of-concept systems toward fully functional and highly integrated robotic systems.

Untethered soft robotics

“…One group has developed a method to induce pneumatic contraction over a longer period (70 s) by evaporating ethanol via resistive heating 30 , while others have employed combustion to achieve bending 12,31 . Deformation in these functional air chambers can also be achieved through alternative methods such as electromagnetism, thereby enabling locomotion with minimal hardware 32 . These techniques effectively remove the pneumatic tether but introduce new challenges like slow response speed, reduced output force, or limited actuation control and timing.…”

Central vs Decentralized motion control in worm robots.

“…We have proven a successful 3Rs strategy in the use of robotic hardware and software in experimental verification of neuroscience hypothesis. (Cotta et al 2006;Fang et al 2014;Chowdhury, Ansari, and Bhaumik 2017;Kanu et al 2015;Fekrmandi and Hillard 2019;Ishiguro et al 2012;Seok et al 2010;Murakami et al 2006;Omori, Hayakawa, and Nakamura 2008;Spinello and Fattahi 2017;Saga and Nakamura 2004;Ge et al 2019;Kandhari, Mehringer, et al 2019;Kandhari, Wang, et al 2019;Nemitz et al 2016;Gong et al 2016) Future work:…”

Miniature Soft Electromagnetic Actuators for Robotic Applications

“…Conventionally, such devices use rigid conductive wire inductors, such as copper wire coils, to generate time‐varying magnetic fields via applied currents, and to exert forces on permanent magnet components. While wire electromagnetic inductors may be introduced into soft materials, their rigidity can greatly limit deformability, and can reduce the durability and longevity of the materials due to stress concentrations that develop at material boundaries. Among soft conductive materials, liquid metals (LMs) including eutectic alloys Galinstan (68% Ga, 21.5% In, and 10% Ti) and gallium indium (EGaIn, 75% Ga, 25% In by mass) have attracted considerable attention for applications in stretchable electronics and soft robotics.…”